August 10 Call Stream: CLICK HERE

 

Table 1.  Rainfall totals between June 1, 2021, and August 9, 2021 from Cornell NEWA system. Find your local station today: http://newa.cornell.edu. Historical average rainfall between June and August is 12”.

Regional update
After heavy rains over the last five days, weather across the region will remain hot and humid for the next few days before cooling off with highs in the upper 70s over the weekend.  Cooler nights should help fruit put on good color and the recent rainfall for some will be good for fruit sizing.

Codling moth
The timing of our second-generation codling moth flight continues to be less predictable than first generation with biofixes occurring as early as July 9 and as late as July 25. There are a few instances of second generation biofixes in early August. The range in these dates reflects how well codling moth was controlled during first generation and when or if there were any wash-off events or missed sprays during the first generation.  For example, an early July biofix correlates to survival of moths earlier during the first generation, whereas a later biofix indicates good control early in the generation, but moth survival later during the first generation. Generally, the degree days from first-generation biofix are less important and especially when there is successful reproduction within the orchard from the 1st generation. Orchards that experienced an early second-generation biofix are between 600 and 700 DD, just passing peak egg hatch.  Where the biofix occurred later, these orchards are anywhere between 350 and 500 DD, or just entering peak egg hatch.  All growers should be monitoring codling moth traps into the first week of September and should remember that any moths that fly after August 20^th, will be hatching out in early September.

Timing August cover sprays
Many growers are considering the need to reapply after the recent rainstorms and with the possibility of these storms dropping intense rainfall in a short amount of time.  The need to maintain long-lasting residues for 10 – 14 days is largely dependent on your target pest. Codling moth, lesser appleworm and obliquebanded leafroller require sustained pesticide residue to manage these pests and should be reapplied after rains to maintain the effective residue.  Conversely, insecticides may only need to be active for 12 hours to a few days to effectively suppress populations of Japanese beetle, apple maggot, mites or woolly apple aphid. Fungicide applications for summer diseases and bitter rot may not need to be reapplied immediately after a heavy rainstorm. Once an application of Topsin, Flint or Merivon is applied, the fungicide moves into the plant tissue and eradicates the infection of sooty blotch and flyspeck, or bitter rot. If you are protecting against these diseases with Captan or OMRI products such as potassium bicarbonate or Regalia, these would need to be reapplied after heavy rains wash off residues.  A terpene-based stickers, e.g., Attach or Nu Film P, could improve rainfastness for certain pests including OBLR and Japanese beetle, but would not likely maintain enough residue for codling moth or apple maggot, especially after four inches of rain.

Apple maggot activity has been minimal over the last few weeks, but with the recent rain, there is a good likely hood of growers catching late apple maggot at the end of August that would require treatment. Even if it is unlikely, you would make a late spray, it is really important to maintain trapping into September to prevent any surprises and develop an understanding of what kind of overwintering population may emerge. Where codling moth has been managed using mating disruption or if trap captures have been low, continue to monitor lesser appleworm with either an LAW or OFM lure. OFM is typically not a problem here, but LAW is present. If these numbers are high enough, e.g., ten or more a week, you may want to consider OFM MD next year and should consider a larvacide this year. Note: OFM/LAW are much easier to disrupt than CM.

A note on neonicotinoids: Assail (acetamiprid) is one of our best active ingredients to achieve combined management of apple maggot and codling moth.  However, it is very easily washed off, which is counter intuitive, since we consider that neonicotinoids are absorbed into the fruit.  If Assail is applied for JPB or apple maggot, a half of rain will leave enough residue to manage these pests, however, after half to one inch of rain, a half inch of rain after 7 days, will not leave enough residue for codling moth.

Organic codling moth management
Research trials have found that adding brown sugar and yeast to tank mixes of Virosoft, Madex HP, (Cydia pomonella granulosis virus), similar to adding sugar to improve efficacy of imidacloprid for AM, greatly improves the efficacy of this product.  The research was completed by Alan Knight, USDA Research Entomologist based out of Yakima, WA.  In his trials, Knight mixed bread yeast, sugar with Virus and tested against codling moth and found in both lab assays and field trials it resulted in significantly less damage from codling moth and reduced overwintering moths. The trials used 3 lb. of each material (brown sugar, yeast) per 100 gallons of water.  Organic and conventional growers could consider this if there are late CM, since these products have a zero day PHI.   

Secondary pests
Besides the direct fruit pests, we are seeing some resurgence of various secondary pests, including European red mites (ERM), woolly apple aphids (WAA), San Jose scale (SJS) and Japanese beetle (JPB). These pest populations are often found with various bio-control species predating or parasitizing them, but since temperatures in August are hotter than normal, the pests are completing their life cycles faster and the biocontrolâ€s are not keeping up, in some instances. Under this scenario growers will need to consider spot-sprays for these potentially very damaging pests where the PHI of the pesticide is compatible with the harvest dates of the affected cultivars.  Please consider the following:

Orchards that used Assail and/or Belay for first generation codling moth management have experienced minimal impact on WAA predator populations and have had nearly 100% of their WAA colonies were parasitized. However, in some orchards, there is not much bio control and if this is the case, it is likely there could be WAA round the stembowl of the apple at harvest and need to manage this August population as early as possible, since it can explode in September.

Brown marmorated stink bug and native stink bugs
This year BMSB has been rather light across the region, though populations generally do not increase until September.  Mid-August is when we begin seeing more BMSB and mostly nymphs are what has been observed. Dane and Rock County in southern Wisconsin have the most established population of BMSB. Injury has already been observed this season in these orchards, with most being on the edge of the block. Native stink bugs are also very common and more widespread through the state.  The injury from native vs. BMSB is indistinguishable and can be confused with cork spot, bitter pit or even hail.

In collaboration with the Wisconsin Department of Agriculture Trade and Consumer Protection, the IPM Institute monitored brown marmorated stink bug (BMSB) in Wisconsin orchards between 2015 and 2020. The spread and emergence of BMSB have been tracked, starting with pyramid traps in 2015 or 2016 and later improving to a two-lure trap. In 2020 traps were set at 30 locations with additional traps at the University of Wisconsin Madison and at CSA community farms and gardens.

The pest has a strong preference for apples, but the host range for BMSB extends to tomatoes, sweet corn, peppers, green beans, woody perennials and has over 300 suitable hosts in North America.

All growers statewide should monitor BMSB with a trap or visually along the perimeter and interior of the orchard during harvest. Unlike many of the other apple pests, BMSB does not settle down at harvest. Growers should order and set up traps along orchard perimeters or in the front yard. Putting traps in the middle of blocks is not advised. Based on emergence patterns, we can expect to find this pest in higher numbers in our homes and buildings for about a season before they pose a more serious agricultural risk. Be aware of BMSB in your packing sheds and homes in addition to monitoring in the orchard.

Insecticide efficacy and performance varies greatly across and within different chemical classes. Imidan (phosmet) has performed poorly in bioassays and field trials against BMSB. The best performance against BMSB has been from the older synthetic pyrethroids, e.g., Brigade (bifenthrin). The neonicotinoids have limited efficacy but can be used. Actara (thiamethoxam) has performed the best, however, its use is limited by its 35-day pre-harvest interval (PHI). There are two newer neonicotinoids called Venom and Scorpion (dinotefuran) with a shorter PHI, but these have only been registered for apples under emergency registration exemptions out East. If BMSB became a problem, these materials will likely become registered for growers in the Midwest.

In addition to monitoring BMSB with traps, growers should scout within 100 feet of the orchard perimeter. When stink bugs find an orchard, they tend to spend several days to a week in the perimeter before moving into the interior of the orchard block. This results in a strong edge effect. When scouting, growers realistically wonâ€t be able to see incision injury from proboscis injury. This will, however, result in a deep cork spot where juice has been sucked out, whereas other insect damage, bitter pit or bruising will be much shallower. When stink bug feeds on an apple, there are often multiple feeding sites. Find more information on distinguishing bitter pit, apple maggot and BMSB damage in MSUâ€s 2017 article, http://msue.anr.msu.edu/news/look_a_like_late_season_apple_damage.

Another good resource is www.stopbmsb.org. This is a national clearinghouse for all the current research on BMSB.

Black stem borer
Remember to monitor the edges of blocks of young trees for two weeks this month. https://www.canr.msu.edu/news/time_to_start_monitoring_for_black_stem_borer

Fruit size
Most cultivars across region have light to moderate fruit set because of poor return bloom or multiple frost events this spring. Some cultivars may have problems with fruit size, where fruit size is determined by multiple factors, many of which are weather related, from poor pollination to frost damage to heat or water stress during the growing season. In particular, Honeycrisp greatly varies in size and often within the same tree. Some of these small Honeycrisp are now coloring and ripening much earlier than the normal sized fruit on the same trees. Most of the small fruit seem unlikely to achieve market size and while it is tempting to simply attribute these small apples to a lack of water or an excess of heat, evidence from irrigated blocks suggest the fruit were damaged during the spring freezes. Itâ€s also possible the extended bloom that produced this fruit were caused by insufficient chilling hours during late dormancy or from weather stress during last yearâ€s growing season, was causative. It would be helpful if growers could make notes at harvest regarding the fate of these small fruit on the various cultivars affected as that information may help tease out the actual causative factors.

Pre-harvest interval reminder

Pesticides and pre-harvest intervals http://cpg.treefruit.wsu.edu/pesticide-intervals-impacts/preharvest-intervals/

 July 27 Call Stream: CLICK HERE

Regional update

Table 1. Degree days forecasted for 7/27/21 from Cornell NEWA system. Find your local station today: http://newa.cornell.edu. Note: Leaf wetting hours for sooty blotch and flyspeck use an estimated petal fall date, unless entered by the station operator. NEWA model allows you to add your last systemic fungicide or petal fall date.

Foliar and soil sampling
Leaf and soil samples for nutrient analysis should be collected no later than the week of August 17^th from this seasonâ€s growing shoots. The purpose of collecting the samples now is to inform nutrient management for next year. Samples may be sent to AgSource Laboratories (https://www.agsourcelaboratories.com/) or the UW Soil and Forage Lab in Marshfield Wisconsin (https://uwlab.soils.wisc.edu/). The UW lab includes soil and tissue samples for $25. Tissue sample pricing from AgSource Laboratories is dependent on your specific location. Contact your nearest lab for pricing options.

Soil analysis through AgSource includes the following soil-sampling packages:

• Basic Package ($45) – includes: Soil Health Score, CO₂Respiration, C:N Ratio.
• Routine Package ($55) – includes: Soil Health Score, CO₂Respiration, C:N Ratio.
• Complete Package ($65) – includes: Soil Health Score, CO₂Respiration, C:N Ratio

When collecting leaves, examine this yearâ€s growing shoots and select several leaves from the middle of the shoot. Leaves should be collected from a representative sample of the block or variety. About 30 leaves are needed to have one cup of dry leaf material that will be ground up for the analysis. Samples should be separated by variety or by health of the tree. Analysis of unhealthy trees should be kept separate. We are unsure if the results in mixed-variety orchards would be skewed by collecting leaves from multiple cultivars and it is recommended to keep samples limited to specific varieties. Once we see nutrient deficiencies this time of year it may be too late to amend this year and results will be focused toward soil and tree health next year.

Summer Apple Nutrition and Pre-Harvest Stop-Drop Sprays: Recap of Brian Smithâ€s article in WI Fruit News: https://fruit.wisc.edu/2020/07/22/summer-apple-nutrition-and-pre-harvest-stop-drop-sprays/
Dr. Brian Smith references the most important aspect of tree nutrition is having adequate soil moisture and describes this as maintaining soil moisture at 50-70% of field capacity. This is very relevant as all the nutrition points we discuss in AppleTalk are dependent on adequate soil moisture. Not everyone has irrigated trees, but water can be delivered to these trees, even if it is labor intensive, do it.

Field capacity is an old term in soil science and is somewhat vague. The textbook definition refers to field capacity as the amount of moisture soil can hold after excess water, i.e., water the soil cannot hold, has drained away. The field capacity Brian is suggesting we target is a middle range of soil moisture, where there is no free water and not so dry that roots cannot pick up moisture. Even if there is still some water in the soil, if the soil is too dry, roots may begin to die. A foot of soil can hold upwards of two inches of rain that trees can access. The lighter or sandier the soil, the lower the water-holding capacity and as soil-organic matter, silt, or clay content increases, so does the soils water-holding capacity, which could increase above two inches.

The most easily assessed metric for assessing water stress is to use the evapotranspiration (EVT) models available via local NEWA sites. Considering the EVT rates over the last month, a significant amount of water has been removed from the soil. It is worth the investment in soil tensiometers and other tools that will help assess soil moisture. As a reference point, corn growers often discuss needing an inch per week. This is likely a minimum amount for fruit trees and could require more depending on EVT rates. Therefore, if we have not had four inches of rain in July, the trees are likely under significant tree stress.

Questions on soil moisture and fruit drop: Will watering help to stop premature fruit drop?
Yes, frequent watering should help to prevent this early drop. Additionally, fruit low in Mg or high in K or B, are more likely to be at risk of dropping.

Bitter pit
Calcium (Ca) is important and necessary to maintain fruit quality. The majority of Ca is absorbed into the fruit during the cell expansion phase lasting from petal fall to the end of July (~50 days after petal fall). After this period, the xylem in the fruit losses efficiency, especially in the calyx end. Calcium does not easily move into the fruit from the soil and is relatively immobile within the tree. Concentrations can vary between foliage, fruit, and soil.

Note: Foliar Ca levels will be greater than what is in fruit because leaves have a high transpiration rate and accumulate more Ca material. The following factors can influence Ca levels and incidence of bitter pit: Nutrient imbalances with nitrogen (N), potassium (K) and boron (B), soil moisture levels and fruit size.

Strategies for reducing bitter pit

1. Submit foliar, fruit and soil samples for nutrient and pH analysis. It is recommended to test samples for all available macro/micronutrients as many complex interactions exist. For example: an excess amount of magnesium (Mg) or potassium (K) will compete with Ca for uptake.
2. Keep soils adequately hydrated throughout the growing season.
3. Reduce excessive vegetative growth. Reducing vegetative growth will redirect the transport of Ca from foliage to fruit. Apogee (prohexadione calcium) can be applied to curb vegetative growth. The pre-harvest interval for Apogee is 45 days.
4. Lite crops or excessive thinning can result in large fruit. Calcium levels can be diluted in large fruit; Ca concentrations typically vary from stem to calyx end (location where bitter pit symptoms are most pronounced), excessively large fruit usually have exacerbated symptoms.
5. Calcium sprays can begin at petal fall and continue to end of August; up to six applications may be necessary. Coverage is important – Ca must contact fruit to be effective. The recommended rate is one-to-two pounds of Ca per 100 gallons of water. If visible symptoms of bitter pit are present, it is not too late to apply Ca to prevent further injury.

Plant growth regulators
ReTain (AVG-HCl) reduces amount of ethylene produced to prevent the abscission layer from forming between the fruit stem and spur. The general recommendations for use of ReTain on Honeycrisp are to apply a half rate 30 days before harvest. Other recommendations would allow a ¼ rate to be applied within 14 days of harvest or to include NAA, e.g., Fruitone, at 10 PPM with the ¼ or ½ rates. Honeycrisp does not produce a lot of ethylene and therefore is more sensitive to Retain. This means that a “half rate” is essentially a full rate. The use of Retain with NAA can extend harvest another seven to ten days. The combinations can continue to promote ripening and inhibits separation at the abscission zone.

It is not recommended to apply these materials in complicated tank mixes and to also read product label for compatibility statements. When first using these materials experiment with application timing and rates for specific varieties to help determine what works best for your orchard.

Blush (prohydrojasmon) can enhance color development, especially on the backside of the fruit that does not color well. Blush does not accelerate ripening. Some growers prefer to not apply blush to Honeycrisp, so pickers can use visual cues based on harvest parameters.

Insect management
Leafrollers
The first obliquebanded leafrollers (OBLR) of the second-generation flight were observed in the last week, however many locations are still likely waiting on the flight to begin. The second-generation of OBLR will hatch in mid-August and can continue into September. This generation typically feeds on ripening fruit rather than on vegetative tissue. The OBLR larvae will only grow to a few millimeters in length before developing a pupa and going into diapause, where the OBLRâ€s growth and development is suspended until spring.

Redbanded leafrollers have a wider set of host species, fly further, and traps can capture a lot of males. We often times donâ€t see a lot of larvae hatching out in correlation with trap captures. This is not the case with OBLR, as female moths are more commonly captured.

The CM larvicides, e.g., Delegate (spinetoram), Altacor (chlorantraniliprole), will control these larvae, whereas the neonicotinoids, e.g., Assail, Admire Pro (imidacloprid), do not. The application rate for these insecticides is typically the same that is used for codling moth. Imidan (phosmet), had a real ability to become resistant to OBLR. We get little resistance with RBLR because of their wide-host range. Managing the second generation now, will reduce the overwintering population that may need to be controlled next spring. Three to five percent injury is possible at harvest and scouting needs to be used to determine if a treatment is warranted. A mistake with OBLR may discount an apple from US Fancy grade but is not usually a problem when selling pick-your own fruit since the injury is very small and there is no worm in the apple. Two traps per 20 acres is adequate to determine where treating is necessary.

The degree-day model for OBLR is based on a lower developmental threshold, 42-43°F. Using this lower-base threshold will allow degree days to accumulate faster. The important consideration is that no trap threshold exists to help time sprays. Typically sprays for OBLR are applied after large flights. Since OBLR have a narrower-host range and will not fly very far, trap captures are a good reflection of pressure within the orchard. Low captures of five or six OBLR, do not signify a problem. Captures of 15+ should be followed up with a typical spray we use for codling moth.

Michigan State and the Utah IPM program have similar degree-day models for OBLR. Utah suggests the first-generation flight occurs at 1025-1175 DD from January, 1 base 43°F. The flight for the second generation in Utah begins at 1100 and hatch begins at 1500. Michigan suggests that OBLR biofix occurs around 900 DD from January 1 base 43F. The peak moth flight for second generation OBLR will happen at 2300 from the biofix date and egg hatch will start at 2750 DD base 43°F.

The OBLR degree-day model is explained in the following two articles:

• http://www.treefruit.msu.edu/extension/CAT/21_7.pdf
• https://climate.usu.edu/includes/pestFactSheets/Leafrollers-in-Fruit-Orchards.pdf

Mites
European red mites (ERM) and to a lesser extent two-spotted spider mites (TSSM) have continued to be a problem in orchards where predators have not been successful at managing the populations. The threshold for August is 7.5 mites per leaf and while it is relatively easy to count ERM, populations of TSSM can be much more difficult to assess due to their webbing and size and do not have a specific threshold. The predator complex will be more effective with the cooler weather this week. The cooler weather will also allow for applications of oil.

Organic producers do not have many options for mite control, though many oils are OMRI approved. Oils should be applied in cooler temperatures, and most days in July were likely too warm for an application. Some larger growers have had problems with resistance developing to most of the miticides that are commercially available. As a result, one grower has experimented with summer oils this year and used a product called JMS Stylet oil, which is a paraffin based mineral oil. It is approved for organic use and has been in use since the 1960â€s. Nutrien in Galesville, WI does have this product. Apply at a 1-2% rate per acre and John recommends using more water as it will increase the chance that the mite will suffocate. Keep in mind that when using oils, it will also kill predator mites. Oil is considered another mode of action, so a miticide used several years ago and have made several years of oil applications, it is okay to use it again as a spot or cover spray.

If bronzing is still occurring while mite populations are below threshold, action is required to prevent further economic injury to the plant. This happens when a population of predators have remained active long enough to keep populations below threshold, yet enough mite feeding has occurred to cause leaf bronzing. Once leaf bronzing occurs, economic injury is happening to the tree and a miticide should be applied. This scenario is referring to what we call mite days, where the duration of mite activity is just as important as the actual population. If we reach threshold and still cannot see significant damage on any leaves, we may be questioning whether we need to make a miticide application.

Pre-harvest interval reminder

List of pesticides and pre-harvest intervals http://cpg.treefruit.wsu.edu/pesticide-intervals-impacts/preharvest-intervals/

July 20^th Call Stream: CLICK HERE

Table 1. Degree days forecasted for 7/20/21 from Cornell NEWA system. Find your local station today: http://newa.cornell.edu. Note: Leaf wetting hours for sooty blotch and flyspeck use an estimated petal fall date, unless entered by the station operator. NEWA model allows you to add your last systemic fungicide or petal fall date.

Regional roundup
The forecast calls for hot weather, with highs reaching the upper 90s this week and little chances of rain in the forecast.  Under these conditions, diamides and neonicotinoids applied for second generation codling moth or apple maggot could last longer than two weeks if applied at full rates and mixed with a good spreader/sticker/UV protectant, e.g., Attach. Growers are nearing their 250 DD from second generation biofix and apple maggots have been steady for growers with historical pressure. We have accumulated enough RH hours now that all growers should be considering an application of Topsin M to manage summer diseases, even if there has been a lack of rain fall in your area. Blocks with historical pressure from bitter rot could receive a strobilurin application such as Flint (trifloxystrobin), but if bitter rot pressure is low, this can be delayed to August. Organic growers may consider potassium bicarbonate or Regalia for sooty blotch and flyspeck management.

Insects
Codling moth
Most growers should have accumulated enough degree days, that moths flying now would be part of the second generation. However, rather than continuing to count degree days from first generation biofix, it is recommended to reset your degree-day counter and tally degree days from zero. Even though there are 1000-degree days between generations, your second generation biofix is not necessarily going to be at 1000-degree days.  Realistically it could occur anytime between 1,000 and 1,250 DD from first generation biofix. For this reason, only use first generation degree days to differentiate first from second generation moths but reset your degree day counting to zero once you have established a second generation biofix.

During the second-generation flight it can be confusing when one trap captures high counts well over threshold and another trap has captures below threshold. Determining the significance of your second-generation flight can be clarified by totaling all the trap numbers by date and add up by week, e.g., combine trap data for a week.

Spray timing for this generation can use the same population model that is used in first generation. The difference between 250 vs. 350 DD can be significant, as at 250 DD there is only 3% egg hatch versus 15% egg hatch at 350 DD. This larvacide application could still be delayed to 350 where trap counts are low, however, if there was a strong flight with captures significantly over threshold, the larvacide would have to go on at 250. A larvacide applied this week will not provide control of the entire generation, but subsequent treatments should be determined based on additional trap counts.

If your goal is to only apply one larvacide during the second generation, consider this should only be done if you got good first-generation control and are not seeing any injury. There is lots of variability in the timing of when second-generation eggs hatch and the longer the larvicide application is delayed from second-generation biofix, the greater number of moths will be targeted by that application. If you are finding injury, e.g., live worms or just the tunneling, expect to have higher numbers in traps during second generation and plan on multiple larvacide applications.

Apple maggot
Despite dry weather for many, this has not held back apple maggot flights.  During last weekâ€s call we discussed apple maggot management in great detail, please see those notes for additional guidance. The following discussion focuses recent efficacy data using feeding attractants and for use of an OMRI approved insecticide which is showing promising results for apple maggot management.

Organic management options for apple maggot are generally limited mostly including frequent sprays of PyGanic, Kaolin-clay or use of apple maggot trap out with red spheres. Newer biopesticides have been in development and two products growers have expressed interest in are Venerate XC and Grandevo.  Both of these are fermented by products bacteria that are naturally occurring and both products are OMRI certified.  Venerate has been found to perform well at repelling brown marmorated stink bug feeding and in apple maggot acts as a stomach poison, e.g., the flies do need to ingest the product. Both Venerate and Grandevo have also been found to perform well against the crawler stage of San Jose scale.

Testing of Venerate was completed season long and while trials were completed for three consecutive years, this data represents 2017 only. Apple maggot sampling was completed using two methods.  On August 24 one bushel of fruit was randomly harvested and inverted on wire racks to allow apple maggot larvae to emerge from fruit at time of pupation and drop into sand.  The number of larvae that emerged from each bushel were counted. Apple maggot tunneling was evaluated on September 11 where 50 fruit were collected and evaluated for tunneling.

The 2ee label for Venerate recommends two quarts per acre, however the trials were completed using one quart per acre and Marrone Bio did confirm that if applied with adequate water and to all rows, e.g., no alternate-row spraying, growers could use the lower one-quart rate. The performance of Venerate is improved when used with a sticker, Nufilm-P was recommended for Organic growers by Marrone and conventional growers could use one of the products included in the trials (Table 2). Venerate is susceptible to washoff, and Marrone cannot attest to its efficacy if spray intervals are extended or if the product is applied more frequently than 14-day intervals. Lastly it should be noted that Venerate XC has not performed well in trials for second generation codling moth.

Marrone Bio has also trialed Grandevo for apple maggot and while there were some instances of it performing well against AM, they feel the data is too inconsistent to support a recommendation for its use against apple maggot.

• Venerate XC label: https://s3-us-west-1.amazonaws.com/agrian-cg-fs1-production/pdfs/Venerate_XC_Label1p.pdf
• Venerate 2ee label: https://marronebio.com/download/2ee-venerate-xc-for-apple-maggot/

Table. 2017 Jon Wise insecticide efficacy trials at Trevor Nichols Research Station.

There have been several studies in recent years demonstrating that any amount of sugar applied to tank mixes can help improve performance of imidacloprid for managing apple maggot. Apple maggots are are nectar feeders and the sugar is replicating the attractiveness of nectar. Since most insecticides need to be ingested by apple maggot in order have efficacy, adding sugar as a feeding stimulant can help increase uptake of the pesticide.  John recommends one quart/100 gallons of molasses or corn syrup.

San Jose scale (SJS)
The hot weather this year, similar to mites, has been a boon to SJS growth and development, so much that we are concerned about the possibility of a third generation this year. In the meantime, expect to see second-generation crawlers in the next three weeks.

SJS has a degree-day development range from 51°F to 90°F, which means DD will accumulate faster than what we calculate for codling moth. The Washington State University model suggests 1% of second-generation crawlers would emerge after 1200 DD from biofix, which is approximately 275 DD from January 1 and 50% second generation crawler emergence would be complete by 1580 DD from biofix. Essentially, to get an estimate on second generation crawler emergence add 275 DD to the table on the WSU site to calculate DD from January 1. So, if 1% second-generation emergence occurs from biofix, this would be approximately 1475 DD from January 1.  Currently, 1371.75 DD base 51F with upper limit of 91F have accumulated since January 1 at the Verona, WI NEWA station. This means some locations in southern WI are only 100 DD from the start of second generation crawlers. http://treefruit.wsu.edu/crop-protection/opm/san-jose-scale/

The recommended management options include Sivanto or Centaur. If neonicotinoids were applied between petal fall and early July, they should not be used to target this second generation of SJS. Even though Beleaf 50 SG has a label for SJS, FMC has indicated it should not be used against SJS. The FMC technical specialists have observed good efficacy of Exirel on SJS crawlers, however, there is no information published to date to support this and SJS is not currently on the label. Additionally, while SJS in organic orchards is uncommon, it is not unheard of, and organic growers with scale populations can target crawlers with either Grandevo or Venerate XC. All of the above options should be applied with a good spreader/sticker and with lots of water, possibly more than 100 Gal/acre where trees are large and canopies are dense. Double sided stick tape or electrical tape with a layer of petroleum jelly should be set on one and two-year old wood where SJS has been observed this year. Once crawlers are caught, they should be targeted immediately.

Mites and miticides
As expected, European red mites have been basking in the hot weather as they delightfully suck the chlorophyl from our appleâ€s leaves. The abundance of these mites is also countered by very high populations of predatory mites that John and Peter have observed in many orchards. If bronzing is still occurring while mite populations are below threshold, action is required to prevent further economic injury to the plant. This happens when a population of predators have remained active long enough to keep populations below threshold, yet enough mite feeding has occurred to cause leaf bronzing.  Once leaf bronzing occurs, economic injury is happening to the tree and a miticide should be applied.

Mite thresholds have increased from 2.5 to 5 mites per leaf and will increase to seven mites in August.  Some growers have already seen mite captures exceed threshold and growers should be aware that in addition to the wide range in performance of miticides, each orchardâ€s mite populations respond uniquely to a treatment. Mites donâ€t travel between orchards and you own your own mites, which means your mites have been exposed to whatever you have applied year after year in your orchard.

Some miticides work only as an ovicide and larvacide, whereas other miticides offer good contact activity on all motile stages. Where mite populations have exploded, miticides such as Zeal (etoxazole) and Envidor (spirodiclofen) will not offer the level of immediate knockdown of adults that is desired. Miticides with good contact efficacy include Acramite (bifenazate), Kanemite (acequinocyl), Nealta (cyflumetofen) and Portal (fenpyroximate).

Woolly apple maggot
Woolly apple aphids have been observed with increasing abundance across the region and John and Peter are also observing lots of syrphid fly larva, gall midge maggots and mummification from Aphelinus mali the parasitic wasp that exploits WAA.  This excellent bio control is being observed in orchards where Delegate has been avoided for first generation codling moth. If WAA needs managed, options are limited and include Beleaf (21-day PHI) or Closer (7-day PHI).

Disease management
The drought is playing a major role in affecting tree health this year.  Trees without irrigation are at risk of dropping leaves and defoliating, which is a survival mechanism. Prior to leaf drop you can expect to see chlorosis and other necrotic spots. So, this may be one of the diseases, but could also be from drought stress.

White rot
It is not easy to distinguish black rot from white rot, and the difference is identified by the appearance of the rot going into the core of the fruit. John describes most of these lesions as black rot due to it being observed every year via the frog eyed leaf spot in leaf tissue. However, white rot may be even more widespread. Captan prevents fruit infection but does not help prevent infections of the trunk, though is possible that captan on the bark might offer some protection. The white rot invasions that Peter observed likely happened last spring after the polar vortex, and while it seems the cankers appeared out of nowhere, the fungi have been present for a long time. When trees become stressed, the trees stop producing compounds that can help prevent the spread of these infections.

If trees have bark injury from herbicides, rodents, weed whips, etc., these trees are at risk of being infected by canker fungi when there is warm, wet weather. Many larger infected trees can withstand and fight off many of these infections for years, but the margin of error on a high-density planting is very small. Trees can likely be invaded in year one if they are not cared for properly.

Black rot
Black rot infections on fruit usually appear at the calyx end and can originate at any wound that penetrates the epidermis, e.g., insect or hail injury. Black and white rot can be difficult to distinguish and spore producing lesions are black for both types of rot. Usually only one spot occurs per fruit, a characteristic that distinguishes black rot from bitter rot. Initial infection becomes brown and stays brown or turns black as it increases in size. A series of concentric rings often forms as the rotten area increases in size and lesions are usually amorphous. The flesh of the decayed area remains firm and leathery, and fruiting bodies will appear on the surface of the rotted tissue.

Fungicides that protect against fruit rots include captan, strobilurins, e.g., Pristine (boscalid, pyraclostrobin) and Flint (trifloxystrobin). Do not apply strobilurins if scab lesions are present. A high rate of captan may provide adequate protection. Note: To reduce resistance concerns always tank mix single-site fungicides with a protectant.

 Leaf damage
In mid to late summer, leaf injury from a variety of causes becomes more visible.  When assessing this injury, it is important to look at the entire shoot and leaf cluster.  Most leaf injury in the form of brown or necrotic spots are present on mature leaves and looks older.  This injury appears as brown spots or burnt necrotic areas of various circular sizes.  Many growers have been reporting small specks and wondering if these symptoms could be a more serious problem.  Many symptoms are the result of black rot infections.  Frogeye leaf spot is a dead-end of the black rot disease life cycle, where alternaria leaf blotch does continue to spread.

Growers need to look at the entirety of the damaged leaf.  If injury is surrounding fruit clusters but all new growth and terminals are not affected, it is unlikely to be from these fungi.  If infections are occurring at the ends of the terminals and on new growth, then this could be related to black rot, frogeye leaf spot or alternaria leaf blotch.  Older leaves could also have damage caused by several chemicals, e.g., oil, Flint (trifloxystrobin) or captan.  Orchard floor hygiene is important when managing overwintering inoculum, including these fungi.

Frogeye leafspot
Symptoms are defined by their purple to red margins around the leaf surface with a brown middle. Lesions appear several weeks after petal fall and will grow to 3-6 mm in diameter. Frogeye leaf spot can be confused with phytotoxicity from pesticide application, use the purple margins as defining characteristics of this disease. Once present on the leaf surface, this disease will not release spores or cause additional infections.

Alternaria leaf blotch
Symptoms appear as brown blotches that are 2-10mm in diameter on leaves and are surrounded by a dark margin. The leaves turn yellow over time and will die prematurely. Fruit appear sunken with small (~2mm) brown spots surrounded by a black border. Alternaria leaf blotch usually affects high value cultivars like Royal Gala, Fuji, Pink Lady and Red Delicious.

Marssonina leaf blotch
Marssonina leaf blotch is a foliar disease with a similar life cycle to apple scab. It overwinters as a fungal spore in leaf litter on the orchard floor. Contrary to apple scab, it is a warm weather disease with infection periods occurring in mid to late summer. A definitive sign is early leaf drop occurring in August and early September. Some cultivars are more susceptible than others.

Fruit sunburn
Fruit sunburn has been increasing over the last several seasons, especially as adoption of high-density plantings increase. Sunburn can occur as early as mid-July and is still a threat through early September. Anecdotal evidence suggests that fruit becomes more susceptible to heat and sunburn injury increases near harvest. Damaged flesh is vulnerable to colonization by various fruit rots, requiring fungicide programs to be modified if symptoms of rot are detected. Sunburned fruit is also susceptible to changes in pigment, restricted coloring, and degradation of internal-fruit quality.

• Sunburn occurs when shaded air temperatures are above 86°F and fruit temperatures are above 113°F
• Sunburn necrosis is caused by heat and when fruit-surface temperatures reach 126°F for 10 minutes.
• Sunburn browning is the most common form and results in yellow, brown, or dark tan patch on the sun-exposed side. Threshold is 115 – 120°F for one hour. Cells are not killed, even though the skin loses color.
• Photo-oxidative sunburn (bleaching) occurs when shaded or partially shaded apples are moved into strong or direct sunlight, e.g., most often occurs when weight of a heavy crop load moves branches and exposes previously shaded fruit to the sunlight.
• Sunburn bleaching is independent of temperature and is caused by visible light.

Additional environmental factors that may result in sunburn include intensity of solar radiation, cloud cover, humidity, wind, and growing conditions including canopy density, variety, fruit size and water stress. Higher humidity reduces the occurrence of fruit sunburn, while fluctuating temperatures increases the occurrence of fruit sunburn. Sunburn damage can cause fruit to be more susceptible to summer fruit rots, e.g., bitter rot. Varieties at greatest risk of sunburn include Braeburn, Fuji, Honeycrisp, Jonagold, Gala, Ginger Gold, Golden Supreme, Granny Smith, Royal and Zestar.

The impacts of fruit sunburn can be mitigated by scheduling frequent irrigation to avoid tree-water stress; avoiding excessive summer pruning, especially before or during hot weather; protecting picked fruit in bins from direct sunlight and keeping fruit cool by improving orchard airflow. It may not be necessary to apply a sunburn material if paying attention to fruit rots.

There are three primary types of protectants that can be applied directly to the fruit to mitigate sunburn. Generally, these all work under the principle of reflecting ultraviolet and infrared radiation which can damage the fruit skin or cause overheating. These include:

• Clay based: kaolin clay, e.g., Surround WP.
• Calcium carbonate-based: Purshade (62.5% calcium carbonate). Growers that have used Purshade do not usually apply after end of July because it is difficult to wash off harvested fruit.
• Wax based: Raynox (water, carnauba wax, organically modified clay, emulsifiers). Growers have noted that it is difficult to mix in the spray tank and there can be issues with the materials clogging nozzles. For more information visit: Raynox Plus applications to prevent sunburn of Honeycrisp apples, Jon Clements, Sunday, December 6, 2015, http://jmcextman.blogspot.com/2015/12/raynox-plus-applications-to-prevent.html

Additional resources

• Sun Protection for Fruit, A practical manual for preventing sunburn on fruit – 2011, Department of Primary Industries, Farm Services Victoria Division: http://mvcitrus.org.au/mvcb/wp-content/uploads/sites/343/2012/09/Sun-Protection-Manual-for-Fruit.pdf
• Which Type of Apple Sunburn is in Your Orchard?, Washington State University – Decision Aid System, June 1, 2020: https://decisionaid.systems/articles/Which_Type_of_Apple_Sunburn_is_in_Your_Orchard
• Sunburn of Apple Fruit: Historical Background, Recent Advances and Future Perspectives: https://www.researchgate.net/publication/263416395_Sunburn_of_Apple_Fruit_Historical_Background_Recent_Advances_and_Future_Perspectives

July 13^th Call Stream: CLICK HERE

Table 1. Degree days and ascospore maturity downloaded on 7/12/21 from Cornell NEWA system. Relative Humidity hours added on 7/14/21. Find your local station today: http://newa.cornell.edu. Note: Leaf wetting hours for sooty blotch and flyspeck use an estimated petal fall date, unless entered by the station operator. NEWA model allows you to add your last systemic fungicide or petal fall date.

Regional roundup
After a period of significant rain fall for most growers, we now enter a week of dry and sunny weather with highs in the mid-80s and lows in the upper 60s. There are no forecasted highs in the 90s over the next ten days.  After an excessively hot June and early July, the next ten days look pretty good for working in the orchards.

This weekâ€s notes bring a special focus on codling moth, apple maggot and summer disease management.  Please see our June 29^th notes to review monitoring and management recommendations for Japanese beetle, woolly apple aphid and other secondary pests.

Disease management
Sooty blotch and flyspeck
Acknowledgements
An important objective of AppleTalk is to keep us all informed when new advances in the science require us to recalibrate our decision-making processes. Management of sooty blotch and flyspeck (SBFS) is one of these situations.  There have been several important studies over the last 25 years and in the last ten, more work has been done to validate a SBFS model that uses accumulation of relative humidity hours vs. leaf wetting periods. The following summary outlines the evolution of this model and includes information I obtained through recently published papers and conversations with Dr. Dan Cooley, UMass, who developed the model used by NEWA and Dr. Mark Gleason, who developed our preferred model using relative humidity and emails correspondence with Juliet Carol and Dan Olmstead, Cornell, who manage the NEWA network and explain the nuances of how NEWA is calculating wetting events, etc. The conclusions summarized at the end explain how to use relative humidity hours to time SBFS sprays and will be the preferred recommendation in AppleTalk going forward.

The application of the sooty blotch and flyspeck model is a classic example of how we can elevate our use of predictive models in an IPM system to minimize preventative fungicide sprays, when compared to calendar-based programs. However, confusion emerges as we examine the various ways this model has been validated and implemented across the eastern United States. The biggest point of contention being how wetting periods are tracked; the technology used to monitor them; and the thresholds used to time the spray. The model used in NEWA has a threshold of 175 leaf-wetting hours (LWH) and counts all hours. However, this is contradictory to other Extension publications which use the same threshold, but discount all wetting periods less than four hours.  Additionally, I have read that all hours can be counted, but a threshold of 200 – 270 LWH should be employed. After inquiring with the pathologists who helped write the NEWA model, it has been clarified this model is a modification of the original Brown and Sutton model, which only counted leaf-wetting periods > 4 hours, however, had a threshold of 200 – 250 beginning with the first rain 10-days after petal fall. But Brown & Sutton used a DeWit LW meter to develop their model, and it used a string that would tighten or loosen as it dried or became wet; even the authors acknowledged it might not work with electronic sensors.

Hartman and Smigell tested the model using electronic sensors and found the DeWit required more wet hours than the electronic sensor. Further testing was completed in Kentucky, where the treatment threshold was adjusted to work with an electronic leaf-wetness sensor. They adapted a technique first used to study SBFS, wherein fruit are covered by bags for varying periods during the season to determine when fruit were first infected by SBFS. At regular time intervals of approximately 1 week, fruit were arbitrarily bagged. Fruit bagged before 175 LWH measured from 10-days after petal fall did not develop SBFS. Based on this, the researchers recommended a 175-LWH treatment threshold counting all leaf-wetness hours. Under this revised model, two to four fungicide applications were saved relative to calendar- based prophylactic sprays.”

However, none of these approaches are a good fit for our climate conditions in the upper Midwest where high levels of relative humidity remain the primary driver for sooty blotch and flyspeck infections. The 2021 growing season is providing us the perfect opportunity to examine why relative humidity is a better predictor of SBFS over LWH.  Ten or so years ago Mark Gleason and Patty McManus validated a model where 192 hours of RH above 97% was a better predictor than 175 hours of leaf wetness for our region. However, NEWA stations record hours of relative humidity equal to or greater than 90%, not 97% RH.  It has been mentioned by pathologists these instruments may not reliably track very high RH levels and is why the NEWA stations are set to measure 90% or greater RH.  A new study published by Gleason et al. in 2017 offers us the best approach moving forward for determining when to apply fungicides for SBFS. This model uses all relative humidity hours from first cover, which is approximately ten days after petal fall and has a threshold of 385 RH hours equal to or greater than 90%. These data may be accessed by going to the ‘Daily Summary†page under the ‘Weather Data†tab on the NEWA website.  You will have to manually tally the RH hours from your first cover spray to accurately determine if you are above the 385 RH threshold. If you examine the tables at the top of this weekâ€s notes you can see the incredible differences between RH and LWHs. At this point, nearly all locations will have accumulated enough RH hours to trigger a SBFS spray.

Unlike other disease models which are preventing infections from happening, the SBFS models simply predicts symptom appearance. A fungicide such as Topsin M (thiophanate methyl), that can eradicate the pathogen must be applied, otherwise symptoms will still appear. NEWA stations located at airports do not often have a leaf-wetness sensor but can still give us RH data for our calculations. It is also note worthy that NEWA stations will calculate one minute of leaf-wetting as one hour, which may be helpful next year when we revisit apple scab management and LWH used to calculate scab infections.

References:

• Hafizi Rosli, Derrick A. Mayfield, Jean C. Batzer, Philip M. Dixon, Wendong Zhang, and Mark L. Gleason. 2017. Evaluating the Performance of a Relative Humidity-Based Warning System for Sooty Blotch and Flyspeck in Iowa, 2017. Plant Disease 101:10, 1721-1728
• Hartman, J. R. 1995. Evaluation of fungicide timing for sooty blotch and flyspeck control, 1994. Fungic. Nematicide Tests 50:10.
• Smigell, C. G., and Hartman, J. R. 1997. Evaluation of fungicide timing for sooty blotch and flyspeck control, 1996. Fungic. Nematicide Tests 52:31.
• Smigell, C. G., and Hartman, J. R. 1998. Evaluation of multi-layer fruit bags for cork spot, sooty blotch and flyspeck control, 1997. Biol. Cult. Tests 13:39.

When do we start protecting against fruit rots?
Initially John thought due to our dry spring, we would have less issues with fruit rots, but now finding that historical data is showing the hot and dry conditions can be a driver of sun induced bitter rot infections and lenticel infections. Zestar always seems to be a good canary in the coal mine for looking for fruit with dark spots/potential fruit rots. John is seeing some fruit that are already showing some signs of sunburn.  The most damaged area may be quite small and nice and round and not necessarily where the apple has shown color because the apple was aligned in a different position when infrared rays were doing damage.  Captan maintained on fruit would help protect against fruit rot.  Considering how light the crop is, growers should hold off on more expensive bitter rot fungicides until later in August. Bitter rot management will be discussed during the next call.

Insect management
Second generation codling moth
The first flight of the second codling generation was documented late last week and last week John thought the flights immediately after the 4^th of July seemed early for a second gen flight but are in alignment with DD accumulations.  At this time, all pheromone lures and trap liners should be replaced. Rather than continuing to count degree days from our first biofix, it would be easier to set a new biofix and count degree days the same way as first generation. Orchards with a strong biofix should not delay the first larvacide to 350 DD, as we often do during first generation.  During this second generation larvicides should be timed at 250 DD and then reapplied after wash-off or the lifespan of the insecticide.  The preferred larvicides for second generation management would include Altacor, Exirel, Delegate.  Combined apple maggot management can be achieved by using Assail. Organic growers may use the codling moth virus, Bt products or Entrust, in combination with mating disruption.

Codling moth and potential for a 3^rd generation?
It is possible that our early accumulation of degree days could be enough to trigger a 3^rd generation that is unable to complete its lifecycle. Larry gut, MSU codling moth and mating disruption researcher, determined if there is enough DD accumulation in May and June, CM larvae in the fruit may be exposed to long photo periods around June 21^st and the subsequent eggs they lay will not pause in their development and move immediately into a third generation. This is a not well understood phenomenon and we are only speculating if this will happen.  Essentially, John suspects the early CM activity could have resulted in 5^th instar larvae being exposed to long photoperiods around the solstice.  Normally these late instar larvae are present after the solstice.  Fifth instar larva would be the biggest worm in the apple and is constantly pushing out frass or when it leaves fruit to pupate. The question we can speculate on is that during the solstice did we have any 5^th instar worms?

If by harvest you are still capturing codling moth it is critical to evaluate the degree day totals and determine if those moths are still second generation or if there is a potential for them to be third.  If based on degree-day accumulations, they are still second-generation moths, then you may continue using the same larvicides as you did during second generation.  If you suspect a third generation then using a different mode of action is essential.  The codling moth virus sold as Madex HP or Virosoft has a zero-day pre-harvest interval and may be a good option for some. Note: The label only allows two Altacor applications per year at the 4.5 oz. rate; Delegate allows four applications at the 7 oz. rate and Assail allows four applications at the 8 oz. rate.

Codling moth resistance management
Earlier this year John had recommended using neonicotinoids, i.e., Belay (clothianidin) and Assail (acetamiprid) to manage 1^st gen CM, in orchards not using mating disruption. This would also offer simultaneous management of secondary pests such as potato leafhopper and green apple aphids. Additionally, late plum curculio would also be suppressed by these neonicotinoid applications.

Orchards that followed this strategy should also evaluate second generation codling moth trap data for signs that may indicate neonicotinoid resistance. Early development of resistance in the codling moth population may not result in enough damage at harvest to suspect resistance. However, codling moth trap captures during second generation that are significantly higher than first generation may indicate the development of resistance, or at the very least, a spray was missed or poorly timed during first generation.

Apple maggot
Growers continue to report early, and high apple maggot captures across the region, with one location reporting more than twenty in one trap.  Consider hanging at least three traps per ten acres and more in blocks with a history of apple maggot injury or where there is pressure from wild apple trees outside the orchard. Organic growers interested in trap out should hang as many traps as they can stand! Officially, Michigan state recommends upwards of 400 traps per acre.  These do not need to be hung all at once but should be fully deployed before the peak apple maggot activity in your orchard.

Neonicotinoids are the primary organophosphate alternative for AM management. Assail (acetamiprid) is often a popular choice because it may be used for both AM and second-generation CM. Recent conversations with Peter Jentsch, research entomologist at the Hudson Valley Fruit lab in New York, suggest that Assail (acetamiprid) is the best apple maggot insecticide option, even over a product like Imidan (phosmet).  His trial data suggests that imidacloprid products perform poorly, though we have not observed that in the Midwest. Field trials with Assail show performance that is equal to what may be achieved with organophosphates.  This performance hinges on the curative properties of the neonicotinoids as a larvacide or ovicide. The neonicotinoids have also been found to repel the adult flies and prevent egg laying. The downside to using Assail has been poor management of the summer generations of leafrollers. Subsequently the use of generic imidacloprid products, e.g., Admire Pro, Wrangler, Montana, in a tank mix with a spinosad or diamide insecticide, has been quite popular. This tank mix results in a reduced risk, yet broad spectrum spray which can manage AM, CM, and summer leafrollers, e.g., obliquebanded and redbanded leafrollers.

Even though we have been successfully managing AM this way, imidacloprid and most of the neonicotinoids do not offer extended-contact knockdown of the female AM fly. Assail does have more mortality on the adult fly and wears off quickly. The main control from Assail and imidacloprid is in the egg laying as an ovicide and survivability of the eggs, and as a repellant. Overall, we have found this strategy to perform well and are yet to hear about AM failures from using the neonicotinoids. However, this does make it hard to spot spray for AM.

Tuesday, June 29^th, 2021, 8:00 – 9:00 AM

Presenter: John Aue, Threshold IPM, jgaue@mwt.net

Moderator: Peter Werts, IPM Institute of North America; questions or comments, pwerts@ipminstitute.org

 

June 29^th Call Stream: CLICK HERE

Table 1. Degree days and ascospore maturity downloaded on 6/22/21 from Cornell NEWA system. Find your local station today: http://newa.cornell.edu. Note: Leaf wetting hours for sooty blotch and flyspeck use an estimated petal fall date, unless entered by the station operator. NEWA model allows you to add your last systemic fungicide or petal fall date.

Regional roundup

As we move into the 4^th of July weekend, we sit in a holding pattern as first-generation codling moth wind down, and accumulation of leaf wetting hours for summer disease management ramp up. Growers should be setting apple maggot traps and refreshing codling moth pheromones. The active weather pattern has offered short-term relief for many, though sub soils are unlikely to have been adequately replenished.

Disease management

Sooty blotch and flyspeck

Captan and Topsin (thiophanate-methyl) are the primary fungicides used to manage SBFS, especially where scab if scab is present. Where secondary scab is not a concern, the SDHI, Strobilurin and DMI fungicides may be used for SBFS. These are attractive because of their ability to also manage black rot and bitter rot. If the first application of Topsin or a single-site fungicide will eradicate the infection when made after the accumulation of 175 leaf-wetting hours from petal fall.  A second application may be made using only captan to protect against future infections, this will allow growers to minimize the use of successive applications of single-site fungicides. The reapplication interval following the first application is dependent on rainfall and weathering of the material. A 2-3 lb. rate of captan is greatly reduced after two inches of rain or 21 days, higher rates may offer added protection. The potential for SBFS to develop resistance to single-site fungicides is minimal because new spores are coming in from outside the orchard and disease is a complex of more than 70 different pathogens. If apple scab is present, it is essential to avoid exposing these single-site fungicides to secondary scab populations.

Research completed on SBFS in the upper Midwest found that relative humidity (RH) rather than leaf wetness hours (LWH), is a better predictor of SBFS infections. It was found that 192 hours of RH above 97% was a better predictor than 175 hours of leaf wetness for our region. During the summer, dew usually contributes to more wetting hours than rainfall. Within the tree canopy, RH is more stable. Since we do not have instruments to gather RH at 97%, it is still recommended to use LWH. It is important to place the leaf wetness plates within the canopy to accurately record LWH. Remember to track RH and the NEWA station to assess whether the readings may be off.

John has observed a number of brambles around orchard perimeters and a few instances of brambles growing within the orchard around the base of older trees. The brambles include blackberries, raspberries or other Ribes species. This is where the pathogen overwinters and is where sexual development occurs. The chance of resistance to summer diseases to Topsin (thiophanate-methyl) or Incognito (thiophanate-methyl) is relatively small which is why we have been able to use these products for decades. It may be worthwhile to remove any of these species where SBFS may overwinter.

Several years ago, our now retired fruit crop plant pathologist, Dr. Patty McManus authored an article highlighting the modern approach to SBFS management using the NEWA stations: https://fruit.wisc.edu/2019/07/05/apple-sooty-blotch-and-flyspeck/

Obliquebanded leafrollers

The first of two summer generations of OBLR are hatching and have been observed across the region at varying growth stages or instars.  Unlike codling moth where it is important to use the maximum rate of an insecticide, lower rates of our normal codling moth insecticides may be used. The neonicotinoids are generally poor at managing OBLR.  If Avaunt, Bacillus thuringensis or an insect growth regulator such as Intrepid or Esteem was used to manage these before petal fall, an insecticide with a different mode of action should be used now. This generation will mostly feed on the terminals of trees, and non-bearing trees are particularly susceptible.  Some fruit injury may occur now, but a majority would occur during the second summer generation in late August.  Managing OBLR now will minimize pressure later in the summer.  If you had a bump in codling moth a week ago, then using lower rates of codling moth insecticides to target OBLR is not advised.

Apple maggot

This week several growers located in southern WI and SE Minnesota sent me photos of their first apple maggot trap captures.  I have come to see a very widespread in the emergence of apple maggot in our region.  Meaning, one of the growers who sent me the photo, always seems to capture AM early, whereas other growers still may not capture their first fly until the end of July.  Either way, the insects can always surprise us, and it is a good idea to get those traps hung, if not already. The last decade many growers have been moving away from Imidan (phosmet) and other organophosphates to manage AM. Avaunt (indoxacarb) was one product that growers tried five or more years ago and have found this to not perform very well. This has left us with neonicotinoids as the primary organophosphate alternative for AM management. Assail is often a popular choice because it may be used for both AM and second-generation CM. The downside has been poor management of the summer generations of leafrollers. Subsequently the use of generic imidacloprid products, e.g., Admire Pro, Wrangler, Montana, in a tank mix with a spinosad or diamide insecticide, has been quite popular. This tank mix results in a reduced risk, yet broad spectrum spray which can manage AM, CM, and summer leafrollers, e.g., obliquebanded and redbanded leafrollers.

Even though we have been successfully managing AM this way, imidacloprid and most of the neonicotinoids do not offer extended-contact knockdown of the female AM fly. Assail does have more mortality on the adult fly and wears off quickly. The main control from Assail and imidacloprid is in the egg laying as an ovicide and survivability of the eggs, and as a repellant. Overall, we have found this strategy to perform well and are yet to hear about AM failures from using the neonicotinoids. However, this does make it hard to spot spray for AM. Historically, we used to be able to just apply tanks of insecticide in the sections of the orchards that had captures or employ strategies like alternate-row middle sprays. Due to how these insecticides perform, complete block or orchard sprays are recommended. When it comes time to apply the final AM spray of the season, an insecticide that is going to kill the adults, e.g., Exirel at high rate or Assail to a lesser degree, are needed, rather than something that impacts egg laying or egg survival.

There is not anything new regarding the timing of AM sprays. If we are relying on baited or unbaited spheres, the narrative suggests that if catching maggot flies on red spheres, they are laying eggs and there is no safe interval to wait to spray. The threshold developed by Cornell is an average of one fly per sphere, where three unbaited spheres are used per ten acres. When using a baited trap, this threshold increases to an average of five flies per sphere.

There is no standard rate for how many apple maggot spheres should be used. Where yellow-sticky boards are used, it is important to remember they only last two weeks. When these sticky boards catch apple maggot, no action is needed. The current threshold from Cornell uses three traps per ten acres. If we increase the density, e.g., one trap per two to five acres, it will better improve our ability to identify where they are coming in from outside sources or identify edges that are hot spots. Orchards with lots of woods along their edge would benefit from a higher density. Keeping this high density along wood lines is beneficial because we cannot anticipate changes in wild hosts in the woods. Even if woods are some distances away, they can fly a pretty good distance. Baited spheres are not going to offer maximum utility until trees have received hail or where we have early varieties, e.g., summer apples, that produce an in-house population that are there year to year. Monitoring these trees separately from the rest of the orchard is important. Unbaited traps work well for most of the season and as we get closer to harvest, growers can consider using baited spheres.

Japanese beetle

The first Japanese beetle (JPB) have been observed throughout the region. Reduced risk insecticide options for JPB are limited, with the neonicotinoids being the most effective option. They are mostly effective as a repellant and anti-feedant, e.g., generic imidacloprid, Assail (acetamiprid). It is important to put out an application before large populations form. Most of these products will also provide protection against apple maggot, potato leafhoppers and aphids. If a product like Assail is used towards the end of July, this would manage second generation codling moth, too. Though it can be effective, growers should avoid using carbaryl products.

Organic and IPM growers also have the option of using neem products (azadirachtin). There are several different formulated products, in addition to using raw neem oil. Neemix and Aza-direct are two formulated products. Most labels do not talk about the ability to act as a repellant, but even though it will not kill adults, neem oil does repel Japanese beetle from immigrating into the orchard. Organic growers wanting to use a raw-neem oil with an emulsifier should check with their certifier to ensure the emulsifier is OMRI-approved. When using a formulated-neem product, the OMRI certificate can be downloaded and generally should be kept with the spray records. Do not apply neem oil during the heat of the day and apply in the evening or nighttime. There is also a Bacillus thuringensis product called BeetleGone, which is quite expensive but should be applied as a spot spray rather than a full orchard application.

JPB females do not like to lay eggs in grass over three inches long and grass that is kept a bit longer may help prevent some egg laying within the orchard. Therefore, close mowing of the alleyways should be avoided when Japanese beetles are active in the orchard. Japanese beetle has a strong preference towards Honeycrisp. If populations are widely dispersed, it is advised to treat the entire orchard rather than making a targeted spray to the heavily infested blocks.

Mites

Mite populations have begun to increase over the last few weeks.  This should be expected partly due to the hot dry weather we have been experiencing over the last six weeks, but also because of the difficultly many growers had in applying dormant oil sprays this spring. Managing mites in August is never the goal and now is an important time to determine where populations exist. Sampling now will set a baseline for future population assessments. The hotter it gets, the faster mites eat, reproduce and eggs hatch. Many insects overwintered well and often we see first spider mite populations going over threshold after petal fall. This has not been observed yet and is not a guarantee they will not hit threshold. There may be more predators out there controlling population numbers. At this stage, rather than using a general leaf count to assess numbers, look at older leaves in problem areas like we do earlier in the spring. Using a 10x hand lens, look at the underside of leaves for mite eggs and assess about half a dozen leaves per tree.

Mite thresholds will increase from 2.5 to 5 mites per leaf in July and will increase to seven mites in August. Some growers are just beginning to see mites emerge and in addition to the wide range in performance of miticides, each orchardâ€s mite populations respond uniquely to a treatment. Mites do not travel between orchards, and you own your own mites, which means your mites have been exposed to whatever you have applied year after year in your orchard.

Some miticides work only as an ovicide and larvicide, whereas other miticides offer good contact activity on all motile stages. Where mite populations have exploded, miticides such as Zeal (etoxazole) and Envidor (spirodiclofen) will not offer the level of immediate knockdown of adults that is desired. Miticides with good contact efficacy include Acramite (bifenazate), Kanemite (acequinocyl), Nealta (cyflumetofen) and Portal (fenpyroximate).

If bronzing is still occurring while mite populations are below threshold, action is required to prevent further economic injury to the plant. This happens when a population of predators have remained active long enough to keep populations below threshold, yet enough mite feeding has occurred to cause leaf bronzing. Once leaf bronzing occurs, economic injury is happening to the tree and a miticide should be applied. This scenario is referring to what we call mite days, where the duration of mite activity is just as important as the actual population. This year may be an interesting one regarding mite days, since we have not had mite populations early on. If we reach threshold and still cannot see significant damage on any leaves, we may be questioning whether we need to make a miticide application.

Apple rust mites (ARM) have often been viewed as food for predatory mites, however, in high-density plantings and non-bearing trees, we are beginning to see more issues with ARM. The ARM will inhibit shoot growth on young trees and populations that appear while the trees are still pushing growth may need to be managed. Terminals are set on most trees and most non-bearing trees; however, some locations are still actively growing. This year we are beginning to see some damage from growing rust mite populations on terminals. Injured terminals will not recover and may not make it through the winter. This does not set the young trees up for a healthy fall and winter, if heavily damaged with rust mites or leaf hoppers. ARM is much less of a concern in mature trees or semi-dwarf orchards.

Envidor works well on rust mites but does not work on two spotted spider mites or European red mites. If these other mite species are a concern, other options are available that will manage all three. Make sure to read the labels, some newer products such as Nealta, do not control apple rust mites.

Woolly apple aphid

WAA populations have been very low this summer though observations of occasional colonies have been more widespread. If you see a white tuft at a shoot and there is only one aphid, it is most likely a single-adult female, even though they look bigger with their “fur coat”. Do not get too concerned at the first sign of the little-white tufts. The colonies are forming relatively late and may have a good opportunity for biological control. Each grower should respond differently to an increasing WAA population based on historic pressure and scouting for biocontrol species, such as, parasitic wasp (Aphelinus mali), syrphid fly larvae and generalist predators that can affect WAA colony growth.

The insecticides Movento (spirotetramat) and/or Beleaf 50 SG (flonicamid), remain the best options to manage WAA, yet need to be applied at petal fall or first cover to offer optimum performance. If these applications were not made, assessing WAA pressure now is critical. If areal colonies are observed and remain small and isolated and you still have growing terminals on trees, an application of Beleaf 50 SG may offer some efficacy or slow down population growth enough to allow beneficial insects to keep populations low later in the summer. Both Beleaf 50 SG and Movento are sequestered into the tree through young and succulent growth. Once terminal buds are set and shoots stop growing, it is less likely for these two insecticides to offer their desired level of management.

Closer (sulfoxaflor) may perform better than neonicotinoids since it belongs to a newer subclass of insecticides that have not been widely used. Do not apply a sticker-type adjuvant, e.g., NuFilm, with insecticides for WAA since the insecticide needs to penetrate the white-waxy coating of the colonies to be effective. Azadirachtin, e.g., Neem oil are probably the best option for organic producers.

Weed management

The most critical time for weed management is in the spring and through early July, during the period of shoot elongation. High density orchards and non-bearing trees are going to be very sensitive to water stress and any weeds in the tree row will also be competing for these water resources, even after shoot elongation ends. For this reason and to reduce risk of rodent injury in the winter, it is beneficial to keep up on weed management through the summer.

If the weeds have got away from you and are now possible 16 – 18” tall or greater, you are going to have a hard time getting good control of these with herbicide sprays. When weeds get this tall, often the herbicide boom push over the weeds, resulting in poor spray coverage and less than desirable results. Therefore, mowing or weed-whacking overgrown weeds and then applying an herbicide after some regrowth, will likely offer better results. For organic growers and those not using herbicides, maintaining close mowing under the trees will continue to help trees outcompete the weeds for water and nutrition resources.

 June 22^nd Call Stream: CLICK HERE

Table 1. Degree days and ascospore maturity downloaded on 6/22/21 from Cornell NEWA system. Find your local station today: http://newa.cornell.edu.

Regional roundup
This next week returns to cooler temperatures with highs in the 70s and low 80s, and cool evening temperatures in the low 60s.  If we are lucky, temperatures in the 90s will not return until the beginning of July. There are several more chances of afternoon thunderstorms later this week, however it should not be too humid.

Horticultural Issues
NAA and return bloom
Ethephon and NAA can be used to promote return bloom in all varieties but are particularly helpful in biannual varieties, like Honeycrisp. There has been more emphasis on using NAA than Ethephon as it seems to perform better for promoting return bloom in Honeycrisp. The flower bud formation for the next year can begin as early as petal fall in Honeycrisp. Any NAA that is applied at petal fall or on 10mm for thinning are also helping with bud formation for next season.

Michigan State recommends three applications of NAA that are applied at five, seven and nine weeks after bloom. Most growers are just now at the five-week mark from bloom and may begin making those sprays. The label recommends rates between 3-5PPM and to begin at five or six weeks after bloom with two additional applications made on seven to ten-day intervals.  NAA may be applied as a tank mix or alone. Some extension articles do recommend leaving out a surfactant or adjuvant if applied as a tank mix. If using a surfactant, reduce to 2.5ppm, though typically it is recommended to use 5ppm and leave out adjuvants and surfactants.

Resources:

• https://fruit.wisc.edu/2019/06/20/return-bloom/
• https://www.canr.msu.edu/news/use_summer_naa_to_enhance_return_bloom_on_apple_varieties

Water management
Please review the rainfall totals at the end of these notes. The duration of the rains compared against totals can also reflect intensity of the storm and likelihood of absorption vs. risk of rain running off.

The accuracy of rainfall totals is dependent on proper rain gauge function.  If you have a NEWA station, it would be beneficial to have a secondary rain gauge where you can compare totals. Orchards to the north of Red Wing MN did not receive any rainfall and orchards near Chippewa falls, WI only received rain during the second storm. Orchards in NE Illinois and SE Wisconsin received very little rain. Only a handful of orchards received a significant amount of rain. It is essential to continue with watering programs, even if you received rain this past weekend. For example, orchards in Richland County, WI lost 4.65” of water through evapotranspiration in June but have only received two inches of rain. Therefore, these orchards are still running a water deficit.  Evapotranspiration rates in Wisconsin can be monitored here: https://agweather.cals.wisc.edu/sun_water/et_wimn.

Disease management
Last week John was calling for reduced rates of captan due to phytotoxicity risk associated with open stomates on apples. Now that it is cooler, reapplication of captan at higher rates would be fine. This may be a benefit to orchards that received hail or wind damage, where tree wounds could open up to canker fungi, and will provide protection against apple scab as we move through an active weather cycle over the next week.

Fire blight
There was a limited amount of hail during the recent storms, with reports coming from western Wisconsin and southeastern Minnesota. If tree or fruit damage occurred from hail or high winds, there is an increased risk of fire blight and black rot creating infections from this trauma. Orchards with a light crop are still susceptible to trauma due to the increased amount of vegetative growth this year. Trees with recent storm trauma and that had fire blight in the past could receive a streptomycin application or a copper application (Cueva). Streptomycin must be applied within 24 hours and some research suggests even sooner. If fire blight appears in young trees, the best option going forward would be to 1. Remove infect limbs by cutting 12 – 24” below the lowest part of the limb showing fire blight symptoms; 2. Apply a growth regulator like Apogee at a high rate (Only beneficial if terminals are still growing); and 3. Apply a copper product, especially if fruit finish is not a concern. Many terminals are already set as a result of the drought and heat we have been experiencing.  If the shoots are no longer growing, fire blight bacteria will not spread as easily, however, open wounds can still receive bacteria and become infected.

Summer diseases
The recent rains brought much needed moisture for our trees but did not drive accumulation of leaf-wetting hours over the threshold of 175 leaf wetting hours (LWH). Accumulation of LWHs has been variable and ranges between 65 and 135 LWHs, from petal fall. The accumulation across the region is slow and in the absence of significant rainfall, monitoring heavy dew and how long the trees remain wet is important.  LWH shorter than four hours will not trigger an infection. The accumulation of LWHs should be tracked from petal fall or whenever the last single-site fungicide was applied. Where single-site fungicides were applied at first or second cover, even few LWHs have accumulated.

Secondary scab
Do not use single-site fungicides, e.g., Flint, Rally, Indar, Merivon, if you have found scab in your orchard. The only exception would be if you already know you have strobilurin resistance to apple scab, then these fungicides, e.g., Flint (trifloxystrobin) or Sovran (kresoxim-methyl) could be used for summer disease management. Captan is the primary fungicide for managing secondary infections, summer disease and fruit rots once secondary infections are found.  It is recommended to compare the total amount of Captan applied this season to the maximum allotted amount per acre. Do not apply more than 40lbs of Captan 80 WDG per acre per crop cycle. A higher label rate is ideal if scab is present in the orchard, yet it is better to use a lower rate and more applications if you are approaching the seasonal maximum to avoid leaving fruit unprotected. Captan can eradicate many of the spore-producing lesions and reduce the risk of new infections. For eradication purposes, high rates applied in a dilute solution are most effective for optimal coverage in temperatures over 80°F.

Captan will remain effective for two weeks or 1.5” of accumulated rain for the full rate. The two-week interval can be extended during dry weather. If you are approaching the seasonal limit on captan, an application of the most effective SI (sterol inhibitor), Inspire Super (cyprodinil, difenoconazole), plus a full rate of captan in an orchard with active scab. The application of an SI or QoI (strobilurin), e.g., Flint (trifloxystrobin) or Pristine (boscalid, pyraclostrobin), fungicide on active, secondary scab lesions greatly increases the chance of resistance developing to those compounds, even when tank-mix with a full rate of captan. The best organic eradicant/protectant is lime sulfur, however, large amounts of lime sulfur at this time can cause tree stress and fruit russeting.

Codling moth
Codling moth degree days (DD) (base 50°F) from the biofix that occurred between May 13th and May 19^th are now between 650 and 725 DD, which means peak egg hatch for the first generation is winding down. Fruit with injury from codling moth should be visible. Another 275 to 350-degree days must accumulate until we reach 1000-degree days which mark the end of the first generation.  However, cool evening temperatures this week will not likely result in many moths flying, as we move into the end of the generation. Additional larvicides should only be needed if A. you received two inches or more of rain in the recent storms and codling moth traps were over threshold in the last seven to ten days, or if traps continue to go over a treatment threshold of five per week. If in the last two weeks your orchard had a late flight, there is a good chance these moths are likely hatching.

The insecticides we use to manage codling moth, while somewhat rainfast, will not be able to withstand more than two inches of rain. If wash-off occurs, review trap captures at 150-250 degree-days prior to the rain event to determine if a reapplication is warranted. Recently hatched codling moth larvae, while very small, do not drown during the severe rain events we have been experiencing, and any flight that exceeded threshold between 200-250 degree-days prior to the rain will require reapplication.

If weekly codling moth trap counts are 5-15/week, there is some flexibility on when to reapply an insecticide for hatching larvae. Captures exceeding 40-60/week are dangerous levels and does not offer much flexibility in timing an insecticide.

Not all adjuvants can improve insecticide rainfastness. Adjuvants that are surfactants allow sprays to seep deeper into a plantâ€s nooks and crannies but do not improve the pesticides†rainfastness. Other adjuvants that do not promote rainfastness are buffers or water conditioners that ensure the proper degree of acidity, and penetrants or activators like LI 700 or Regulaid that help systemic pesticides, e.g., neonicotinoids or Movento (spirotetramat), or plant-growth regulators to enter the leaf cuticle.

Adjuvants advertised as “stickers” like Nu Film P or Nu Film 17 may help improve rainfastness by creating a physical barrier over the surface of the pesticide. This prevents weathering of the pesticide by wash-off and ultra-violet oxidation since pesticides degrade from exposure by both rain and oxidation from ultra-violet rays. A sticker can be applied when rain is forecasted soon after a larvicide application. Stickers have a wide application range for different intended effects, but John recommends a median rate when using sticker-type materials. Find more information on spray adjuvants from the Penn State Extension here, https://extension.psu.edu/spray-adjuvants.

Maintaining a cover of a codling moth larvacide when rains are frequent support the benefits of using mating disruption. Even if a full rate of mating disruption is not used, a low rate of mating disruption would offer some suppression of codling moth under these current conditions. Table 1. Adapted from ‘Rainfast characteristics of insecticides on fruit†posted on June 7th, 2018, by John Wise, http://msue.anr.msu.edu/news/rainfast_characteristics_of_insecticides_on_fruit.

Lepidopteran species
Obliquebanded leafroller (OBLR) usually begin hatching in mid-June and the first OBLR have been seen in orchards throughout the region. These larvae are small-green worms with caramel to black head capsules. OBLR are moderate fliers, they fly better than codling moth, but not much better. Two traps per orchard should be used to monitor OBLR. Large flights now are a result of the overwintering generation not being controlled, which may lead to a higher second-generation population. These worms will be the offspring from the first flight of OBLR this season, which has been delayed. Worms at petal fall and first cover are overwintering larvae from last yearâ€s second-generation flight. In addition to feeding on foliage, larvae will also feed on fruit and can cause economic damage.  Altacor (chlorantraniliprole), Delegate (spinetoram) or Entrust (spinosad), applied for codling moth, except granulosis virus and mating disruption, should provide adequate management of OBLR. OBLR is resistant to many of the organophosphates and most of the neonicotinoids are not very effective on OBLR. Beneficial insects should also aide in suppression of this pest.  Second-generation larvae can be more problematic and more difficult to control than first generation OBLR.

Scouting for fruit and foliar feeding should begin seven to ten days after moths are caught in pheromone traps.  There are no established action thresholds and trap counts do not correlate well to the potential for feeding injury to fruit or growing terminals.  Terminal injury totaling 3-5% is a commonly used action threshold.  Look for discoloration and a few holes in the terminal or frass, which is evidence of OBLR activity. If terminals are set, then OBLR will be attracted to the fruit.

Potato leafhopper
Potato leaf hopper (PLH) adults have been observed in several orchards throughout the region, with a few nymphs appearing over the past couple days.  Adults are blown in on weather fronts each year, as they overwinter in Gulf Coast states.  Potato leafhopper adults and nymphs will inject a toxic saliva that causes damage to the leaf tissue.  The first sign of leafhopper feeding includes the cupping of leaves.  Further damage appears as a yellowing “hopperburn” of young terminal leaves.  Hopperburn can be described as a triangular yellowing or browning of the leaf tip.  This injury develops more rapidly during hot, dry weather and most damage come from nymphs.  Leafhoppers often move in a lateral fashion and will quickly go the underside of the leaf if disturbed.  Growers should be most concerned with PLH nymphs, and if needed, an application should wait until nymphs are more commonly observed, instead of targeting the adults.  The main priority is to monitor PLH on leaf terminals in younger trees.  The threshold for PLH is one or more nymph per leaf when hopperburn symptoms are appearing.  For more detailed information, please visit: http://labs.russell.wisc.edu/vegento/pests/potato-leafhopper/

Japanese beetle
The first Japanese beetle (JPB) are beginning to appear in southern Wisconsin. JPB females do not like to lay eggs in grass over three inches long and grass that is kept a bit longer may help prevent some egg laying within the orchard. Therefore, close mowing of the alleyways should be avoided when Japanese beetles are active in the orchard. Japanese beetle has a strong preference towards Honeycrisp. If populations are widely dispersed, it is advised to treat the entire orchard rather than making a targeted spray to the heavily infested blocks.

Japanese beetles (JPB) have a wide host range including many ornamental plants and horticultural crops including raspberries and grapes.  Within apples, JPB tend to have a preference towards Honeycrisp and can cause significant economic damage when left uncontrolled. Trapping JPB is optional and can help determine when to apply a repellent like Assail (acetamiprid), Surround (kaolin-clay) or Neem (azadirachtin). Insecticides used as a repellent should be applied at the earliest sign of JPB in or around orchards. Once JPB has been detected, traps should be taken down and disposed of immediately. After application, growers should scout adjacent varieties to make sure populations are not merely migrating to unsprayed varieties. Assail (acetamiprid) is an effective antifeedant and is toxic enough to eventually kill JPB adults.  The first migrants to move into the orchard will be most susceptible. Surround and neem will not be effective under severe pressure. If growers want to manage JPB without Imidan (phosmet) then early intervention is critical to successful JPB management.

One grower in Illinois reported a return of secondary pests after using carbaryl in 2017 to manage JPB. Carbaryl is only used for thinning and rarely used as an insecticide in orchards, because of the risk of damaging populations of beneficial insects. For most growers who have moved away from broad-spectrum insecticides, beneficial insects will be very susceptible to impacts from use of carbaryl, pyrethroids and organophosphates.

Organic and IPM growers also have the option of using neem products (azadirachtin). There are several different formulated products, in addition to using raw neem oil. Neemix and Aza-direct are two formulated products. Most labels do not talk about the ability to act as a repellant, but even though it will not kill adults, neem oil does repel Japanese beetle from immigrating into the orchard. Organic growers wanting to use a raw-neem oil with an emulsifier should check with their certifier to ensure the emulsifier is OMRI-approved. When using a formulated-neem product, the OMRI certificate can be downloaded and generally should be kept with the spray records. Do not apply neem oil during the heat of the day and apply in the evening or nighttime. There is also a Bacillus thuringensis product called BeetleGone, which is quite expensive but should be applied as a spot spray rather than a full orchard application.

Mites
Mite populations have been relatively low this season, despite poor weather for oil applications earlier this spring. Mite populations have also not exploded considering how strong of a mite hatch John observed during bloom, which suggests an abundance of predators in the orchard right now. Early mite injury can affect fruit bud formation for the mite next year and high populations later in the season can affect fruit finish, size, drop, and this yearâ€s fruit quality. Orchards with a light to moderate crop can sustain mite populations and pressure over a longer period and blocks with a normal to heavy cropload will need to pay close attention to mites.

Managing mites in August is never the goal and now is an important time to determine where populations exist. Sampling now will set a baseline for future population assessments. The hotter it gets, the faster mites eat, reproduce and eggs hatch. Many insects overwintered well and often we see first spider mite populations going over threshold after petal fall. This has not been observed yet and is not a guarantee they will not hit threshold. There may be more predators out there controlling population numbers. At this stage, rather than using a general leaf count to assess numbers, look at older leaves in problem areas like we do earlier in the spring. Using a 10x hand lens, look at the underside of leaves for mite eggs and assess about half a dozen leaves per tree.

Mite thresholds will increase from 2.5 to 5 mites per leaf in July and will increase to seven mites in August. Some growers are just beginning to see mites emerge and in addition to the wide range in performance of miticides, each orchardâ€s mite populations respond uniquely to a treatment. Mites do not travel between orchards, and you own your own mites, which means your mites have been exposed to whatever you have applied year after year in your orchard.

Threshold counts should include all motile mites, which may be difficult to see especially for smaller nymphs. European red mite populations tend to distribute themselves in high heat, allowing for easier counting. Magnification may be necessary to spot all young motile mites for an accurate count. Remember, predator mites can consume European red mite eggs and young. Beneficial mite predators at sufficient numbers on the tail end of a European red mite explosion will often lead to a higher ratio of red females to young or eggs, particularly motile young. Sequential sampling thresholds require inspecting leaves for all motile forms. The models were created to achieve no damage, so orchards with damage from mites may be past time for action. Download the sequential sampling forms in pdf form here, https://nysipm.cornell.edu/sites/nysipm.cornell.edu/files/shared/erm-sampling-chart.pdf

Some miticides work only as an ovicide and larvicide, whereas other miticides offer good contact activity on all motile stages. Where mite populations have exploded, miticides such as Zeal (etoxazole) and Envidor (spirodiclofen) will not offer the level of immediate knockdown of adults that is desired. Miticides with good contact efficacy include Acramite (bifenazate), Kanemite (acequinocyl), Nealta (cyflumetofen) and Portal (fenpyroximate).

If bronzing is still occurring while mite populations are below threshold, action is required to prevent further economic injury to the plant. This happens when a population of predators have remained active long enough to keep populations below threshold, yet enough mite feeding has occurred to cause leaf bronzing. Once leaf bronzing occurs, economic injury is happening to the tree and a miticide should be applied. This scenario is referring to what we call mite days, where the duration of mite activity is just as important as the actual population. This year may be an interesting one regarding mite days, since we have not had mite populations early on. If we reach threshold and still cannot see significant damage on any leaves, we may be questioning whether we need to make a miticide application.

Apple rust mites (ARM) have often been viewed as food for predatory mites, however, in high-density plantings and non-bearing trees, we are beginning to see more issues with ARM. The ARM will inhibit shoot growth on young trees and populations that appear while the trees are still pushing growth may need to be managed. Terminals are set on most trees and most non-bearing trees; however, some locations are still actively growing. This year we are beginning to see some damage from growing rust mite populations on terminals. Injured terminals will not recover and may not make it through the winter. This does not set the young trees up for a healthy fall and winter, if heavily damaged with rust mites or leaf hoppers. ARM is much less of a concern in mature trees or semi-dwarf orchards.

Envidor works well on rust mites but does not work on two spotted spider mites or European red mites. If these other mite species are a concern, other options are available that will manage all three. Make sure to read the labels, some newer products such as Nealta, do not control apple rust mites.

Apple maggot
Apple maggot (AM) have been caught as early as June 14th in some years. If you have had injury from AM or have early ripening cultivars, e.g., Lodi, yellow boards or red spheres for apple maggot monitoring can begin to be deployed. Yellow boards can provide an early warning system by attracting apple maggot during their feeding period. If bait is used in addition to visual traps replace volatile lures according to the manufacturerâ€s directions, e.g., seven to ten days. It is advised to set up a minimum of three traps per ten acres at the beginning of July; trap density should gradually increase to one trap every 200-300 feet along the orchard perimeter, as the season progresses. Locate traps along perimeter where wild hosts are present and near early ripening cultivars. Hang traps at eye level, and make sure they are visible. Traps are usually hung in early-season varieties that exist on the interior of block around July 4th. Putting a trap or two out now can give a good heads-up as well.

Water pH
It is important to be aware that highly alkaline water pH can make pesticides very unstable. The half-life of most pesticides in solution is at its greatest when the spray solution pH is between five and seven. For example, Captan has a half-life of ten minutes at a pH of 8.5, a half-life of 8-hours at a pH of 7 and a half-life of 32 hours at a pH of 5. Growers can use pH test strips and should be regularly testing water. A pH buffer should be added to the water if pH is too high, e.g., LI 700. For more information see: https://www.canr.msu.edu/news/effect_of_water_ph_on_the_stability_of_pesticides.

https://www.canr.msu.edu/news/rainfast_characteristics_of_insecticides_on_fruit

 June 15^th Call Stream: CLICK HERE

Table 1. Degree days and ascospore maturity downloaded on 6/15/21 from Cornell NEWA system. Find your local station today: http://newa.cornell.edu.

Regional roundup
The next couple of days will continue with temperatures in the 80s and 90s, however, low temperatures at night will dip into the upper 50s and by next week a cool front will move in with cooler temperatures in the 70â€s and possibly some rain. The current high-pressure ridge has prevented fronts from moving through that would normally develop into rain and storm fronts. There have been just a few convection related storms, some last week on Friday and Saturday morning and not a single NEWA station received more than 3/100 of an inch of rain. A few orchards received an inch of rain and are the exception.

Codling moth degree days (DD) (base 50°F) from the biofix that occurred between May 13th and May 19^th are now between 500 and 600 DD, which is the peak egg hatch for the first generation. Fruit with injury from codling moth and other pests should now be apparent. First generation moths will continue to fly for a few more weeks as there are about 1,000 DD in each generation. Most growers are applying their second larvacide at peak egg hatch and depending on how strong the flight is, a third may be necessary, but only if traps go over threshold in the coming week. This season the flight has been slow and steady, and traps have not always gone over threshold. If traps capture five moths in a week, they should be treated.

Plum curculio (PC) activity has been minimal in most orchards around the region, however, fresh PC injury was found this week in an orchard and is a reminder that PC will continue to be active through the end of the month, if there was not enough management during their emergence.

Management of summer diseases should begin after 175 leaf wetting hours (LWH) have occurred after petal fall. The accumulation across the region is slow and in the absence of significant rainfall, monitoring heavy dew and how long the trees remain wet is important.  LWH shorter than four hours will not trigger an infection.

UW Fruit News
There are several important articles growers should read regarding irrigation and weed management under drought conditions. As it relates to weed management, pre-emergent herbicides need water to be activated and if it is dry, the seeds will still germinate and push through the herbicide.  Post-emergence herbicides require actively growing weeds and in blocks where there is no irrigation, efficacy of these applications may be reduced.

Horticultural Issues
Drought resilience in cultivars
Use the current drought conditions to compare performance of different rootstocks and cultivars on trees less than ten years old that are not on irrigation. Look for flagging and leaf cupping that occurs under these drought conditions later in the afternoon. John is observing differences in trees less than ten years old, and these differences may translate into their ability to flourish over the next ten years. Trees that are showing less cupping and flagging in non-irrigated orchards, may be more resilient to climate change and weather-related stress

Frost
There is now a significant amount of fruit injury showing up that is not easily associated with any disease or insect, some of this injury has characteristics of a classic frost ring, but most is not. This injury is still likely from frost.

June drop
Some thinners did not thin as completely as desired. Most of this fruit should drop, but some may mummify on the tree and could be a source of fruit rots late this year and early next year. Look for fruit that is still hanging and but has stopped growing. This has mostly been observed on Gala, Honeycrisp and maybe some early fujis and this is suspected to be associated with NAA applications.

NAA and return bloom
Ethephon and NAA can be used to promote return bloom in all varieties but are particularly helpful in biannual varieties, like Honeycrisp. There has been more emphasis on using NAA than Ethephon as it seems to perform better for promoting return bloom in Honeycrisp. The flower bud formation for the next year can begin as early as petal fall in Honeycrisp. Any NAA that is applied at petal fall or on 10mm for thinning are also helping with bud formation for next season.

Michigan State recommends three applications of NAA that are applied at five, seven and nine weeks after bloom. Most growers are just now at the five-week mark from bloom and may begin making those sprays. The label recommends rates between 3-5PPM and to begin at five or six weeks after bloom with two additional applications made on seven to ten-day intervals.  NAA may be applied as a tank mix or alone. Some extension articles do recommend leaving out a surfactant or adjuvant if applied as a tank mix. If using a surfactant, reduce to 2.5ppm, though typically it is recommended to use 5ppm and leave out adjuvants and surfactants.

Resources:

• https://fruit.wisc.edu/2019/06/20/return-bloom/
• https://www.canr.msu.edu/news/use_summer_naa_to_enhance_return_bloom_on_apple_varieties

Summer pruning and leader singulation
Summer pruning always comes with a ton of caveats and the window is very narrow, typically a few weeks in early July. Our tree phenology is nearing what we generally observe in early July, with terminals beginning to set, fire blight risk decreasing, etc. This year the concern about timing summer pruning in July is it could increase risk of sunburn injury if drought conditions persist. Fruit with direct sunlight early in the season, somewhat acclimate to that exposure, if summer pruning in mid-July exposes otherwise shaded apples, this may be an increased risk of sunburn. This may also be observed as the canopy shifts as fruit grow and weigh branches.

There is always a risk of reinvigorating the tree anytime summer pruning is done and if completed too late, it can affect crop quality and fruit finish and stimulate growth too late in the season, where new growth will not harden off and will risk winter injury.  Only summer prune if the trees really need it and if your orchard is irrigated, has no fire blight, has a light crop, and has some varieties that are overgrown and need to have some larger branches removed. The benefit being, it is dry, and trees would heal and minimize exposure to canker fungi.

Regarding non-bearing trees, stimulating new growth through leader singulation is the goal. The heat and lack of rain is causing terminal buds to set earlier than normal and in non-bearing trees and newly planted trees, removing competing leaders right now can help stimulate additional growth, while still allowing time for trees to harden off later this summer.

If normal weather patterns return and we get rain, then summer pruning should be avoided next week. Avoid making big cuts over an inch or two inches that will require more than a week of dry weather to heal. If you have active fire blight, consider avoiding summer pruning all together. If your young trees have set terminals, it is not too late to water and fertilize the tree and get more growth out of the tree.

Chemical injury to foliage and fruit
Captan, sulfur and copper are toxic to plants and if these fungicides/bactericides penetrate the leaf cuticle or apple, there is risk of injury to the plant cells.  Johnâ€s concerns last week related to the millions of stomates that would be wide open during the heat to support transpiration.  When these stomates open, John is unsure how likely captan could penetrate the stomates but suspects that some of the injury we see to lenticels could be from captan injury. To mitigate risk of injury we can cut the captan rate. This same concern applies to other penetrating crop inputs such as NAA, Apogee and foliar fertilizers. Now that it is getting cooler at night, growers can resume applications of NAA, Apogee and foliar nutrients at night and early in the evening. The note in last weekâ€s blog post was specific to last weeks hot evening weather.

Disease management
Disease summary
There are some secondary scab lesions in the orchards and in the absence of heavy dew or rain, they will not create secondary infections.

IPM growers who applied a single-site fungicides at petal fall with captan, would have eradicated the first sooty blotch and flyspeck (SBFS) infections that may have occurred. These SBFS infections would have required rain after petal fall and require more than four hours of leaf wetting to be successful. Orchards that did not receive rain in the two weeks after petal fall would not likely have had an infection.

Canker diseases such as black and white rot that are normally spreading in the weeks after petal fall will not be spreading canker fungi, so long as weather remains hot and dry. We will see trees with existing canker infections take advantage of stressed trees where branches or the whole tree may collapse. You have some time to prune out black rot infected limbs, but until we get rain, there will be no spread of this disease.

Sooty blotch and flyspeck
Captan and Topsin (thiophanate-methyl) are the primary fungicides used to manage SBFS, especially where scab is also present. Where secondary scab is not a concern, the SDHI, Strobilurin and DMI fungicides may be used for SBFS. These are attractive because of their ability to also manage black rot and bitter rot. If the first application is Topsin or another single-site fungicide, this application will eradicate the infection when made after the accumulation of 175 leaf-wetting hours from petal fall.  A second application may be made using only captan to protect against future infections, this will allow growers to minimize the use of successive applications of single-site fungicides. The reapplication interval following the first application is dependent on rainfall and weathering of the material. A 2-3 lb. rate of captan is greatly reduced after two inches of rain or 21 days, higher rates may offer added protection. The potential for SBFS to develop resistance to single-site fungicides is minimal because new spores are coming in from outside the orchard and disease is a complex of more than 70 different pathogens. If apple scab is present, it is essential to avoid exposing these single-site fungicides to secondary scab populations.

Research completed on SBFS in the upper Midwest found that relative humidity (RH) rather than leaf wetness hours (LWH), is a better predictor of SBFS infections. It was found that 192 hours of RH above 97% was a better predictor than 175 hours of leaf wetness for our region. During the summer, dew usually contributes to more wetting hours than rainfall. Within the tree canopy, RH is more stable. Since we do not have instruments to gather RH at 97%, it is still recommended to use LWH. It is important to place the leaf wetness plates within the canopy to accurately record LWH. Remember to track RH and the NEWA station to assess whether the readings may be off.

Brambles are very common around orchard perimeters and in a few instances can be observed growing within the orchard around the base of older trees. The brambles include blackberries, raspberries or other Ribes species. This is where the pathogen overwinters and is where sexual development occurs. The chance of resistance to summer diseases to Topsin (thiophanate-methyl) or Incognito (thiophanate-methyl) is relatively small which is why we have been able to use these products for decades. It may be worthwhile to remove any of these species where SBFS may overwinter.

Summer fungicide applications for apple scab and black rot
If growers are wondering about reapplying a fungicide and no scab is present, the focus should shift to managing canker diseases, e.g., black rot, white rot, and fruit rots. John has observed small, round lesions that are a couple of millimeters in diameter, though are hard to know if they will continue to develop. Right now, a captan application with no scab in the orchard is hard to justify. Cover the orchard as needed for insect management rather than scab. This is all on the caveat that no scab is present, and growers may spot spray blocks with scab. Fungicides may be reapplied every ten days if there have been frequent rains to slow or reduce spread of summer diseases.

Powdery mildew
This season has been a strong year for Powdery mildew (PM) and has been observed in many orchards this spring on Honeycrisp, Cortland, and MN-55 (First Kiss). This disease flourishes in hot and dry conditions. Spores are easily washed from infection sites, but the fungus can grow on terminals, in the absence of rain. Once the terminals have set, PM stops growing, but the damage remains. If you fertilize and continue to water young trees, you will see some growth on these young trees and PM could continue to grow.

At one time, this a rather rare disease in the upper Midwest, but shoot infections are now commonplace. In the southern United States, powdery mildew is much more severe and can spread to fruit and cause russeting. At this point, there is no need to worry if powdery mildew appears on trees other than to note its location for next year. Single-site fungicides and sulfur provide protection against powdery mildew, whereas captan does not. Where there are no active-scab infections, single-site fungicides with efficacy on powdery mildew may be used with minimal concern of losing efficacy for primary scab management. Growers may have new trees that brought in PM or have some resistance. Sulfur may be used as a tank mix to mitigate resistance and organic producers may also use sulfur as a protectant against powdery mildew. Nurseries have different management programs, and it is important to keep an eye out for PM on first-year trees and to remember there is potential for this disease to develop resistance.

Insect management
Codling moth + trap maintenance
This season trap captures in non-mating disruption orchards are experiencing the classic B hump or secondary flight of the first generation of codling moth.  If you had a large flight ten days to three weeks ago, there may still be eggs hatching. In mating disruption (MD) orchards that use the high rate, e.g., 200+ disruptors per acre, a capture of more than one moth in a week could pose a thread. If you catch five moths in an MD orchard (meso or traditional), a larvacide should be applied.

The lifespan of our pheromone traps is dependent on three primary factors, the amount of pheromone load, the lure material or medium which regulates the pheromone release and the ambient temperature which can degrade pheromones during extended periods of high heat. Several extended-life lures exist with varying life spans. These should all be replaced at the beginning of July, and depending on their life span, they may last the rest of the season or may need to be replaced mid-August. Any 1x lure used for codling moth, obliquebanded and redbanded leafrollers, oriental fruit moth, lesser appleworm and dogwood borer should expect a lifespan of two to three weeks during periods of extended heat in July and August.

Table 2. Codling moth lure lifespan for first and second-generation flights.

¹Â http://msue.anr.msu.edu/news/using_pheromone_traps_to_monitor_moth_activity_in_orchards1

²Â http://entomology.tfrec.wsu.edu/stableipm/WorkshopPDFs/cmmonitoring.pdf

³Â No data was available on the lifespan during second generation, but we should presume decreased life of these pheromones based on average temperatures in July and August that have potential to decrease duration of pheromone release.

Insecticide options for codling moth and plum curculio
Trade name (active ingredient)	Plum curculio	Codling moth	Notes
Avaunt(indoxacarb)	X	X	Less long-term control of codling moth compared to Delegate or Altacor.  Rated as ‘fairâ€, reapply after 7-10 days.
Actara(thiamethoxam)*	X		Apply with CM insecticide, e.g., Altacor, Delegate.
Altacor(chlorantraniliprole)		X	Apply with PC insecticide, e.g., Avaunt, Actara.
Delegate(spinetoram)		X	Apply with PC insecticide, e.g., Avaunt, Actara.
Exirel(cyantraniliprole)	X	X	Same insecticide group (28) as Altacor
Belay(clothianidin)*	X	X	Use only if CM pressure is low, e.g., less than 10 moths/week/trap.  If Belay is used and pressure is high tank-mix with CM specific insecticide.
Assail(acetamiprid)*	X	X
*Note: If a neonicotinoid is used exclusively for PC and first-generation CM control it cannot be used alone for second generation CM and apple maggot (AM) control.  An imidacloprid, e.g., Admire Pro, Montana, Wrangler, tank mixed with Altacor or Delegate or applying Exirel alone will offer AM control and mitigate resistance concerns for CM; do not treat more than one generation of a target pest with any of these insecticides.

Obliquebanded leafroller and lesser appleworm
Obliquebanded leafroller (OBLR) and lesser appleworm (LAW) are two lepidopteran species that will require additional monitoring in orchards using mating disruption or in non-mating disruption orchards that have been applying neonicotinoids this spring.  Even though trap counts for CM have been down over the last two weeks, OBLR and LAW can cause economically significant fruit injury. If CM numbers remain low over the next few weeks and an insecticide is not required, make sure to not overlook these two insects. There are no thresholds and therefore no recommendations for spraying if “x” number are captured, rather trap counts are relative reflections of the population. If the OBLR trap catches quite a few, there is more pressure and the same applies for LAW. Provisionally, if less than ten LAW are captured, John would not recommend applying an insecticide. However, if catching 25, note when that flight occurred and assume that in around 250 DD or in two weeks, LAW larvae will hatch out and an insecticide application may be necessary. Obliquebanded leafroller larvae begin emerging at 700-degree days base 43 from biofix. Scout for larvae by looking at terminals, or younger trees. John would recommend an application for any OBLR catches over ten. Remember, these applications need to fit in with CM resistance management. Assail (acetamiprid) is effective on LAW but is not on OBLR.

OFM or LAW lures may be used and virtually all moths we catch are LAW.  John is using almost all LAW lures and am catching more LAW than ever, with high counts upwards of 300 LAW moths in the last two weeks. Since these cause the same damage as CM, even though these do not go to the core, they are a problem and there is no threshold.

The OBLR flight has traditionally flown significantly in a short time and then not fly for a while. This year the flight seems to be a bit slower, e.g., 50 in a trap over ten days. Most large counts occurred in the first week of June. Depending on when the trap went out, this flight may not have been captured. You will need to assess larval hatch in terminals if there was a significant flight. It is too hot for OBLR and growers may not need to spray for OBLR, just keep scouting for OBLR hatch and wait until we see evidence rather than applying a larvacide ahead of time.

Tarnished plant bugs and stink bugs
Tarnished plant bugs (TPB) and a few stink bugs have begun to appear in orchards as the understory begins to dry up. These observations have mostly included stink bug egg hatch and adult TPB moving into trees as ground cover begins to dry up.  Along with these pests, could be a wide array of other insects that come into trees, generally not worried about some of these other pests. However, TPB is a pest to add to the list to scout and spray for.

The Lake Ontario IPM program recommends starting monitoring aphids at petal fall and continue until terminals harden off (late July or August). Check 100 terminals in a 10- 15-acre block weekly throughout the summer. Pick 10 terminals per tree on 10 trees randomly, without visual bias towards infested terminals. The action threshold for green apple aphid is 400-600 aphids per terminal on 10% or more of terminals checked. Be sure to look for predators when assessing aphid populations in orchards.  If more than 20% of the aphid colonies have natural enemies, delay, or eliminate an insecticide application. Resample orchards with weekly, to determine if predators are providing control.

Wooly apple aphid
The first wooly apple aphid (WAA) colonies have been showing up in the last week and along with them signs of parasitic wasp activity active on these colonies. Older trees with scaly bark are more likely to have this pest. Scout for developing colonies on pruning cuts and vegetative shoots. There are many effective beneficial insects which manage WAA, but an insecticide may still be necessary before third cover, where WAA is a chronic problem. Since terminals are beginning to set sooner this year, products such as Movento (spirotetramat) will be less effective.  Beleaf 50 SG would be an alternative product to use if WAA colonies begin to grow over the next few weeks and are not managed by predators.

Parasitoids and predatory insects
There are lots of parasitic wasps active on WAA and hoping they will lay eggs on aphids and leafroller larvae. These parasitic wasps lay their eggs inside the aphid and once we see the hole in the aphid, the parasitic wasp has already hatched. Many growers have been using neonicotinoids this spring and it seems these parasitoids are not being impacted by this class of insecticides, but this is not known for sure. If the next cover can be delayed a few days this week to give these parasitoids a few more days, that would be ideal. The risk of stretching codling moth sprays to 17 days may be okay, as John thinks there has been some mortality of CM eggs due to the heat.

Dogwood borer
The Dogwood borer (DWB) flight has begun and growers with two to ten-year old trees should be monitoring this pest. Mating disruption is available in Minnesota and Wisconsin and requires a ten-acre minimum to treat. The labeled rate for IsoMate DWB is 100-200 per acre with a maximum of 2,721 per acre. In comparison, CM mating disruption twin tube has 100-200 per acre with a maximum of 392 per acre. Growers do not need to go up to this number but might consider putting out more than the 100-200 per acre. Larry Gut, Michigan State, discussed that OBLR and DWB are more like CM in terms of difficulty in being controlled with mating disruption. All three are localized fliers, where insects like OFM or LAW are much easier to disrupt. This reflects their flight range. There are alternatives to mating disruption for DWB but is quite costly and impactful, e.g., trunk spray of Lorsban (chlorpyrifos).

Potato leafhoppers
The first Potato leafhoppers (PLH) were observed in northeastern IL in the upper Mississippi River Valley and are problematic on non-bearing and high-density orchards. Potato leafhoppers come to the region during spring storms where warm air masses from the Gulf of Mexico pick them up, as the system moves north. To date, numbers reported in other host crops, as per the Wisconsin Department of Agriculture Trade and Consumer Protection Pest Bulletin, were still relatively low. The first large leafhopper immigration into orchards tends to occur after the second cutting of hay, which is happening now.

Mites
Apple rust mites are exploding in the last nine days on trees and should be scouted and consider a miticide if populations are rapidly increasing. European red mite (ERM) populations have been quite low and stayed low and are seeing lots of mite predators.

 June 1^st Call Stream: CLICK HERE

Table 1. Degree days and ascospore maturity downloaded on 6/1/21 from Cornell NEWA system. Find your local station today: http://newa.cornell.edu.

Regional roundup
Summer must be here, as by June 5 and 6 the temperatures are to reach the 90s and will accelerate insect activity. Expect plum curculio and codling moth to become active during these warm nights.  Other summer pests such as San Jose scale, aphid, dogwood borer, black stem borer will become active too. 297 – 332 DD base 50 for the month of May.

The sky is not falling
We have at least 16 growers in AppleTalk that have been at this for just a few years. This next paragraph is for you! I had a conversation with a trusted grower who returned to the farm to grow apples the same year I started scouting; 14 years ago. They commented that John and I approach every pest with a sense of urgency, as if the sky is falling, when in reality it is not. We take this approach because most advanced IPM strategies using low-risk insecticides have a very narrow window for their effectiveness. The reality is tree nutrition, crop-load management, sales and marketing, are also equally important. Most beginning growers can produce a great crop if they stay focused on codling moth, plum curculio, apple maggot, apple scab and fire blight. One way to set priorities is to ask the question: Will this pest impact my crop quality or my tree health? A pest that will have a minor impact on crop quality or tree health could perhaps get a pass now and then, but not always. Setting the priorities is up to you, we want to make sure that AppleTalk is giving you the right information to do so. Please let us know what topics you would like addressed or additional information you need to set your IPM priorities.

Horticultural
Nutrient deficiencies
Make note of discolored foliage on terminal growth and which cultivars are affected and consider taking pictures for future reference. This may be helpful when collecting leaf samples for nutrient testing.  Trees that are showing excessive symptoms of nutritional deficiencies should have separate samples collected when you take tissue samples for nutrient analysis.

Soil borne pathogens
Most growers do not have to worry about too much water this year, however, those with heavy soils or who frequently irrigate, can be at risk of having too much water. Over watering can cause root death if a hypoxic environment is created, i.e., too much water deprives roots of oxygen. Other problems that can result from too much water include development of root diseases such as phytophthora.  Impaired root function also can appear as discolored, small, or wilting foliage at tops of trees and have begun to appear at the tops of trees.  These abnormalities will appear more intensely due to the heat and high evapotranspiration rates and show up on the tops of trees and are less likely to be present on lower limbs.

Irrigation
Estimate your current water deficit by totaling precipitation from February 1 through May 31 and comparing that to the normal precipitation for those four months. This will establish a baseline for your water needs going forward. If your current needs are being met through timely rains, but you have a deficit of four inches from February through May, begin or continue supplemental watering, so when apples are sizing in August there will be sufficient available water deeper in your soil profile. Even though many orchards have received 3.5 to 5 inches of rain in the last two weeks, the subsoils are still abnormally dry and will cause the surface soil to dry out faster. In our region approximately nine inches of precipitation accumulates between February 1 and May 31, and we have only received six inches to date. Warm weather Friday, June 4 to Monday, June 7 will lead to significant evapotranspiration. Going forward, high density orchards need an inch of water a week either from rain or irrigation.

Return bloom
In the most recent UW Fruit News there is an article about promoting return bloom. One possible reason due to poor return bloom was due to the dry period in the 45 – 90 days after full bloom, which is the time when fruit buds are formed.  This was an excessively dry period and if there was not irrigation, may have resulted in poor return bloom this year.

Crop assessment
While hand thinning or evaluating fruit your fruit load, look for fruit abnormalities due to freeze damage or poor seed-set. Not all freeze damaged apples show a classic “frost-ring”. Fruit may be misshapen, lopsided, have surface spots or discoloration. You can do a seed count in affected fruit to verify freeze/frost damage as the culprit. Symptoms will be more pronounced as fruit sizes beyond 20 mm.  Besides frost rings, other injury can include misshapen fruit or discoloration on the skin.

Diseases
Black rot
The upcoming heat and dry soils will bring out symptoms of old infections from canker fungi, i.e., black rot or white rot, Phomopsis, nectria canker, etc., where we may see collapse of scaffold limbs. There is no urgency to prune and remove these diseased limbs, but they are sources of inoculum and can spread via trauma from wind or hail.

Apple scab
Primary scab season is over! However, most of our infection periods occurred after May 18^th and secondary lesions of apple scab which will be visible on both upper and lower leaf surfaces will take another seven to ten days to appear.  It is advisable to keep fungicides on seven-to-ten-day intervals before stretching to a summer schedule.  Once it is certain there is no scab in the orchard, then intervals may be stretched.

Fire blight
Despite the dry weather, there has been excellent shoot growth this spring and growth may slow down if nighttime temperatures remain warm. Warm night temps will cause trees to burn up sugars they accumulated during the day and exhausting these sugar reserves is what slows growth. Vigorous trees and trees that have had lots of growth will be more susceptible to shoot blight infections.  One strategy that some growers have used is to apply Cueva and Double Nickel preventatively from petal fall until terminals set.  However, even though this tank mix is not supposed to cause fruit resetting, the risk is still present.  A Cueva and Double Nickel tank mix will be much more effective if applied preventively and will stop the development and further spread of shoot blight after symptoms appear. Streptomycin should not be used unless you have trauma from hail and must be applied within 24 hours.

Insects
Codling moth
In 2020 many orchards experienced an enormous flight at petal fall and then never saw high codling moth trap captures later in the season. This year the codling moth flight began as a trickle and has remained as such. The warm weather may result in a flight, and everyone should check traps on a tighter interval this week to see if there is a bump in the flight over the week.

The codling moth degree day model suggests that at 250-degree days from our biofix 3% of the population is hatching; at 350-degree days, this increases to 15% egg hatch; and between 450- and 550-degree days from biofix is when we have peak egg hatch. There are 1000-degree days in each generation and similarly, by 750-degree days only 15% of the remaining population is hatching and by 900 it is down to 3%. This makes a bell-shaped curve, and the goal is to get the most value out of each larvacide application. This means making sure we are covered at peak egg hatch and then there is some flexibility on the front and backend of the generation, re additional larvacide sprays.

If initial trap captures were more than ten in a week, per trap, the larvacide may be targeted right at 250-degree days. If trap captures were less than ten in a week and right around the threshold of five per trap per week, waiting until 350-degree days will be better.  If the larvacide is timed at 350 DD from the biofix, approximately 60% of the egg hatch will be targeted by one application. If applying at 250 DD only 3% to 30% of the population will be targeted.  Last year orchards that had high numbers right away, it was important to time the larvacide at 250 DD. This year many orchards will be safe waiting until 350 DD to apply a larvacide.

Many orchards are applying their last plum curculio spray this week.  The timing of this application is likely ahead of 250 DD from CM biofix, and likely will not have active residue by the time 350 DDs have accumulated. Insecticides such as Belay or Avaunt are rated as only fair on codling moth. If your codling moth population is low and considering the minimal egg hatch at 250 DD, these insecticides applied for PC may offer adequate protection against codling moth for a few days. If you have caught high populations since biofix, may not want to rely on these insecticides.  Please see last weekâ€s notes for a more detailed discussion on insecticide options.

Plum curculio
The prolonged bloom has made it challenging to use McIntosh petal fall to predict the emergence and duration of plum curculio season. What is the most important thing to remember is an unmanaged population of PC can remain active well into the end of June. All the degree day model helps us understand is when movement of this pest from the surrounding woods and hedges should end. The conditions this year highlight the importance of PC scouting both on the edge and interior.  I have found PC injury in almost every orchard I have been to and in many instances, it was quite hard to find, but it was there. Even if we loosely lean on the degree day model of 308 DD, base 50°F, from petal fall, most orchards will have accumulated enough degree days by early next week that no new PC should move into the orchard. If your current PC insecticide is ten days or more old, reapplying a perimeter or a full cover ahead of these warm temperatures is essential. Another option is to be vigilant with scouting and wait until the earliest signs of new injury appear and then apply a cover. Either way, there is no substitute for PC scouting this next week, so set aside some time in the morning before it gets too hot and look around the perimeter and interior of the orchard for the crescent shaped scar.

Secondary insect pests
San Jose scale
An economically significant pest, yet not a problem at all orchards, infestations of San Jose scale (SJS) result in fruit injury and a slow decline of the tree over time. Feeding on the fruit induces local red to purple discoloration around feeding sites and results in a blemish. There are two generations per year and crawlers from the first generation will be emerging soon.  Dormant oil applications are important to targeting scale, in addition to mites. If SJS has been a problem in the past and oil was not applied this year, monitoring this pest should be a priority. If you have never had an issue with SJS, keep an eye out for this fruit injury.

Monitoring sites maintained by Michigan State University began catching males in pheromone traps two weeks ago. Typically, we have not monitored the males using pheromone traps and rather rely on monitoring crawlers using tape. Monitoring with tape is more useful, as insecticides for crawlers have a narrow window and monitoring with the pheromone trap is not an adequate substitute for monitoring crawlers. Based on the MSU captures, it would suggest SJS will be hatching in the next two weeks. Scale and mites have a higher temper threshold for their development, so similar to using an upper limit of 86 for codling moth, scale and mites have an upper limit in the low 90s for their growth and development.

Monitor known hotspots with black electrical tape applied to infested scaffold branches. Place the adhesive side towards the tree and wipe a thin layer of petroleum jelly on the outside of the tape. Double-sided tape can also be used. If populations are high, concentrate a few tapes on younger limbs (2-3” diameter) in areas with greatest pressure and on the sickest looking trees. Last yearâ€s scale will be concentrated near newer growth and increasing the number of monitoring sites may help eliminate false negatives. Low-trap captures do not reflect overall pressure, i.e., false negatives, rather they may indicate the beginning of the hatch. First generation SJS hatches over a narrow period, while second generation hatches over a longer period. Use a hand lens with at least 10x magnification to scan tape for oval, bright-yellow crawlers. Catches of 10-15 crawlers in a couple of days or 10 crawlers on one tape, may warrant an application for management of SJS.

If a special application for SJS is warranted, e.g., evidence of crawlers, Esteem (pyriproxyfen), Sivanto (flupyradifurone) or Centaur (buprofezin), may be applied. Esteem is an insect-growth regulator and will manage OBLR, CM and RBLR. Do not treat at first-crawler detection, rather at 150-200 DD after crawler emergence.

Organic SJS Management
Nothing really changes for organic growers needing to manage SJS, except the insecticide selections, which have been limited up until now. Typically, SJS is not as much of a problem in organic systems, yet plenty of organic growers have mentioned SJS issues over the years. If you are one of these, consider using Grandevo. Trials conducting at Cornell in 2017 showed very similar levels of SJS control when compared to conventional insecticides. There is a supplemental label for SJS management, meaning you will not find SJS on the regular Grandevo label.  Supplemental label: https://s3-us-west-1.amazonaws.com/agrian-cg-fs1-production/pdfs/Grandevo_2EE1j.pdf.

Obliquebanded leafroller (OBLR)
OBLR have two generations per year and overwinter as larvae and emerge in the spring. The young larvae then feed on leaves and protect themselves by rolling leaves with webbing where they are concealed from outside threats. Once the larvae have reached 4th instar, pupation will then occur inside the rolled leaf and lasts 10-12 days. In the past week, pupae have been observed and flights will likely occur soon. Moths then emerge from Mid-June through Mid-July and will quickly mate and lay eggs. Females can lay up to 900 eggs in a weeklong oviposition period. Eggs take 10-12 days to incubate and emerge at 350-400-degree days base 42F from initial trap biofix. The second flight typically occurs in mid to late-August.

If OBLR traps have not been hung, one or two traps per orchard should be placed this week. Once the OBLR flight has been observed, additional larvicides for CM should consider efficacy against this generation of OBLR. Obliquebanded leafrollers are like CM in that they are poor fliers and therefore may need extra traps in the orchard. Most growers only deploy one or two OBLR traps, which may not be enough to accurately capture the population density and pressure. However, this is not often a concern, when larvacide for codling moth are being applied.  Where mating disruption is used and there is a goal to minimize additional insecticides, more OBLR traps should be hung in the orchard to adequately sample the pest. Typically, the second generation can cause injury at harvest and larvicides applied during their first generation can significantly reduce summer populations.  If trap counts are high, e.g., more than 50 in a week, then larvicides for OBLR may need to be applied.  Note: There is no threshold for OBLR traps, this is just a nominal number based on what we typically observe under high-pressure scenarios.

Most neonicotinoids (Assail, Belay, Actara, Imidacloprid) will not suppress populations of OBLR. Belay (clothianidin) is one exception and is labeled for OBLR, but not other leafroller species. Belay has been a popular neonicotinoid to use, where plum curculio and first-generation codling moth management overlap. Growers who have used Assail (acetamiprid) or other neonicotinoids for plum curculio or first-generation codling moth should note these will not manage populations of OBLR or other leafrollers. Two popular classes of insecticides which will manage codling moth plus the spectrum of leafrollers and other internal-feeding lepidoptera, e.g., oriental fruit moth and lesser apple worm, include spinosyns, i.e., Delegate (spinetoram) and Entrust (spinosad) or the diamides, i.e., Altacor (chlorantraniliprole) and Exirel (cyantraniliprole). A good option for organic growers would be to apply Bacillus thuringiensis (Bt) for OBLR plus the codling moth, e.g., Virosoft or CYD-X (Cydia pomonella granulovirus).

Dogwood borer
Borers are an occasional, yet problematic pests of apple trees and especially dwarf trees.  Some semi-dwarf orchards live for many years with significant DWB infestation and yet show no signs of decline; and conversely, DWB can easily take down a dwarf tree if left unmanaged. Usually, DWB injury is found right above or around the graft union. DWB have also been observed in the scaly bark that is not covered by tree guards, e.g., winter injury or herbicide injury, or even on pruning cuts just above the tree guards. Small diameter dwarf tree, e.g., three to six-years old, are more prone to girdling that can be caused by continuous infestation; feeding often needs to happen for several years before trees shows decline in vigor and possible death. Even if feeding does not impact the vigor of the tree, it can produce an entry point for disease, e.g., black, or white rot.

Pheromone traps for DWB should be placed in 2–5-year-old trees at height of 3′-4′. The DWB pheromone casts a very wide net and attracts multiple species of native clear-wing moths. If moths are caught in traps, they need to be appropriately identified to confirm species. There is not a trap-based threshold for DWB, rather if you are catching DWB adults you need to be looking for evidence of DWB larvae, e.g., frass around the graft union. Initial stages of DWB infestation may be random, damage may not affect tree immediately but four to five years down the road trees will begin to decline. Trapping gives us an early warning system to begin scouting, rather than waiting for visible symptoms.

Management options are limited and a trunk spray of chlorpyrifos is the currently the best option for suppressing existing infections.  Trunk sprays require large volumes of water and high pressure to thoroughly coat the bark. If good coverage is achieved effective protection can be achieved for 2-3 years. Low pressure backpack sprayers are not suitable for this application, and neither is using the bottom nozzles of an airblast spray.  Applying chlorpyrifos with a hand-wand attachment to the main sprayer is the best option.

Spider Mites
The approaching heat will accelerate development of European red mites (ERM) and two spotted spider mites (TSSM). The ERM have dispersed from the sites where they hatched and are beginning to disperse through the canopy. Right now, the priority is to scout historical hot spots or varieties that did not receive an oil application. Keep an eye out for orangish-red or amber colored mites or eggs, as these are predatory mites (the good guys).

Orchards that did not have good opportunities to apply oil and may see more mite activity this year and may be a problem sooner rather than later this year. Do not delay mite observations if oil was not applied and since most miticides donâ€t take down large populations, early intervention when populations hit their threshold is important.

Black stem borer
Black stem borer is an ambrosia beetle that has slowly been growing in prominence as a pest of economic importance in the northeast United states.  Mostly a problem in non-bearing trees, BSB only attacks trees that are stressed to the point where they begin to produce ethanol. Adult females are attracted to this ethanol and hollow a gallery in the trunk of the tree several inches above the graft union. Young larvae do not feed on the tree, rather on a fungus that grows within the gallery.  Tree decline is caused by the females which essentially girdle the trunk from their tunneling.

In 2020 traps placed at 18 orchards throughout WI caught high numbers in many locations, yet no one has reported wide-spread tree decline.  Some of the highest numbers came from orchards that mostly have semi-dwarf trees that are quite mature with a large trunk diameter.  It may be possible these trees are thriving despite an infestation of this ambrosia beetle.  Monitoring was completed using an ethanol pouch and it may also be possible the trap drew in these beetles from the surrounding woods

The best strategy is to prevent BSB infestations through proper tree nutrition, irrigation and crop-load management, as if trees are not stressed, they will not attract BSB.

BSB was monitored in the following counties:

Japanese beetle
Very warm soils have resulted in early flights of June beetles and John is predicting an early emergence of Japanese beetles.  Monitor wild grapes if available or Honeycrisp for early signs of JPB.  This will be addressed in greater detail in the coming weeks.

May 25^th Call Stream: CLICK HERE

Table 1. Degree days and ascospore maturity downloaded on 5/24/21 from Cornell NEWA system. Find your local station today: http://newa.cornell.edu.

Regional summary
Warming temperatures and increasing likelihood of rain across the region will bring increased risk of secondary scab infections; the first signs of plum curculio activity and the start of the codling moth flight. Fire blight risk is minimal for varieties past petal fall, but non-bearing trees with bloom are at risk.

Diseases
Apple scab
The NEWA models show all locations in Table 1 are at or past 95% primary ascospore maturity and remaining spores will be released when at least 0.1” of rain is received. Infections will occur if temperatures are above 50°F during the rain and leaf wetness is sustained. Orchards north of Eau Claire, WI and along Lake Michigan, such as Mequon, WI are only at 70% primary ascospore maturity. The total number of scab infection periods varied between four to eight, and most occurred in the last ten days. It was considerably warmer during these recent rains and scab lesions appear within 14 days. Scab lesions have already been found in southern Wisconsin and rain will spread secondary infections. Orchards should be covered for scab ahead of the upcoming rain.

When scouting, look for lesions on the backside the of the leaf, this is where primary scab infections tend to show up first. Scab lesions found on the top of leaves tend to come from secondary infections, but this is not universally true and primary lesions on the topsides of leaves can appear. To better determine when the infection occurred, look at the age of the leaf and location along the length of the growing shoot. This is indicative of when the infection occurred. A lesion on a newer leaf reflects a scab infection that happened more recently than a lesion on an older leaf at the beginning of this yearâ€s growth.

Powdery mildew
Even though the weather patterns have been oscillating between hot and dry and cool and wet, the periods of hot weather have resulted in significant powdery mildew infections for some orchards. Powdery mildew (PM) has been observed on Cortland, McIntosh, Gingergold and Honeycrisp. Remember that captan and EBDCs (mancozeb) do not protect against powdery mildew. Sulfur is the only “broad-spectrum protectant” active on powdery mildew. When temperatures are not solidly in the 80s°F, sulfur can more safely be applied. When temperatures are in the 80s during the application and drying, the risk of crop injury increases.

The strobilurin, sterol inhibitor and SDHI fungicides are all options but have varying efficacy between “Fair”, “Good” and “Excellent”. If you are seeing powdery mildew or have a history of powdery mildew a sterol inhibitor such as Indar, Procure, Rally and Topguard are all rated as “Excellent” and would be the best option. If you have powdery mildew or scab resistance to the sterol inhibitor fungicides, then a strobilurin or SDHI would be the next best option. Fungicides with a good rating include: Flint, Luna Sensation, Fontelis, Merivon and fungicides with a “Fair” rating include Aprovia and Inspire Super. Depending on what other diseases need to be managed, a “Good” rated fungicide might be just fine.  Unless there is a significant amount of scab pressure and minimal powdery mildew pressure, avoid a “Fair” rated fungicide.  This table is on page 53 – 54 of the 2021 – 2022 Midwest Fruit Pest Management Guide.

Cedar apple rust
Across southern Wisconsin, John has observed cedar galls that have already matured and released their spores. Locations to the north or northeast may still have active cedar apple rust galls. The CAR galls resemble orange golf balls which can grow more than two inches in diameter. When they are mature, they swell and produce telial horns during rainy weather which release spores. Once the spores are released, the telial horns collapse and eventually the gall will fall off. Cedar apple rust cannot spread from apple to apple or from red cedar to red cedar. The fungus must go through the two-year life cycle, alternating between hosts. The infection period for CAR is between tight cluster and first cover. Most infections occur when infected eastern red cedars are within a few hundred yards and spores land on young apple tissue. Symptoms appear one to two weeks after the infection. EBDCs applied from tight cluster to first cover provide good control when applied as a protectant but offer no post-infection activity. However, we have still observed CAR infections in orchards using the extended spray schedule of EBDCs through petal fall. Susceptibility of cultivar and proximity to an infected host will influence disease pressure. Unlike scab, rusts require an alternate host and inoculum is not reflective of how much rust was in the orchard last year. The strobilurins, SDHIs and sterol inhibitor fungicides offer varying efficacy on rust, check your label if you need additional rust control. However, none of the fungicides would stop the transmissions of spores from leaves of apple trees back to red cedar.

A note on EBDC fungicides
The EBDC fungicides mancozeb sold as Roper Rainshield, Manzate Pro-Stick, Fortuna, etc. have a 77-day pre-harvest interval, but may only be applied up to this 77-day PHI at the 3 lb. rate. The pre-bloom schedule allows for four applications up to a total of 24 lbs. per acre per season. The extended-spray schedule allows for up to seven applications at 3 lb./acre for a total of 21 lbs. of mancozeb for the season and allows you to apply up to the 77-day PHI.

A common comment I have heard is growers applying 4 or 5 lbs. at some point during the season, if this is done, you can no longer follow the extended spray schedule and you are bumped into the “pre-bloom schedule”.  Based on the label instructions, at no point should 4 or 5 lbs. of mancozeb be applied, either apply 3 lbs. or 6 lbs. per acre. While it is not illegal to apply 4 or 5 lbs. it is somewhat a waste, since it bumps you out of the extended spray schedule and the only benefit is that you saved a few dollars per acre.

Fire blight
Newly planted trees continue to push out blossoms and some growers are still reporting the occasional bloom appearing. There is a serious fire blight risk for these newly planted trees and these blossoms are susceptible to infection from rapid bacterial growth that will occur during this hot weather. It is important to remove the blossoms or treat these young trees with low doses of copper or streptomycin if there is a fire blight infection.

Insect management
Codling moth
Low numbers of codling moth have been reported over the last ten days. However, a strong flight establishing our biofix in southern Wisconsin occurred on May 19 and 20. Growers to the north should expect a flight with this warm weather, if it has not occurred already.

For those who may be new to codling moth management, we define a “biofix” as marking the first and significant-sustained flight, where moths are captured multiple days in a row or exceed a threshold of five moths per trap per week. Once a biofix date is established, begin tracking degree-days (base 50°F) and monitor traps weekly. If you are calculating degree-days by hand, be aware that codling moth has a top developmental threshold of 86°F, which means all temperatures above 86°F should be counted as 86°F, e.g., a high of 95°F would be changed to 86°F degrees, if calculating by hand. Degree days are also available from your nearest NEWA station here, http://newa.cornell.edu/index.php?page=degree-days.

Codling moth fly between 6pm and 11pm when wind speeds are between three and five miles per hour and when temperatures are above 62°F, without rain. Assign the biofix date for the warmest, calmest night. When checking traps, fluttering CM had likely flown within the last 48 hours. Most female CM can live for seven to 14 days yet will mate and deposit most eggs on the evening they emerge. Every day that a sexually viable female emerges and is not able to fly, egg fecundity is decreased by 20%.

Growers using mating disruption do not need to shut down 100% of mating for it to be effective. When we vastly reduce the number of moths exposed to our insecticides, this helps improve the efficacy of the insecticides that are applied and reduces selection pressure which can mitigate resistance risk.

Resistance management considerations
Codling moth is a significant global pest of apples. While not present in every apple production region of the world, all locations around the world with codling moth have reported resistance to one or more insecticide mode-of-action. In the United States, resistance to the organophosphate classes of insecticides is the most common example of resistance. Growers in Michigan have reported codling moth resistance to insect growth regulators and Avaunt (a common insecticide we use for plum curculio). Codling moth resistance to the neonicotinoids has been reported in Europe. The point is codling moth is a highly adaptable species and considering that three – four insecticide applications are sometimes required for the first generation and two or three applications for the second generation, resistance management is paramount! There are a lot of insecticide options for codling moth, but some of our other pests do not. This positions neonicotinoids as the primary organophosphate and pyrethroid replacement for plum curculio, aphids, plant bugs, Japanese Beetle. If we add in these pests plus codling moth, it could be quite easy to accumulate six neonicotinoid applications during a season. Even though these are not all targeting codling moth, we need to consider non-target exposure when applying insecticides for these other pests.

Neonicotinoid resistance management for codling moth:

• Option One: Neonicotinoids used for first generation codling moth, plum curculio, rosy apple aphid, green apple aphid and Japanese beetle. For the second generation of codling moth, diamides (Altacor or Exirel) or spinosad (Delegate) should be used.  Apple maggot may be controlled with Exirel and neonicotinoids would need to be used sparingly and only target apple maggot and not codling moth. In this scenario Wrangler (imidacloprid) would be a preferred apple maggot insecticide over Assail (acetamiprid).  Assail and Wrangler are neonicotinoids and Wrangler has no efficacy against codling moth. Mating disruption is also an option!
• Option Two: Altacor, Exirel or Delegate are used for first generation codling moth. Plum curculio would be managed with Avaunt and the neonicotinoids Assail may be used to manage second generation codling moth and apple maggot. The other neonicotinoids may also be used to manage late activity from Japanese beetle and apple maggot. Where rosy or wooly apple aphids are a problem during first generation codling moth, Beleaf 50 SG may be applied. Beleaf 50 SG has a supplemental label for use on first generation codling in Wisconsin. Unfortunately, this label has not been extended to growers in Minnesota, Illinois, or Iowa. So, make sure aphids and plant bugs are the target, but it would certainly be active on any codling moth present. Mating disruption is also an option.
• Organic Management: Organic codling moth management should absolutely be based in use of mating disruption. However, insecticide applications may still need to supplement MD in organic or IPM Orchards.  Organic growers should consider timing applications of the codling moth virus (Cydia pomonella granulosis virus) sold under the trade names Virosoft and Cyd-X. Entrust, PyGanic, Grandevo and Venerate are all OMRI approved insecticides labeled for codling moth and several other important pests of apples. The same rotational approach should be considered when using these on codling moth or for other insects.

As resistance builds, the effects are not immediately visible for a few years.  The number of successful resistant worms that survive are so low that problems do not appear during scouting or on the pack line. Evaluate the trap captures between first and second gen CM; the first sign would be larger populations of adults during second generation vs. second generation.

Plum curculio
Plum curculio movement has begun, and injury has been found in NE Wisconsin and several locations in southern Wisconsin.  It should be expected that more injury from this past weekend to become visible. Thursday and Friday are expected to be very cool and could slow PC movement until nighttime temperatures are back in the 60s. The last several nights have been ideal for oviposition injury. In the past we have discussed scouting early sizing varieties first, but as more fruit reaches 10 mm in size, any fruit at or above 10mm will be susceptible to PC oviposition. At this time, scouting should not be limited to only the perimeter and the interior of smaller blocks should be scouted and larger blocks should be scouted ten to fifteen rows in from the edge too.

Please make note of the 95% petal fall date and report back to us. Tracking degree days from petal fall may be used to predict when their emergence from overwintering sites ends, which occurs after 308 DD base 50°F have accumulated. These degree days from petal fall will be included in the next summary table if you submit them to us. Without your actual petal fall date, NEWA estimates petal fall based on degree days accumulated from January first, which is likely to be inaccurate.

Rosy apple aphid
We are seeing a strong resurgence of rosy apple aphid this spring. If there are no longer any blooms on the trees, an insecticide such as Belay should be used over Avaunt for dual activity on PC and RAA. By early summer RAA will move to alternate hosts such as plantain and other broadleaf weeds.

Johnâ€s interview with Phil Schwallier
Many growers in western Wisconsin and eastern Minnesota have had some rain in the last week, while southeastern Wisconsin remains very dry. This rain has been helpful but need to consider this is not enough to replenish sub-soil moisture that has been depleted.  Therefore, if your orchard received 0.5” to 2” of rain in the last week, you are not out of the woods. The evapotranspiration rates of the trees are reaching 1.4” of water per week and growers that received rain benefited but have no reserve. A few rare locations received three or four inches of rain in May, but most growers have only accumulated one inch of rain in May.  Michigan is much like this, having only received one inch of rain this month.

Dr. Phil Schwallier of shared his opinion on these drought conditions with John:

• The dry sub soils should not impact return bloom initiation unless we see flagging or symptoms related to severe water stress in the trees. If you look at the trees in the afternoon and leaves are limp, this is an indication of water stress. If this continues through fruit bud formation, this will impact the number of buds that develop for next year.
• More importantly, an even bigger stress is how many fruit the trees set. Even with variable return bloom and freezes that damaged flowers, many growers do have a better fruit set than anticipated. More frozen blossoms set fruit than expected, which is good. If there is not enough rain to satisfy tree needs and trees are slightly over cropped, this will negatively affect fruit bud formation for 2021.

Thinning
As fruit begin to size, the influence of carbohydrate deficits and surpluses become even more significant. It is important to use the carbohydrate model and adjust rates of Fruitone (NAA) or MaxCel (6Ba) accordingly.  The model takes some of the guess work out of thinning by using the current weather forecast to determine if thinner rates should be increased, decreased, or applied at the standard rate. The model calculates the general carbohydrate balance, which has been found to correlate well with natural drop and decreasing tree sensitivity including sensitivity to chemical thinners. Cool, sunny periods of good carbohydrate supply leads to a natural drop and less response to thinners (increase thinner rate).

Cloudy, hot periods result in carbohydrate deficits and lead to stronger natural drop and stronger response to thinners (decrease thinner rate). The carbohydrate model needs to be consulted at the time of thinning to help determine rates. The grower needs to use their experience with thinning and adjust rates based on what they have applied in the past to the target variety and crop stage. This model does not tell you what product to use or what rate to apply but is particularly helpful when using MaxCel (6-BA) or Fruitone (NAA), that are dose dependent. Conversely, Sevin (carbaryl) is not dependent and will generally provide the same level of thinning regardless of rate. You can access the carbohydrate model from your local NEWA station.

When thinning with carbaryl: Remember that an application of carbaryl can be reactivated by light rain showers if rain is received within 48 – 72 hours of the carbaryl application. Carbaryl is not dose dependent and one pint per 100 gallons of water will work the same as one quart per 100 gallons of water. Carbaryl has never been a strong thinner and is a good at singluating or removing side blooms that are 2 – 3 mm smaller than king fruit, e.g., 10 mm lateral and 12- 14 mm king; carbaryl will remove some laterals.

If using NAA or 6BA avoid an adjuvant or acidifier or penetrant. Regardless of your carbaryl rate, the carbaryl should not impact of NAA.

 May 18^th Call Stream: CLICK HERE

Table 1. Degree days and ascospore maturity downloaded on 5/18/21 from Cornell NEWA system. Find your local station today: http://newa.cornell.edu.

Regional summary
Warming temperatures and increasing likelihood of rain across the region will bring with it increased risk of scab infections; the first signs of plum curculio activity and the start of codling moth monitoring. Fire blight risk is minimal for varieties at petal fall, but non-bearing trees or trees still in bloom will be at risk of fire blight infections, if the forecasted rain materializes.

Soil moisture management
Inadequate soil moisture still widespread, with all AppleTalk participants in areas classified by the National Weather Service as a “Moderate Drought”. John has observed soil temperatures around 69F at 7″ and this rapid warming of soil reflects its dryness. June beetles are emerging earlier than normal, reflecting very warm soil temperatures.

The importance of water trees now, before summer heat sets in cannot be understated. We have been getting by because the cool temperatures are keeping transpiration rates low. However, with warm weather comes increased transpiration. The goal should be to apply one inch of water per week (0.67gal. per sq. ft.) on all but semi-dwarf trees. That is approximately 6-gallons per week for a mature Bud9. It has been so dry that John has observed water from drip irrigation sucked out two feet away from the tree via capillary action. We should consider that 7 – 14-year-old Bud 9 trees still have a small root system and small amount of soil they can tap into for their moisture.

Diseases
Spring disease complex (apple scab, powdery mildew, cedar apple rust)
The warnings and forecast to be prepared for big scab infection period have been discussed in detail over the last month. As we near the end of primary scab season, keep in mind that mature inoculum will remain present until released during a rain. Some amount of rain is forecasted across the region and orchards should be receive protectant fungicides prior to this rain.

The need to apply a single site fungicide, e.g., strobilurin, sterol inhibitor or an SDHI, is largely dependent on your historical disease pressure from scab, powdery mildew, and cedar apple rust. The conditions over the next week remain excellent for the spread of powdery mildew and at the current temperatures, a wetting period of four hours is all that is needed for a cedar apple rust infection. Powdery mildew has been observed already in parts of western Wisconsin and southeastern Minnesota, likely a result from the first round of 80F weather we experienced two weeks ago.

It is also around the end of petal fall when black rot begins spreading its inoculum. Good captan coverage is important to stop fruit infections and if you have had black rot infections in the past, considering including a strobilurin, e.g., Flint or Sovran, in your tank mix.

Considering the severity of the forecasted infections, Organic growers should consider application of sulfur for powdery mildew and scab ahead of rain.

Fire blight
As blossoms begin to age and turn brown, their overall susceptibility to fire blight decreases. However, where bloom persists, this week will pose fire blight risk for trees with open blossoms. It has been a long fire blight season and is reflective of an extended bloom period.  We are in a situation where there are Zestar with 10mm on king fruit and other varieties with bloom still opening. Growers to the north (Lake City, Eau Claire, Minneapolis, or further north) will need to protect whole orchards/blocks still in full bloom. Growers in Lacrosse to Green Bay and further south into Illinois, will only need to spot spray. If you planted trees this spring, these may be opening into bloom over the next two weeks and as their blossoms open, fire blight risk will be dependent on rain fall.

If you are going to apply streptomycin, remember that Regulaid only needs to be applied once. If streptomycin plus Regulaid was already applied, the petals have already been penetrated with Regulaid, the second application a few days later does not need Regulaid.  However, late bloom that was not exposed to Regulaid, will still need this if you want to use the lower rate of streptomycin.

Once you are at or past petal fall and fruit is sizing to 5mm, streptomycin applications should cease. If you have established trees with a history of fire blight, Cueva and Double Nickel can be applied as a tank mix.  This tank mix has been found to stop the spread of existing fire blight infections and may be used preventatively at and after petal fall to help prevent shoot blight infections. Cueva is a copper and with any copper, there is always a risk of russeting. Supposedly, the combination of Cueva PLUS the Double Nickel is to have a reduced risk of russeting.

Insect management at petal fall
Codling moth
Many orchards in southern Wisconsin caught their first codling moth between May 11^th-14^th.  However, a flight one night does not necessarily constitute a biofix. The first codling moth (CM) capture has traditionally been around petal fall or 180 DD, base 50°F and most sites are between the 180 to 250 DD base 50°F from January 1^st; within the required-degree day accumulations needed prior to the first codling moth (CM) flight.

There is a reasonable probability that orchards to the north (Lacrosse, Chippewa Falls, Eau Claire, and possibly the southern end of the Twin Cities) could have a flight this week with the warmer weather. Codling moth traps should be checked nearly daily to establish the first CM flight. Codling moth biofix is marked by a significant biological event, or first sustained flight, where moths are captured multiple days in a row or exceed a threshold of five moths per trap per week. Once a biofix date is established, begin tracking degree-days (base 50°F) and monitor traps weekly. If you are calculating degree-days by hand, be aware that codling moth has a top developmental threshold of 86°F, which means all temperatures above 86°F should be counted as 86°F, e.g., a high of 95°F would be changed to 86°F degrees, if calculating by hand. Degree days are also available from your nearest NEWA station here, http://newa.cornell.edu/index.php?page=degree-days.

If mating disruption is used, hang at least one CM combo lure (CMDA) per block and at least two oriental fruit moth (OFM) traps per orchard. The CMDA lure will attract female and male CM moths. The Trecé Combo Meso boxes only cover half as many acres as the CM Meso box because there are two species being disrupted.

Codling moth fly between 6pm and 11pm when wind speeds are between three and five miles per hour and when temperatures are above 62°F, without rain. Assign the biofix date for the warmest, calmest night. When checking traps, fluttering CM had likely flown within the last 48 hours. Most female CM can live for seven to 14 days yet will mate and deposit the majority of eggs on the evening they emerge. Every day that a sexually viable female emerges and is not able to fly, egg fecundity is decreased by 20%.

Beware of the CM look alike! Proteoteras is genus of moths belonging to the family Tortricidae. Codling moths are also in this family, but belong to the genus Cydia, and have some similarities in appearance and can be confused with these moths. Proteoteras has a similar wingspan, but is slightly narrower and lacks the bronze coloring on the wing tips of CM. For photos of CM and two look-alikes visit: http://www.mda.state.mn.us/Global/MDADocs/pestsplants/applefieldguide/cm.aspx

Table 2. Codling moth lure lifespan for first and second generation flights.

¹ http://msue.anr.msu.edu/news/using_pheromone_traps_to_monitor_moth_activity_in_orchards1

² http://entomology.tfrec.wsu.edu/stableipm/WorkshopPDFs/cmmonitoring.pdf

³ No data was available on the lifespan during second generation, but we should presume decreased life of these pheromones based on average temperatures in July and August that have potential to decrease duration of pheromone release.

Plum curculio
The temperatures expected over the next week will likely trigger plum curculio migration from overwintering sites. One orchard in southern Wisconsin that has historically high pressure has reported some PC feeding injury but no oviposition injury.  Prioritize scouting varieties such as Zestar, Ida red, Paula red, Liberty, etc. that size first. This yearâ€s cool weather has likely prevented any significant movement of PC into the orchards, but the current weather now offers perfect conditions for PC to begin moving into the orchards and it is essential to scout the perimeter of the orchard and focus on historical hot spots and locations that have the largest fruits.

Plum curculio (PC) emergence begins between bloom and petal fall, and movement into the perimeter of orchards begins when temperatures are above 60°F. This is a gradual process and requires several days of warm weather. PC are primarily nocturnal, and the greatest amount of activity will occur when temperatures at night remain warm. The entire population does not migrate into the orchard at the same time and fruitlets become susceptible to PC egg-laying when they reach 5 mm. When PC first move into the orchard, they must feed and mate for a period of about seven days, before egg laying begins and the typical crescent-shaped scars appear.

Please make note of the 95% petal fall date and report back to us. Tracking degree days from petal fall may be used to predict when their emergence from overwintering sites ends, which occurs after 308 DD base 50°F have accumulated. These degree days from petal fall will be included in the next summary table if you submit them to us. Without your actual petal fall date, NEWA estimates petal fall based on degree days accumulated from January first, which is likely to be inaccurate.

Spraying perimeters more frequently is one option to reduce cover sprays. If PC injury is found past the perimeter, e.g., first four or five rows of trees, a full cover spray is recommended. In the past, many assume that thinning sprays with carbaryl will offer protection against PC. Thinning with carbaryl at one pint per acre delivers a half pound of actual carbaryl, whereas if carbaryl was used as an insecticide, this rate would be delivering two to four pounds of actual carbaryl per acre. Therefore, the rates used for thinning are not going to deliver insecticidal activity. Reducing rates of carbaryl may help lessen the impact on beneficial insects in the orchard.

Avaunt (indoxacarb) has been the most applied organophosphate alternative to manage PC. Many of the newer insecticides use a combination of contact mortality, systemic activity as an anti-feedant or ingestion, to manage PC. The neonicotinoids Actara (thiamethoxam), Assail (acetamiprid) and Belay (clothianidin) offer a few days of contact mortality and after several days the insecticide penetrates the fruit and acts as an anti-feedant and oviposition repellant. Exirel (cyantraniliprole), a diamide insecticide related to Altacor (chlorantraniliprole), may be used to manage PC and CM. It has similar activity to Avaunt, which requires ingestion.

Note: Belay is very toxic to beneficial insects and pollinators and will remain toxic to pollinators for more than five days after an application. It is critical to wait until bees are out of the orchard and there are zero blossoms left on the trees and minimal bloom in the groundcover before applying Belay.

To date, PyGanic (pyrethrum) continues to be the most effective insecticide for organic production. PyGanic is very short lived and very unstable when exposed to ultraviolet light.  This means that PyGanic should always be applied at night and typically only will last 12 to 24 hours, or less. Considering this, be vigilant with scouting and wait for the first signs of PC feeding or oviposition injury before making a spot spray or perimeter insecticide application (this advice could be headed by anyone that wants to move the needle on minimizing excess pesticide use).

Regarding perimeter sprays, it is common to see growers apply perimeter sprays anywhere from one to four rows deep.  Realistically, the perimeter is whatever width you can get away with while still having an effective treatment.  Growers with light PC pressure should consider spraying only one row.  If you have abandoned trees or heavy pressure, more rows should be sprayed. There is no “textbook” definition of what defines the perimeter.

Thinning
Preliminary observations suggest that fruit set generally looks better than expected, especially where freeze damage to blossoms was the primary issue rather than lack of return bloom. Early sizing cultivars in the most advanced orchards are nearing 10mm Kings now, although within the same orchards late blooming varieties still have fresh blossoms, so assess and thin accordingly. Once fruit size to 5mm, fruit are probably not falling off in next five to ten days. Fruitlets may stick and stems remain green for a week after petal-fall, before abscission proceeds, which means do not rush thinner applications until you’re certain what will size to the 5mm-7mm range. The weather in the three days after a thinner is applied is the most critical factor in its effectiveness, so except for the possible rains, the next seven days look excellent for thinning materials to be absorbed and metabolized.

Please see last weekâ€s AppleTalk notes for more links and in depth discussion on thinning using the carbohydrate model.