August 13 AppleTalk

AppleTalk Conference Call Summary
Tuesday, August 13, 2019, 8:00 – 9:00 AM

Presenter: John Aue, Threshold IPM
Moderator: Peter Werts, IPM Institute of North America; questions or comments,

August 13th Call Stream: CLICK HERE

Regional update 

Location Degree Days 8/13/2019 (Base 50°F) Petal Fall Date (NEWA) Total potential infection event hours, from petal fall CM Biofix (NEWA) Accumulated DD (Base 50°F) from CM biofix
Eau Claire, WI 1561 5/28/2019 278 6/8/2019 1245
Gays Mills, WI 1781 5/30/2019 242 6/6/2019 1409
Hastings, MN 1753 6/1/2019 130 6/7/2019 1397
Harvard (Royal Oak), IL 1741 5/23/2019 299 6/6/2019 1387
Lake City, MN 1756 6/1/2019 186 6/3/2019 1463
Mauston (Northwoods), WI 1724 6/1/2019 175 6/7/2019 1371
Mequon (Barthel), WI 1471 6/6/2019 138 6/15/2019 1142
Preston, MN 1679 5/31/2019 200 6/3/2019 1393
Rochester (Ela), WI 1602 5/23/2019 239 5/30/2019 1389
Trempealeau (Eckers), WI 1727 5/31/2019 228 6/6/2019 1393
Verona, WI 1773 5/30/2019 132 6/5/2019 1425
White Bear Lake, MN 1690 6/3/2019 136 6/8/2019 1338
Woodstock, IL 1892 5/26/2019 174 5/28/2019 1616

Table 1. Degree-day accumulation and leaf wetness hours to 8/13/2019.  Note: Degree days for codling moth are estimated by NEWA.  Actual dates must be entered by users and are not saved.  This year DD are as much as five days off grower-observed codling moth flights. *All degree days are calculated using a lower-temperature threshold or base temperature of 50°F.  *Leaf wetness events are periods of four or more hours.

Degree days and crop phenology
The accumulation of degree days over the growing season has widened the gap between insect phenology and tree phenology.  At petal fall both trees and insects were fourteen days behind typical phenology.  June weather brought lots of moisture, cooler temps and sunshine, and the trees grew quite well and caught up to the calendar.  However, the insects did not catch up and stayed behind the tree phenology during the month of June.  In July, the warm nights used up lots of sugars being produced by the trees, slowing their growth.  Now the trees are only a few days behind a normal range for harvest timing.  Varieties including Pristine, Ginger Gold, Zestar and Paula Red will probably be ready on time.  The current ten to fourteen-day forecast are showing very average August temperatures and trees will have good weather for coloring and sugar accumulation.  The insects are still behind and not likely to catch up.  Codling moth, lesser appleworm and obliquebanded leafroller, will continue to be active through August and into mid-September.

Second generation codling moth
Unlike in the spring, insecticides targeting second generation codling moth should not be delayed past 250-degree days (DD), base 50°F, from biofix, which takes 10-12 days of degree day accumulation.  We can delay in the spring, because adverse weather conditions and rain during the first flight often reduce the fecundity of female codling moths.  In late summer, we have excellent weather for codling moth mating and can expect a strong flight to require treatment at 250 DD, base 50°F.  Peak egg hatch for the generation will likely not occur until two to three weeks into August and right up until Labor Day.  On average, 650 DD accumulate during the month of August.

The treatment threshold is five moths per trap and after a biofix has been established, blocks that do not go over threshold may not require treatment.  This could be helpful as we near harvest and allow for spot treatments only of blocks which caught five moths or more in a weeks’ time.  While recording trap numbers are important, codling moth injury to fruit is also a great indicator of potential second-generation population presence in the orchard.

One larvicide application, no matter what product, will not carry you through August and into the first week of September especially if significant rain occurs.  If rain is forecasted, do not apply the highest rate of the material even if it has been three weeks since the last application.  Apply a low application and follow up if need be.  Keep in mind that Altacor (chlorantraniliprole) has a minimum interval of 10 days.  Excluding neonicotinoids, at this stage it is a good idea to incorporate a sticker with an insecticide application.  If growers are catching 5-15 moths, this is not a massive threat.  John considers catching 20+ moths to be more of a threat in terms of urgency to apply an insecticide.

Grower question: Can I use 10x Lures because L2 lures about to expire?
The L2 is a 10-12 week lure, and should be changed at 10-week intervals.  The plume begins to significantly drop off after 10 weeks.  The 10x lure lasts about two weeks and gives better idea of population dynamics, where mating disruption is being used.  If there is no mating disruption, then there is no advantage to using a 10x lure.  The preferred approach would be to use a 1x lure from Great Lakes IPM or Nutrien Ag Solutions.  This will last the rest of the season.  If new lures are hung, leave a few of the L2s in traps because it will verify how long the L2 seem to last.  A 10x lure should also not be used because the data from is not benchmarked against a threshold.  The 10x lure could theoretically catch many moths, but doesn’t reflect how they should be managed.

Obliquebanded and redbanded leafrollers
Grower question:  We are beginning to catch some OBLR and in the past it has not been a problem due to spraying for CM.  This year we are using mating disruption and do not need to spray for CM.  Should we use the same DD model for OBLR as we do with CM?

The second-generation of obliquebanded leafroller (OBLR) will hatch in late-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 OBLR’s growth and development is suspended until spring.

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, 42-43F.  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 10-14 days 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-days models for OBLR.  Utah suggests the first-generation flight occurs at 1025-1175 DD from January, 1 base 43F.  The flight for the second generation in Utah begins at 1100 and hatch begins at 1500.  Michigan suggests that OBLR biofix occurs around 900DD from January 1 base 43F.  The peak moth flight for second gen will happen at 2300 from the biofix date and egg hatch will start at 2750DD base 43F. 

This year our first-generation flight began between June 21 – June 26 in both southern Wisconsin and in the Upper Mississippi River Valley.  If we use June 26 as biofix, we have only accumulated 1460 DD from June 26 first gen biofix.  We are still 1000 DD base 43F from the peak of the second-generation flight and even further from second-generation egg hatch.  The second-generation hatch usually does not occur until the end of August and this year growers should expect OBLR to continue hatching into early September. 

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

Apple maggot
Apple maggot activity has been light throughout the region with captures continuing to occur in blocks with historic pressure.  Some orchards are reporting that they have yet to capture a fly all season.  In blocks with attractive varieties that are almost ripe, e.g., Redfree, or with hand thinned or hail damaged fruit baiting a few red spheres or putting out additional traps may have utility to make sure trap are not showing false negatives.  Baited traps do run the risk of drawing apple maggots in from outside the orchard.  The Wisconsin Pest Survey Bulletin from DATCP mentions how many AM growers are catching throughout the state. 

It is essential to continue monitoring for apple maggot through the end of August. At this juncture in the season we often ask, “How late do we need to monitor? If we catch AM on Labor Day weekend, do we need to spray?” Some literature suggests these late catches don’t need to be treated. An occasional catch is okay to ignore, but if you are getting multiple flies on multiple unbaited traps, you may need to apply an insecticide.

Assail (acetamiprid) is often a preferred insecticide for combined management of apple maggot and codling moth, especially late in the season.  If a different insecticide is being used for second-generation codling moth, then imidacloprid products may be used for apple maggot management.  The neonicotinoids have limited mortality on adult AM (two-to-three days) and increased mortality on eggs and their ability to hatch, plus repellency and avoidance of egg laying (up to 14 days).  Rainfall following an application will impact efficacy.  If Assail was applied with the dual purpose of controlling CM, reference John Wise’s article below to determine when to reapply.  A final AM application of the season should be a material that has efficacy on the adult fly as well, like Assail (acetamiprid), Imidan (phosmet) or carbaryl.  If a final product is applied that doesn’t have efficacy on adults, this will result in maggots hatching out when residue efficacy is diminishing and may lead to metabolic resistance. 

Note: Since neonicotinoids do not perform well against adult flies, trap captures will not be impacted by an application, whereas they would have been if a broad-spectrum material, e.g., Imidan (phosmet), were used.  If pressure is localized spot spraying may offer adequate control.  

Note: The fruit essence on baited traps is viable for one week and should be changed accordingly.

San Jose scale
The second generation of San Jose scale (SJS) crawlers are beginning.  If you have found SJS on fruit or young shoots continue to monitor for this pest.  As harvest begins, or while hand thinning, look for first generation adults (black cap stage) on fruit and continue to check scale tape on infested limbs for crawlers.  Fruit injury should serve as the canary and John recommends to continue maintaining tapes on branches regardless of what you plan to do management wise.  Second generation adults appear from late July through early September and the live young ‘crawlers’ from this generation can be found until a hard frost in the fall.  When checking tapes it is important to note that low trap captures do not reflect overall pressure, i.e., false negative, rather may indicate the beginning of the hatch.  Catches of 10-15 crawlers in a couple of days or 10 crawlers on one tape with zero on all other tapes, may warrant application.  See the article below for more information managing summer generation and be aware of PHIs when selecting insecticides.

Second Generation San Jose Scale Nymph Emergence & Peak Flight of Codling Moth & Continuing Larval Emergence, The Jentsch Lab, August 11 2017,

Woolly apple aphid
Reports of woolly apple aphid have been low this year.  If your orchard has some WAA, pay attention to the population size.  WAA populations that are not growing suggests there are good predators and parasites are keeping the colonies in check.  If a cover spray of carbaryl or Delegate are applied for apple maggot this could destroy the parasitic wasp that is working on WAA and could lead to a population explosion at harvest. If you blow off the fluff, you may find one of three things: A. a mass of purple aphids that are healthy and vibrant; B. black, mummified aphids that have been parasitized or; 3. minimal fluff and no aphids, which suggests predation by syrphid fly larva or another beneficial.

Brown marmorated stink bug status for 2019 harvest
This year BMSB populations have been rather light across the region, though populations generally do not increase until September.  This spring a few BMSB were captured in southern Wisconsin as they emerged from overwintering sites.  Mid-August is when we begin seeing BMSB again, but this year trap captures are low compared to what has been observed over the last three seasons.  We have seen BMSB populations steadily build in Dane County, and light populations in Rock, Walworth and Racine Counties.  The Minneapolis-metro region also has a BMSB population and orchards surrounding the Twin Cities should have BMSB traps up this fall.

In collaboration with the Wisconsin Department of Agriculture Trade and Consumer Protection, the IPM Institute has been monitoring brown marmorated stink bug (BMSB) in Wisconsin orchards since 2015. 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. Traps are now 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 won’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 MSU’s 2017 article,

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

Bitter rot
Bitter rot has been discussed extensively this season, even though incidences of the disease remain limited to date.  However, we are now entering the portion of the season where orchards with high inoculum are at a greater risk of infection.  Like sooty blotch and fly speck (SBFS), bitter rot has more genetic diversity than previously thought and while not completely immune to resistance, we currently are not very concerned about the current treatment programs resulting in fungicide resistance.

The visual symptoms of bitter appear as an orange, slimy mass that is almost salmon-colored.  Black rot and white rot make black fruiting bodies but do not make orange slime.  Bitter rot makes a sharper V-shape into the fruit, when cut in half, when compared to black and white rot.  This disease can cause problems on other fruit crops, weeds, lilac, trees and hedge rows, which suggests it has a wide host range beyond apples.  Spores likely enter orchards early in the season (June) through either fire blight infections or some other source.  For example, we know that SBFS come off brambles in the woods and hedge rows adjacent to orchards.

Fruit infected with bitter rot are often observed in groupings and clusters on several branches.  While bitter rot does not cause big cankers, it can infect quickly.  This suggests the source of inoculum is nearby, e.g., overwinter drop, mummied fruit, fire blight canker, rather than a pathogen that has spread via wind or rainstorms.  The pathogen can overwinter mummified in fallen fruit and in trees.  Rotten fruit tend not to decay very well on herbicide strips.  Fruitlets on the ground after hand thinning can also become infected and release spores.  Dead wood, e.g., infected by fire blight, can become colonized and sporulate by late-July.  In strawberry and blue berries, infections can happen in four-to-six hours during wetness, which is relatively fast for a fungus.

Even though the fungus requires vegetation to reproduce, the disease can appear after fruit have been harvested. Heat-stressed fruit also seems to be more susceptible.  When humidity is high, evapotranspiration is reduced, slowing fruit cooling.  Therefore, growers should ensure trees are well irrigated going into hot weather.

Bitter rot management

  • Applying an SDHI, Strobilurin and Captan are best options for bitter rot.
  • Phosphorous acid fungicides are not effective on bitter rot.
  • Organic options are limited.  Results from trials at UW completed by Patty McManus found that Liquid lime sulfur (LLS) had 9% injury, Serenade Optimum 10%, and the control had 7% bitter rot injury.  This suggests that none of these fungicides performed better than the control.
  • Cultural controls: Removing and mowing over is likely just fine, the key is getting fruit to decompose, which will destroy the inoculum.  A flail mower is likely to destroy the fruit better than a rotary mower.

Sooty blotch and flyspeck
Depending on your location and rainfall, SBFS infections have been variable.  Orchards that had SBFS problems last year were those that had high amounts of rain in September.  Pay attention to the weather and the last fungicide application.  The extended forecast is for dryer weather over the next few weeks.  Orchards that receive two to four inches of rain in early September, may need to treat late-harvested varieties for SBFS.

Bitter pit
Adapted from August 11, 2015, AppleTalk Conference Call with guest speaker Dr. Amaya Atucha, University of Wisconsin- Madison.

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

  • 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.
  • Keep soils adequately hydrated throughout the growing season.
  • 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.
  • 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.
  • 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

  • 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.
  • 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 also 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.


Determining fruit ripeness and harvest dates
Tracking days from full bloom can be used to plan the harvest of Paula Red and McIntosh. Paula Red harvest typically begins 100 days from full bloom and will can last two weeks. Picking for McIntosh starts 115 days from full bloom, with prime picking between 125 and 130 days. The goal is to have all McIntosh fruit harvested within 145 days of bloom.

Background color is primarily used to determine harvest of Zestar.  A light greenish background and brown seeds signals a ripe Zestar. There is not currently a good measurable sugar content, i.e., brix, so taste is helpful since it seems Zestar can go from starchy to sweet overnight.

When picking Honeycrisp growers look for a good yellowish green background color and red over color. On some sites this color never develops and the amount of red can depend on the strain of Honeycrisp. Most growers do two to three picks of Honeycrisp. The first pick is usually set aside for storage or late season sales and the following two are sold as soon as possible since over mature Honeycrisp do not store well. In some scenarios the third pick will invariably end up as cider.

When using Extension recommendations for starch-iodine tests, brix, or pressure always consider your orchards unique site-specific parameters and expect some variation between orchards and regions. Use the available tools to gather and generate data and determine what parameters work best for your operation. Harvest maturity equipment can be purchased from Peach Ridge Orchard Supply,!/Maturity/c/12544202/offset=0&sort=normal

Food Safety Modernization Act Training
Thursday, August 22
1-5 p.m.
Bushel and a Peck Orchard and Market
18444 Cty Rd OO
Chippewa Falls, WI 54729

Thursday, September 19
1-4:30 p.m.
Sully’s Produce
7054 Cty Rd C
Sturgeon Bay, WI 54235

Both events are free but they ask that you register online prior to the event: 

More information can be found on that website as well. If you would like to schedule an On-Farm Readiness Review at your farm, on that website there is a link called “On-Farm Readiness Review” on the left hand sidebar that will take you to a form to fill out. I’m not sure their state-wide schedule, but if you are in the Door County region, I was told that they might have openings on September 16 or 18th. 

Pesticide-residue testing for fruit
Residue testing is expensive and commonly completed by growers who must meet Maximum Residue Limits for export markets.  Residue testing is not necessary for fruit sold domestically, but growers interested in this may look for more information through the following labs:

IEH Laboratories & Consulting Group/ Environmental Micro Analysis Inc.
Woodland, CA

Pacific Agricultural Laboratory
Sherwood, OR

Anresco Laboratories
San Francisco, CA

SCS Global Services
East Bay, CA