July 11, AppleTalk Conference Call

AppleTalk Conference Call Summary
Tuesday, July 11 2017, 8:00 – 9:00 AM
Presenter: John Aue, Threshold IPM
Moderator: Peter Werts, IPM Institute of North America; questions or comments, pwerts@ipminstitute.org

July 11th Call Stream: CLICK HERE


Station Location CM Biofix Date DD Accumulation Base 50°F

Woodstock, IL

5/24/2017 879

Verona, WI



Gays Mills, WI



La Crescent, MN



Lake City, MN 6/6/2017




Petal Fall Date

LWH from PF

Woodstock, IL



Poplar Grove, IL



Verona, WI



Gays Mills, WI



La Crescent, MN



Elgin, MN



Lake City, MN



Hastings, MN




Wisconsin Apple Growers Association – 2017 Summer Field Day
Tuesday, July 18 2017 – Green’s Pleasant Springs Orchard, Stoughton WI


Spotted wing drosophila
The article written by Mark Longstroth should be read by all fruit growers as a primer on what an emerging major pest can mean to farm survivability.  The Jentsch Lab post has a review of approaches to spotted wing drosophila management; it’s a nice follow up for growers with soft fruit.

Plan to change when dealing with spotted wing Drosophila, June 28 2017, Mark Longstroth, MSU Extension, http://msue.anr.msu.edu/news/plan_to_change_when_dealing_with_spotted_wing_drosophila

Spotted Wing Drosophila in Hudson Valley Sweet Cherry, July 6 2017, The Jentsch Lab, https://blogs.cornell.edu/jentsch/2017/07/06/spotted-wing-drosophila-in-hudson-valley-sweet-cherry-july-7th/

Summer disease management
Many regions have exceeded the 175 LWH from petal fall threshold and should have already or soon will need to make fungicide applications to manage the sooty blotch and flyspeck (SBFS) complex.  We now know that relative humidity (RH) is just as important as a predictor as leaf wetness hours (LWH) to predict infection periods.  Dr. McManus 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.  Regardless of the new research into using RH, Dr. McManus recommends using LWH because the instruments are more precise.  It is important to place the leaf wetness plates within the canopy to accurately record LWH.

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 14 days of weathering, higher rates may offer added protection.  In addition to captan and Topsin (thiophanate-methyl), the SDHI, strobilurin and DMI fungicides may be used for SBFS.  Do not use any fungicide class that you rely on for primary scab season.  When apple scab is not a problem, these can be attractive because of their ability to also manage black rot and bitter rot.  The potential for SBFS to develop resistance to these single-site fungicides is minimal because new spores are coming in from outside the orchard and disease is really a complex of more than 50 different pathogens.  If apple scab is present, it is essential to avoid exposing these single-site fungicides to secondary scab populations.  If you find yourself in this second scenario this season, it is recommended to apply high rate of captan or captan + Topsin.  Single-site fungicides can still be used to target varieties or blocks without scab, e.g., Honeycrisp, but avoid the McIntosh, Empire and other scab-prone varieties.

If you are worried about fruit rots, and do not want to apply high rates of captan later in the season, you can use targeted sprays of signal sites for bitter rot management, e.g., Honeycrisp.

See June 20th call summary for additional discussion http://www.ecofruit.wisc.edu/appletalk/june-20-appletalk-conference-call/

Fruit rot management
Characteristics of bitter rot, fruit:

  • Most orchards with bitter rot have their own strain or collection of fungi which make up the complex we manage, which can start to cause resistance problems.
  • Generally takes several weeks following infection before symptoms develop, may become visible before other rots.
  • Symptoms first appear as small, light-brown, circular spots. Many spots per fruit may be found.
  • Under high temperatures initial lesions may rapidly enlarge and change to dark brown in color.
  • 1/8 to 1/4 inch in diameter lesions are distinctly sunken or saucer shaped.
  • When lesions reach 1/2 inch in diameter, small, black fruiting bodies appear in the sunken lesion. Fruit bodies may be arranged in concentric rings.
  • Fruiting bodies will begin to ooze a gelatinous, salmon-pink mass of spores, which is washed by rains onto other fruit.
  • Beneath the surface of the spot, the flesh is light brown and watery in a cone or V-shaped area, with the small end of the cone toward the fruit center.
  • Cankers can form on vegetative tissue, but are rare.

Characteristics of black rot, fruit:

  • Black rot infections on fruit usually appears at the calyx end and can originate at any wound that penetrates the epidermis, e.g., insect or hail injury.
  • 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. Lesions are usually amorphous. The flesh of the decayed area remains firm and leathery.  Fruiting bodies will appear on the surface of the rotted tissue.
  • Fungicides that will offer protection against fruit rots include captan, strobilurins, e.g., Pristine (boscalid, pyraclostrobin) and Flint (trifloxystrobin), and Topsin. 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.

For more information on fruit rot management read: The Bitter Truth – New Considerations for Controlling Bitter Rot on Apples, pg 4-6, Dave Rosenberger, Scaffolds Fruit Journal, July 10 2017, http://www.scaffolds.entomology.cornell.edu/2017/SCAFFOLDS-7-10-17.pdf

Second generation codling moth
Second generation codling moth (CM) flights have started in some areas.  A good indicator that second generation has begun is if trap captures have been low and begin to increase or exceed threshold 900 to 1150 DD from the beginning of first generation flights.  If there was successful egg laying completed in early to mid-May the flight of second generation is likely to begin now.  If CM pressure comes from partially outside the orchard, using the earliest flight, e.g., pre-biofix, is important when determining the start of second generation.  If CM pressure coming from resident populations within the orchard using first generation biofix will suffice.

If trap density is adequate, e.g., one trap per 2.5 acres in non-mating disruption blocks, we often have the ability to spot spray for second generation CM.  Whereas for first generation we tend not to want to risk doing a partial spray.  When selecting insecticides to control second generation it is critical to rotate mode of action.  For example, if a neonicotinoid, e.g., Belay (clothianidin), was used to treat plum curculio and the treatment overlapped with first generation CM management, use caution about exposing second generation CM to neonicotinoids alone or without an effective tank-mix partner, e.g., Altacor (chlorantraniliprole).  The need to control second generation can often be variable and dependent on how well first generation was controlled and/or pressure populations in neighboring wild trees.

We have been fortunate in our region to not have CM develop resistance to our new insecticide chemistries.  Resistance concerns do increase during second generation CM management because extended spray intervals result in pesticide degradation and wash off, which ultimately expose CM to sub-lethal doses of the insecticide.  If we rotate often between generations, the concern about weathering out insecticide is less of a concern.  Therefore it is important to rotate with other modes of action between generations and seasons.  For example, how many years in a row have you been using the same product for second generation?  This resistance risk is less of a concern when we are using mating disruption. If you want to apply Assail (acetamiprid) or Exirel (cyantraniliprole) for second generation CM but used one of these products for plum curculio earlier this season, you can mitigate resistance by tank mixing two materials with efficacy against CM, e.g., CM virus or Delegate (spinetoram), then it is ok.

Apple maggot
Red spheres should be up in all orchards across the region.  Apple maggot (AM) emergence is often spotty in late June and early July, and reports from growers confirm this with low and isolated trap captures.  We expect trap captures to increase as we move into mid-July and through the month of August.  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 we 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 tax 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, but 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.

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 you are catching maggot flies on red spheres, they are laying eggs and there is no safe interval to wait to spray.  In practice, the numbers we are catching are fairly low density and if most traps are zero and only catching a few, you are probably okay, however, as numbers increase, the urgency to spray increases.  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.

Japanese beetle
Japanese beetle (JPB) is moving into the areas of our region that have had historic pressure, e.g., Eau Claire, Chippewa Falls, southeast Wisconsin and northern Illinois.  Insecticide options for this pest are rather limited.  Neonicotinoids, e.g., Assail, will offer good repellency if applied before large aggregations of JPB begin to appear.  If populations are large, applying a “knock-down” or contact insecticide, e.g., organophosphate or PyGanic (pyrethrins), may offer good control.  This year John has found that a combination of 1 – 2 lb. of Imidan tank mixed with a neonicotinoid may give us much better management of this pest.  Carbamates, e.g., Carbaryl, also work, but are much more disruptive to biological controls and other natural enemies that may be active in the orchard.  If you are avoiding organophosphates, carbamates or pyrethroids, then it is very critical to make an application of a neonicotinoid at the first sign of their feeding injury and before the aggregations appear.  If imidacloprid products are applied for AM, e.g., Wrangler, Alias, Montana, these should also offer some repellency and anti-feeding properties for Japanese beetle.

Organic producers have the option of applying neem (azadirachtin) oil products, e.g., Azadirect, Neemix, Trilogy, or PyGanic.  It is important to be aware that a botanical insecticide such as neem may be phytotoxic if tank mixed with other pesticides.  Additionally, several years ago a new product called beetleGONE! (Bacillus thuringiensis galleriae) was introduced to the market.  Trials done at UW Madison on roses found that beetleGONE! performed decently on roses.  When we looked into pricing last year, it was still quite expensive, but worth investigating and organic producers should keep on their radar.