July 26, AppleTalk Conference Call

AppleTalk Conference Call Summary
Tuesday, July 26, 2016, 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 26th call download: Click Here

Question and answer with Sara Ecker, Ecker’s Apple Farm, on managing apple maggot in organic and IPM blocks with reduced-risk insecticides
Ecker’s Apple Farm has a one acre, experimental-organic block that is situated above their primary acres that are managed under an IPM program which does not include applications of organophosphates or synthetic pyrethroids.  Monitoring and management strategies differ between the two areas, and are continually being refined to achieve increased control of insect pests and diseases.  Sara’s strategies to manage apple maggot (AM) in the organic block have been to deploy red ball traps by July 1 used for trap out and use three traps in the block to monitor pressure.  Traps are placed in every few trees along the wooded borders to achieve some level of trap out.  The principal method to manage apple maggot includes two applications of PyGanic (pyrethrins), in addition to trap out.  The Pyganic also helps suppress populations of Japanese beetle.  One application of PyGanic included sugar, a phagostimulant that can increase consumption of insecticides by AM and other species, such as, spotted wing drosophila.  Sara is planning to apply Entrust (spinosad) for late season AM and codling moth (CM).  Surround (kaolin) is used for early season plum curculio management, but is avoided for use against AM because of difficulty removing the Surround residue from fruit and pack line at harvest.  Mating disruption and granulosis virus are the primary tools used for codling moth management.  Two applications of virus were made during first generation, and no damage has been found.  In spring 2017, wild hosts will be removed from surrounding woodlots to reduce pest immigration and disease inoculum.

Acres managed using conventional insecticides have two AM traps per block, one trap along the perimeter and one located on the interior.  This season, pressure has been steady along the perimeter and no AM have been captured by the interior traps.  Two applications of Assail (acetamiprid) have been used, one as a border and one as a full cover for AM, San Jose scale and Japanese beetle.  Delegate (spinetoram), plus sugar, was applied as a border spray to offer a break in the back-to-back neonicotinoid applications.  Delegate is labeled as suppression only for AM, and inhibits oviposition and has some toxicity against adult females.  Sara plans to deploy more AM traps in this block to confirm that flies are not moving beyond the perimeter.

What opportunities do we have to combine CM and AM management?
Growers applying Altacor (chlorantraniliprole) for second generation CM can choose to apply Exirel (cyantraniliprole) for CM control and apple maggot (AM) suppression.  Do not apply Exirel if Altacor was used to treat first generation CM.  Growers can also choose to tank mix an imidacloprid, e.g., Alias, Montana, Wrangler, with a codling moth insecticide for AM and CM control.  Do not apply imidacloprid without a codling moth larvacide if a neonicotinoid applied for plum curculio overlapped with first generation codling moth.

 Apple maggot quick facts

  • Newly emerged adults are sexually immature and feed on aphid honey dew seven to ten days after emergence. Yellow sticky boards can be used at this time to capture newly emerged flies.
  • Females can lay up to 300 eggs in a 30-day lifespan.
  • Eggs hatch two to ten days after egg laying. Assail (acetamiprid) and imidacloprid penetrate the cuticle of the apple quickly (2-3 days) and have the ability to control the AM larvae when they first hatch.
  • AM pupae can remain in the soil for two years before emerging as adults.

 Notes on imidacloprid

  • Overuse could increase risk of pests with multiple generations developing resistance, e.g., San Jose scale, white apple leafhopper, woolly apple aphid. Apply spot sprays or alternate-row-middle applications and only use as full cover when necessary.
  • Imidacloprid is effective on insects with piercing, sucking mouth parts. These materials translocate readily into plant tissue and the cuticle of fruit flesh. Apple maggot larvae are impacted in this manner, may not offer effective control if it is not working on adults.
  • Surface v. systemic wash off rates vary and surface residues of imidacloprid are susceptible to wash off following one inch of rain, whereas the systemic residue may remain within the plant tissue.
  • All neonicotinoids have limited lethal action on adult apple maggots, but provide strong curative activity on eggs and larvae. It is recommended to apply neonicotinoids as full cover spray to blocks that exceed threshold.  Alternate-row-middle applications will not provide adequate control. For more information visit: http://msue.anr.msu.edu/news/managing_apple_maggots_with_insecticides

Wash off and reapplication
Understanding wash-off rates are critical for timing the reapplication of insecticides.  Current research from John Wise, Michigan State University, shows that application rates do not influence the rain-fast characteristics of insecticides after two inches of rain.  When determining application rate consider CM pressure and weather forecast; increase application rates when CM pressure is high, e.g., 30 CM/trap/week, decrease rates if CM pressure is low, e.g., 5-15 moths/trap/week, and rain is in the forecast.  No insecticide can be exposed to two inches of rain and effectively control CM.  IMPORTANT: Read product label to determine minimum application interval and maximum permitted applications per season.  Read John Wise’s full article on rain-fast characteristics of insecticides, http://msue.anr.msu.edu/news/rainfast_characteristics_of_insecticides_on_fruit

What can go wrong now?
Codling moth
Most growers had a second generation codling moth biofix sometime in the last ten days.  Considering the timing and duration of this flight, the second generation could last into the third week of August.  This means that we could have codling moth pressure that overlaps with harvest, or at the very least, pre-harvest intervals which overlap with harvest activities.

Unlike in the spring, insecticides targeting second generation codling moth should not be delayed past 250 degree days (DD), base 50°F, from biofix.  We are able to 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

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.

European red mites (ERM), two spotted spider mites (TSSM) and apple rust mites (ARM) are all species that can become problematic in our orchards.  This year we have not seen as many TSSM or ARM, but ERM have been quite active in many orchards.  The Cornell mite sampling threshold increases to an average of 7.5 motile mites per leaf from August 1 to August 15.  Treatments are typically not applied to treat mites after August 15th.  Scouting activities are seeing more predators and mite populations beginning to be on the decline.  A challenge with using thresholds is often they don’t account for “mite days”.  Under this scenario, we could still have economic injury even when mites are under threshold.  This occurs when long periods of feeding still result in bronzing.  If we are seeing visual damage to leaves from mites and at 5/leaf or 7.5/leaf, and no predators, mites likely over threshold.  5/mites will not likely show damage if they just showed up, but if they have been busy since petal fall, bronzing injury is likely to be present.

Please remember that some of the miticides have a longer pre-harvest interval, especially products like Nexter (pyridaben) which can be applied as a rescue treatment.  Most other miticides have a 7-day PHI.  Rotating modes of action is critical when treating mites and this year we have seen several examples of miticide failures with newer products like Nealta.  Therefore Don’t feel pressure to buy a miticide from a distributor if their options are too limited and will not allow you to rotate modes of action, e.g., used same miticide last year or earlier this year.

Summer diseases and scab
The first sooty blotch and fly speck symptoms have been observed in orchards in southern Wisconsin.  If apples are going to not be harvested until the middle of October, there is plenty of opportunity for the sooty blotch and flyspeck fungi to infect these fruit.  During this period of hot weather we experienced, scab often shuts down and becomes less active, fruit of certain cultivars also become slightly more resistant to scab by this time of the year.  We should remember that, scab can become reactivated when cooler and wet weather returns cause additional fruit infections late in the season.

Captan (captan) is the primary fungicide for managing secondary scab infections, summer disease and fruit rots at this time in the season.  It is recommended to calculate the total amount of captan that you have applied this season and compare it to the maximum allotted amount per acre, e.g., do not apply more than 40.0 pounds of Captan 80 WDG per acre per crop cycle.  If scab is present in the orchard using a higher label rate is ideal, yet if you are approaching the seasonal maximum it is better to use a lower rate and more applications rather than leaving fruit unprotected.  Captan can eradicate many of the spore producing lesions, reducing the risk of new infections.  For eradication purposes, high rates applied as dilute solution for good coverage in temperatures over 80°F are most effective.

The rule of thumb for how long captan will remain effective is 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.  Note: The application of an SI or QoI (strobilurin), e.g., Flint (trifloxystrobin) or Pristine (boscalid, pyraclostrobin), fungicide on active secondary scab lesions scab greatly increases the chance of resistance developing to those compounds.  If these materials are used tank-mix with a full rate of captan.

The best organic eradicant/protectant is lime sulfur.  Low rates, and limited applications of lime sulfur can reduce tree stress and fruit russetting.

Fruit rots
The weather has been excellent for the development of fruit rots, e.g., bitter rot.  We have not currently seen any bitter rot infections, but incidence can is expected to increase especially on sun damage fruit of susceptible cultivars.  Bitter rot can spread from one fruit to the next and Honeycrisp seems to be somewhat susceptible to fruit rots.  A quick option is to simply pick off fruit that appears with possible infections.  Fungicides including Captan tank mixed with strobilurins or DMI fungicides will provide protection against bitter rot.

Blossom-end rot and moldy core
At harvest we occasionally find fruit that have mold growing in the core or small lesions around the calyx end of the fruit.  This is more often a problem with varieties that don’t allow the calyx end of the fruit to close up and infections actually occur at petal fall.  If you see these lesions, not to worry, while unsightly, they are not going to spread to any other fruit.

Additional insect pests

  • Occasionally tarnished plant bug can become active again late in the season, but generally does not cause economic injury. A great majority of the injury observed on fruit at harvest was caused by feeding beginning at pink and ending at petal fall.
  • Stink bug activity typically increases in August and this year there have not been many egg masses, nymphs or adults found on the crop. Please remember there are both native stink bug species and the invasive brown marmorated stink bug.  To date, no BMSB’s have been caught in any of the traps at orchards participating in our statewide monitoring program.  You can learn more about BMSB at stopbmsb.org.
  • The second flight of obliquebanded leafroller (OBLR) and third flight of redbanded leafroller (RBLR) are beginning in most regions. At this time feeding injury from RBLR are of less concern, but OBLR larvae feeding can be quite problematic on fruit as harvest nears, and insecticide applications targeting CM cease.  Continue to monitor growing terminals and fruit for feeding injury.