July 21, AppleTalk Conference Call

AppleTalk Conference Call Summary
Tuesday, July 21, 2015, 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 21st Call download: Click Here

Second generation codling moth
Does a delayed 1st generation biofix mean a delayed 2nd generation biofix?  What are some tips to determine the start of second generation?
A delayed first generation codling moth (CM) biofix does not suggest a delayed second generation biofix.  The start of first generation CM emergence was scattered due to poor weather, e.g., cool temperatures, rain, and establishing a firm biofix was difficult.  Rather than targeting the first larvicide application 250 degree days (DD) from a biofix, Larry Gut, Michigan State University, recommends to time a larvicide based on a significant biological event, i.e., ‘cohort’, or when traps exceed a determined treatment threshold.

During second generation the same principal can be used to time the first larvicide application.  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 first generation biofix.

How should we respond and adjust to second generation management if we find injury?
High trap captures during second generation may indicate that damage may have occurred during first generation.  Injury can be caused by larvae not being exposed to a lethal dose of insecticide, which can result from poor coverage, wash-off, or developing resistance to the class of insecticide used for managing first generation.  It is difficult to provide a definitive answer which factor resulted in damage.  Note: Mating disruption, in addition to a larvacide, will significantly help reduce the development of resistance.

Use the following procedure to assess CM damage.  Note: It is ineffective to randomly sample for damage.

  1. Go to the area of orchard where trap counts were the highest.
  2. Scout cultivar with the heaviest fruit set or most woody growth; chances for reduced insecticide coverage in these areas are likely. If the block is on the perimeter of woods, look for damage along the edges since females are most likely to stop as soon as viable fruit is present.  High trap captures further to the interior of the block, e.g., 200-300 feet, are likely male moths.

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

How do we dove tail 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 larvicide if a neonicotinoid was applied for plum curculio during first generation.

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 life span.
  • Eggs hatch two to ten days after egg laying. Assail (acetamiprid) and imidacloprids 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.

For additional information on AM biology visit: http://www.nysipm.cornell.edu/factsheets/treefruit/pests/am/am.asp

Regional comparison of apple maggot pressure
In the upper Mississippi River Valley where growers received significant hail, AM were beginning to be caught on red ball traps by July 13.  Trap captures have been sustained since the first capture with moderate to high numbers being caught on unbaited, i.e., seven AM, and baited, i.e., 16 AM, traps.  Trap captures have been higher than in the past which may show the attractiveness of volatiles, i.e., ethylene, being produced by the damaged apples as they continue to ripen.  It is important to note that apple maggot represent a fraction of the “fruit flies” that are potentially coming into the orchard. Additional flies in the genus Rhagoletis and Drosophila can inflict similar damage to hail injured fruit.

In areas where growers did not receive hail, or hail was less severe, AM captures have been low, with the majority of traps not catching any flies and few traps catching 1-3 flies on unbaited red ball traps by the end of last week.  Overall the locations of trap captures have been sporadic and not entirely dependent on location of early season varieties or past hotspots.  The 7/10” of an inch of rainfall on Thursday, July 16th, may have spurred emergence in this area.

As a comparison, in 2014, AM emergence started the last week of July in this region; except for one site that caught an AM on July 10.

Washed off, now what?
The rain-fast characteristics of neonicotinoids is low to moderate, ≤ 70% to ≤ 50% of residue is washed off following 0.5 to 2 inches of rain, systemic residue will remain in the fruit tissue for ten days following an application.  The lethal residue has the ability to control the AM larvae when it first hatches out.  If the insecticide kills the larvae at this time, no injury will be found.  Following one inch of rain available insecticide residue will not control CM.

Note: Thresholds for unbaited red spheres is an average of 1 AM per trap per ten acres; three traps per ten acres is the minimum recommended trap density.

Secondary-pest headaches
Japanese beetle
A new strain of Bt (Bacillus thuringiensis) that can be used in organic and conventional orchards for control of Japanese beetle has been registered in Wisconsin. For more information: Phyllom BioProducts, beetleGONE!

Aphids and San Jose scale
San Jose scale and aphids can also be managed by neonicotinoids.  Application timing is important when targeting these pests.  It is recommended to scout and read product label before making application.

Summer disease and secondary scab: It ain’t over yet!
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 russeting.