August 2, AppleTalk Conference Call

AppleTalk Conference Call Summary
Tuesday, August 2, 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

August 2nd call download: Click Here

Stink bugs
August is typically when we begin to see feeding damage from adult stink bugs. We are not currently anticipating large numbers this year since we did not see many egg masses or nymphs during the early part of the season. Extensive research has not been completed on stink bugs and most available research is on management of the invasive brown marmorated stink bug (BMSB) This research is not as robust as many of our other direct fruit pest since they poised little threat to the crop when many of the broad spectrum insecticides, e.g., organophosphate, pyrethroids, and carbamates, were the mainstay of growers spray program.

When assessing damage at harvest it can be easy to confuse stink bug injury with that of other insect pests, e.g., apple curculio, plum curculio, tarnished plant bug, spring lepidoptera, or from mechanical damage, hail, bitter pit or cork spot. See pages 3, 15, 16, 17, and 26 of the attached presentation “What do we know about injury, monitoring and management of stink bugs in apples?” and the following link to see injury characteristic of stink bug and damage look-a-likes. It is important to note that there is no such thing as fresh stink bug injury, since it may take up to three weeks from feeding for visible symptoms to develop.

What do we know about injury, monitoring and management of stink bugs in apples?,
http://www.ecofruit.wisc.edu/appletalk/wp-content/uploads/sites/343/2012/articles/ShortandHogmire_stinkbugpresentation.pdf
– See pages 3, 15, 16, 17, and 26

BMSB Update: Assessing Fruit Damage at Harvest. Is it Hail, Bitter Pit, Apple Maggot or Stink Bug?
http://blogs.cornell.edu/jentsch/2014/09/18/bmsb-update-assessing-fruit-damage-at-harvest-is-it-hail-bitter-pit-apple-maggot-or-stink-bug/

Field Guide to Stink Bugs of Agricultural Importance in the United States,
https://pubs.ext.vt.edu/444/444-356/444-356_pdf.pdf

Brown marmorated stink bug monitoring update in WI
With funding from the Wisconsin Apple Growers Association, the WI Department of Agriculture, Trade and Consumer Protection, the University of Wisconsin and the IPM Institute have been maintaining statewide monitoring program for BMSB. Traps are located at orchards in Madison and throughout southwestern and southeastern Wisconsin and one site in northern Illinois. One trap in Madison recently caught BMSB nymphs.

There is yet to be an official confirmation of BMSB injury in any fruit or agronomic crop in Wisconsin and we are hopeful BMSB will not be a problem this year, but are confident that resident populations exist in pockets of Dane County WI. Established populations in other areas of Wisconsin have not been confirmed. To learn about all things BMSB visit www.stopbmsb.org.

Late season codling moth management
Continue to monitor pheromone traps to time insecticides applications. If traps do not exceed threshold an insecticide application is not necessary. Spot spraying blocks where traps exceed threshold may be a good option to avoid early varieties and pre-harvest intervals. If larvae are in fruit following harvest, damage can continue to occur in storage; larvae may emerge from fruit. Continue to monitor and consider treatment for other direct fruit pests, e.g., apple maggot, lesser apple worm, obliquebanded leafroller, at this time.

While scouting and assessing injury, most injury that is easily observed needs to be at a 1% presence or greater, to be easily detected. Over the years, John has assumed that since he never saw codling moth (CM) damaged apples the CM were coming in from the outside of the orchard. More recently he believes the orchards may house small resident populations. A grower can use the following technique to help assess the next season’s pressure by assessing CM damage at harvest.

1) Determine number of apples with CM damage out of total apples inspected and calculate percent injury.
Example (following italicized points below): 1 out of 500 apples has CM damage (0.2% injury)
2) Determine the total per acre.
100 apples per bushel x 500 bushel per acre = 50,000 apples per acre
3) Multiple total yield by percent injury.
50,000 apples per acre x 0.2% injury = 100 moths per acre
4) Assume that half of the moths per acre are male and that these will be caught during the first generation, the following season.
100 moths per acre/ 2 = 50 male moths. This suggest that a total of 50 male CM can be caught per generation per trap, and percent injury would likely be below 0.2%, or a detectable level.

If 250 moths are caught per generation, or an average of 50 per week, there should be visible damage. If no damage is found at harvest or if it is less than 1%, these moths are likely coming from outside of the orchard. Codling moth trap counts can also help determine why a certain area of the orchard may be catching more moths than others, such as, heavier set varieties or trees with dense canopies where coverage is poor.

Obliquebanded leafroller management
The second generation of obliquebanded leafroller (OBLR) will begin to hatch in August. 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 (acetamiprid), Admire Pro (imidacloprid), do not. 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. Two traps per 20 acres is adequate to determine where treating is necessary.

New success with woolly apple aphid management
John first witnessed treatable populations of woolly apple aphids (WAA) in the early 2000’s. Provado (imidacloprid) was the primary insecticide used because of its short pre-harvest interval and since it was the first imidacloprid registered in tree fruit. Up to that point, growers had not been using it much because it was only effective on leafhoppers, leaf miners and aphids, and was very expensive. Currently there are many generics and it has become one of the cheapest insecticides we can apply. Frequent applications of the newer material is no longer providing adequate management of WAA, and resistance is likely suspected.

The neonicotinoid, Actara (thiamethoxam) plus a penetrant was recently used by a grower with a serious WAA infestation and good control was achieved. This is a good example that resistance does not necessarily apply to a whole class of insecticides, i.e., neonicotinoids, rather just within the particular active ingredient.

Note: WAA colonies are not likely a concern if populations are small and studied with black parasitized aphids.

John would like to use last call as roundtable Q&A session

Pre-harvest intervals
080216 call