August 1, AppleTalk Conference Call

AppleTalk Conference Call Summary
Tuesday, August 1 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

August 1st Call Stream: CLICK HERE

How long will an application of Assail last for apple maggot?
Assail (acetamiprid) has limited mortality on adult apple maggot (2-3 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 and if Assail was applied with the duel purpose of controlling codling moth reference John Wise’s article below to determine when to reapply. Note: Since neonicotinoids do not perform well against the adult flies, trap captures will not be impacted by an applications, whereas they would have been if a broad-spectrum material, e.g., Imidan (phosmet), were used.

Rainfast characteristics of insecticides on fruit, John Wise, Michigan State University Extension, http://msue.anr.msu.edu/news/rainfast_characteristics_of_insecticides_on_fruit

Native 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 native stink bugs, e.g., green stink bug, dusky stink bug, one-spotted stink bug, spined soldier bug, 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, 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 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. BMSB was first trapped in a crop in WI in 2016 and as of spring 2017 BMSB has been confirmed in 14 counties, with the highest densities being found around Dane County WI. So far this year adult BMSB have been trapped in apples and urban areas. None of the monitoring traps have 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. 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
Apples may be a week early, but pest activity for codling moth (CM) and obliquebanded leafroller (OBLR) may be going late into the end of August. It is recommended to continue to monitoring pheromone traps through early September 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.

Codling moth activity can change dramatically from one generation to the next. A small percentage of fruit infested during first generation can translate to significant damage during second generation. Now is an excellent time to assess where we are regarding first generation control. Fruit colors up a lot in August and when it colors prematurely, it is pretty easy to pick out damaged apples. Even something like McIntosh will ripen sooner. Another great place to look for codling moth injury is areas where two apples are growing together from the same cluster. While scouting and assessing injury, most injury that is easily observed needs to be at a 1% presence or greater, to be easily detected.

Following from August 2 2016, AppleTalk Conference Call:
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 and can continue through Labor Day. 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 larvacides, e.g., Delegate (spinetoram), Altacor (chlorantraniliprole), will control these larvae, whereas the neonicotinoids, e.g., Assail, 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. A mistake with OBLR may discount an apple from US Fancy grade, but is not usually a real problem when selling the fruit since the injury is so tiny and there is no worm in the apple. Two traps per 20 acres is adequate to determine where treating is necessary.

Dogwood borer
Adult dogwood borer (DWB) are continuing to fly and over the last month it has become very difficult to find active larvae in the trunks. Flights in southern and southeastern WI has been lower, i.e., 5-10, moths/week, whereas in the Upper Mississippi River Valley flights have been observed with 30-50 moths/week. While scouting for borer activity also be on the lookout for pupae casings protruding from the trunk near feeding sites, cracked/scaly bark, or at the base of the tree. Pupae are brown and when fully intact are about 0.5 inch in length; if the adult moth has already emerged they may be half that size; see photos at link below.

Dogwood Borer, NC State Extension, https://content.ces.ncsu.edu/dogwood-borer

DWB are trending towards younger trees, but have been found on M7. Best luck is finding them below the trunk guards or on trees with burr knot or damaged bark. Injury is more a product of the planting trends, e.g., what have growers been planting the last 3 – 5 years, rather than specific to a specific cultivar or rootstock. Larvae have been found in tree that are in their 2nd leaf and up to eight or 10 year old.

Applications for DWB are based on scouting and finding larvae or injury rather than trap captures. If treatment is required, see notes below.
– Assail 30 SG is currently the only labeled alternative to Lorsban for a trunk application targeting DWB. Efficacy trials very and Assail is not currently recommended for control.
– Lorsban is not systemic and must be thoroughly applied to the lower four feet of the tree trunk. In need to investigate if spraying a smaller amount of the trunk (e.g., lower 2 feet) is suitable.
– Lorsban can be applied early in the spring and will provide an active residue for one year. An application at this time would minimize contact of this insecticide with the fruit.
– If fruit are present, do not apply using lower nozzles of an airblast sprayer; use a hand wand, shielded sprayer or other method where drift onto fruit can be avoided.
– The application may also be made post harvest, if other blocks are found to be infested during the growing season.
– Some growers have reported using an herbicide sprayer that has been carefully cleaned prior to the trunk application. There are a number of issues that should be carefully considered before using this strategy, see http://extension.missouri.edu/p/G4852 for some of these.

Below is a good video showing one application method:
o Lorsban trunk spray for peachtree borer, Jon Clements, https://www.youtube.com/watch?v=zjSf6sGsg0Y

Additional resources
o Scaffolds Fruit Journal, April 4 2016, http://www.scaffolds.entomology.cornell.edu/2016/SCAFFOLDS-4-4-16.pdf
o Managing Stress: Dogwood Borer in High Density Apple, The Jentsch Lab, May 24 2016, https://blogs.cornell.edu/jentsch/2016/05/24/managing-stress-dogwood-borer-in-high-density-apple/
o What Wood Borers Do? – What’s in the Trunk?, Scaffolds Fruit Journal, April 17 2017, http://www.scaffolds.entomology.cornell.edu/2017/SCAFFOLDS-4-17-17.pdf

Preharvest interval