Fruit Crop Pest Report- August 5, 2019

2019 Fruit Pest Update

August 5, 2019

2019 – 2020 Midwest Fruit Pest Management Guide

Weather was a bit cooler and sunny the last week and things are starting to dry out from all the rain mid-July. Tart cherry harvest is ongoing. Grapes are at bunch closure and are starting to soften.

For all tree fruit crops, if you plan to take leaf samples for tissue testing, late July to early August is the best time. Take 50-100 leaves from several trees that are representative of that block and put them in a paper bag before sending them to a tissue analysis lab. Grape petiole analysis should take place at veraison.

Below is a degree day comparison of the last five years.

Date 8/5	2015	2016	2017	2018	2019	5 yr avg
Base 50	1185	1363	1196	1461	1149	1258

INSECT & DISEASE CONTROL

APPLE

Disease Pressure – Apple growers can continue to increase intervals between protectant fungicides now as primary apple scab season is over. Length of intervals can be increased to 2-3 weeks if scab lesions are not present on leaves or fruit. Apple growers who have scab lesions present in their orchards should continue to apply protectant fungicides on a regular schedule. Last week’s rains may have washed off spray residue and a repeat application for sooty blotch and flyspeck may be necessary along with Captan for scab (see article from the Wisconsin Fruit News at the end of this report). Fireblight continues to have the potential for infection if there is hail or damaging winds.

Insect Pressure – Trap catches for 1^st generation codling moth flight are decreasing as the flight ends. The first apple maggot flies were caught in traps the week of July 29^th. Traps can be switched to red sphere traps, which are more effective as females look for egg-laying sites on ripening apples. (click here for a newer publication on Apple Maggot). European red mite numbers are low to none. No brown marmorated stink bugs have been caught.

CHERRY

Disease Pressure – Disease pressure is less as we dry out a bit. Secondary infections of cherry leaf spot are going to continue to be a threat especially in blocks that did not have good early control. Some powdery mildew is showing up in more sheltered blocks, with less airflow. American brown rot is showing up in some blocks. If you see this in your orchard, make sure your fungicides include this disease on their label.

Insect Pressure – Spotted wing drosophila catches have dropped during harvest to around 20 per trap, probably due to diligent controls pre-harvest. Growers are advised to continue to use a 4 to 7-day, full cover control, through harvest. The most affordable and effective controls for SWD are Imidan and Mustang Maxx (among other pyrethroids). It is highly recommended that these controls be rotated for resistance management. For example, if Mustang Maxx is applied, the next application, 7 days later, should not be a Mustang Maxx or any other pyrethroid, but Imidan. This pest has short generations time (7-21 days) and by rotating classes regularly we avoid exposing consecutive generations to the same chemistry. (Reach MSU’s most recent SWD management guide, here). MSU has done some research looking at the rainfastness of different insecticides. The results can be found here: https://www.canr.msu.edu/news/rainfast_characteristics_of_insecticides_on_fruit

NOTE: Please be aware of re-entry intervals (REI), especially for pick-your-own harvesting and Pre-Harvest Intervals (PHI). Mustang Maxx is still under a Section 24(c) Special Local Need label through the end of 2020, allowing for a 3 day PHI, FOR TART CHERRY ONLY (more info here).

No cherry fruit fly have been caught. Once cherry fruit fly become active, an insecticide should be applied within one week of a catch on yellow sticky traps. European red mite populations have been low to none.

After harvest, there is no advantage to continuing to make control applications for SWD. Continuing to spray insecticides after harvest could actually speed up the development of insecticide resistance.

GRAPE

Disease Pressure – Secondary black rot, powdery mildew, downy mildew, anthracnose, and Phomopsis are showing up in the PARS vineyard. Continue to scout for diseases and use a fungicide spray every 7-10 days as needed. If bunch rots have been an issue in the past, fungicides need to be used before bunch closure for good coverage.

When scouting for diseases, former UW graduate student, Dave Jones, made an excellent photo disease guide per variety that can be found here: https://fruit.wisc.edu/wp-content/uploads/sites/36/2017/04/Photo-guide-diseases-cold-climate-grape.pdf.

Insect Pressure – Japanese beetle are starting to show up in the central part of the county. Phylloxera leaf galls are present throughout the vineyard. No treatment is needed this year (see article in the Fruit News below).