Fruit Crop Pest Report- July 22, 2019

2019 Fruit Pest Update

July 22, 2019

2019 – 2020 Midwest Fruit Pest Management Guide

This week was characterized by RAIN. And lots of it. Sweet cherry harvest and early tart cherry harvest is ongoing. Grapes are at bunch closure.

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.

Spotted wing drosophila have been caught in all traps in the county and in very high numbers. Frequently updated trap catches can be found here: https://peninsular.ars.wisc.edu/apple-cherry-pest-update/

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

Date 7/22	2015	2016	2017	2018	2019	5 yr avg
Base 50	900	1063	966	1196	891	1002

INSECT & DISEASE CONTROL

APPLE

Disease Pressure – Apple growers can begin 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 continue to be over threshold in pheromone traps in some scouted apple orchards. If you are still seeing high trap catches (greater than 5-7 moths per week) a third cover may be necessary. Yellow sticky cards for monitoring apple maggot should be out at this time. Once a first fly is caught, 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). No apple maggot have been caught so far. European red mite numbers are low to none. No brown marmorated stink bugs have been caught. First white apple leaf hopper and potato leaf hopper have been detected.

CHERRY

Disease Pressure – Due to the rain, continue monitoring for cherry leaf spot, but there are very few active lesions in scouted orchards. If things dry out this week, disease pressure should be slightly lower. Secondary infections 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 exploded. Flies have been caught in all the traps in the county and one trap had over 800 flies in the one-week sample. Growers are advised to use a 4 to 7-day, full cover control, now 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. (For other insecticides with good control for SWD, read 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.

Below is a chart of the SWD first trap catches from the past 7 years. The years that have had the shortest time between days when there was the first catch and subsequent catches, were also the years when larvae were showing up in tanks at harvest. Based on this, SWD pressure has the potential of being higher than ever before. If you are concerned about your fruit quality, randomly select 30 fruit and soak them in a salt solution and check if larvae emerge within 30 min.

Spotted Wing Drosophila Trap Catches
Year	First Catch	Sustained Catch Countywide	Days Between First & Sustained Catch Countywide
2013	7/21	8/11	21
2014	7/11	8/1	21
2015	7/3	7/17	14
2016	6/10	7/15	35
2017	6/16	6/23	7
2018	6/8	7/16	38
2019	7/12	7/17	5

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.

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.