Fruit Crop Pest Report- August 26, 2019

2019 Fruit Pest Update

August 26, 2019

2019 – 2020 Midwest Fruit Pest Management Guide

Conditions have been dry and we got some much-needed rain today. We are still behind normal for degree days, and apple harvest will also likely be delayed. We will start publishing apple maturity reports next week. Grapes are at veraison.

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

Date 8/26	2015	2016	2017	2018	2019	5 yr avg
Base 50	1523	1780	1508	1880	1465	1617

INSECT & DISEASE CONTROL

APPLE

Disease Pressure – Disease pressure continues to be low with the dry weather. Apple scab lesions on fruit or leaves, powdery mildew, and fireblight strikes are nearly impossible to find. Drier conditions the last couple weeks resulted in little pressure from late season diseases including sooty blotch and fly speck, except in poorly ventilated orchards with excessive foliage from poor pruning and/or over fertilizing. Unless we have a rainy fall, we expect this pattern to continue.

Insect Pressure – Second generation codling moths are slightly below threshold this week in most blocks. Based on degree days since biofix, the first spray for the second generation codling moth should have gone out last week and if above threshold, a second spray should follow 10-14 days later. There is a large spotted tentiform leafminer flight and moderate leaf roller larval activity. Apple maggot flies are being caught in low to moderate numbers. When spraying for coding moth, it is recommended to make sure that the product you use will work against these pests as well. There have not been any European red mites populations above threshold found in scouted orchards.

Summer pruning can continue through this week to improve apple coloring. Be aware that suddenly exposing shaded fruit to sun can lead to photo-oxidative sunburn. ReTain or other plant growth regulators can be applied at this time to aid in fruit coloring and reduce fruit drop before harvest. This is also a good time for late-season weed control. When using any product, make sure to carefully read the label for the preharvest intervals, to avoid issues at harvest.

This article from MSU gives detailed apple maturity information, which is definitely worth reading: https://www.canr.msu.edu/news/west-central-michigan-apple-maturity-report-aug-21-2019. For comparison, at the time of writing, they were at 1560 GDDs in the Ludington area and 1643 GDDs in Hart. All around the region apples appear to be coloring faster than their maturity indicates, so do not rely on color alone to time harvest. We will have local apple maturity data starting in September.

CHERRY

Disease Pressure – If you haven’t already done so, a final cherry leaf spot post-harvest spray can go out now if cherry leaf spot lesions are present. With cooler temperatures continuing this week, copper products or captan should be safe to use. The goal is to keep leaves on until at least the first week of September or later so the trees are as healthy as possible going into the winter. Conditions were ideal in the last two weeks for American brown rot to explode. Shaking fruit to the ground is strongly recommended in unharvested blocks to decrease the chance that mummified American brown rot-infected cherries will infect next year’s fruit.

Insect Pressure –Even though spotted wing drosophila continue to be caught in traps, insecticide applications should stop. Continuing to spray insecticides after harvest could actually speed up the development of insecticide resistance. Check orchards for European red mites because some scouted orchards are currently over-threshold (often due to the frequent use of pyrethroids killing natural enemies of mites). If over threshold, a miticide is recommended to prevent a decrease the leaves’ photosynthetic ability.

This week or next week are the best time to hedge in cherry orchards. You can also mark limbs that you plan to remove during dormant pruning to open up canopies and increase airflow to make the environment less favorable for spotted wing drosophila next year.

GRAPE

Disease Pressure – Untreated vines in the PARS vineyard are showing heavy black rot, powdery mildew, downy mildew, and phomopsis pressure. When using fungicides, be aware of any preharvest intervals.

Insect Pressure – Phylloxera galls are covering leaves on more susceptible varieties, especially Frontenac. Phylloxera needs to be controlled in the early summer, so there is nothing that needs to be done at this time. Leafhoppers are also showing up in the PARS vineyard. Scout your vineyard for small yellow/white stippling on the surface of leaves. If applying an insecticide, consider using a product that controls leafhoppers as well. For more information, click here.

Leaf pulling to allow for more light penetration to the fruit should be ongoing. As fruit begins to color, bird control measures need to be considered, such as squawkers, avian sprays, lasers, or netting.