Fruit Crop Pest Report- June 17, 2019

2019 Fruit Pest Update

June 17, 2019

2019 – 2020 Midwest Fruit Pest Management Guide

Apples are just past petal fall and cherries are at just out of the shuck in most Door county orchards. Grapes are around 6-12” shoots.

Below is a degree day comparison of the last five years. We are still about a week behind average and temperature forecasters are predicting that this cool weather will continue. According to the Sturgeon Bay weather station, we have only had two days over 80F so far this year (5/25 and 5/31).

Date 6/17	2015	2016	2017	2018	2019	5 yr avg
Base 50	388	421	424	528	264	428

INSECT & DISEASE CONTROL

APPLE

Disease Pressure – Based on the Enviroweather spore forecaster, apple scab ascospores are fully mature and about 80% discharged. Apple scab infection periods continue to occur at all the stations, but the end of primary apple scab season is in sight. So far there haven’t been any apple scab lesions detected in sprayed orchards. Cool temperatures have kept fire blight pressure low. Based on current weather predictions, risk of infection could greatly increase later this week if there is rain and temperatures are in the upper 70s.

Insect Pressure – We have still not caught any plum curculio or spotted wing drosophila. I am very surprised that we have not seen plum curculio yet this year and I’m not sure why (the winter? Current temperatures?). Fruit is susceptible to damage, so make sure to scout your orchard for crescent-shaped egg-laying scars on fruit so you don’t overlook their presence in your orchard. One codling moth was caught in only one trap in the county this past week. Biofix occurs when moths are caught in two successive trap catches. The first cover spray should go out at 250 DD past biofix, followed by a second spray 10-14 days later. Cooler temperatures may influence when biofix occurs, since the moths are primarily active if it is over 60F in the evening, which we haven’t had the last few days . A few obliquebanded leafrollers and spotted tentiform leafminers were caught this past week as well.

CHERRY

Disease Pressure – – Cherry leaf spot has been detected in multiple commercial blocks and is setting itself up to be a major issue this year. It is going to be very important to apply full covers with short windows of time between sprays, especially if rain events continue. Do not use only protectant fungicides, because they will not control the leaves that are already infected. Note: Do not use Bravo fungicides if fruit is past shuck split.

Insect Pressure – There has been some light feeding from various leaf-feeding insects observed, but nothing significant. So far there haven’t been any plum curculio adults or spotted wing drosophila flies caught in traps. Fruit is susceptible to plum curculio damage, so make sure to scout your orchard for crescent-shaped egg-laying scars on fruit so you don’t overlook their presence in your orchard, even though we have not found any yet. Even though it is has been wet, scout for European red mites, especially in blocks where there has been a lot of use of pyrethroids for SWD control in the past few years. Lone SWD flies continue to be caught in Michigan, but fruit are not susceptible to damage at this point. Continue to scout for green fruitworm and obliquebanded leafroller damage through petal fall.

Michigan State University recently published an article, “Low spray programs for tart cherry.” Just make sure to check that any product you use is registered for Wisconsin.

GRAPE

Mark your calendar for July 18, 3-5pm, for the 2019 Vineyard Walk at the Peninsular Ag Research Station!

This is the optimal timing for thinning shoots, before they get too woody with tendrils. Thin shoots to about 6-8 per foot, depending on the vigor of the vine (leave more shoots for more vigorous vines). Disease Pressure – Fungicide applications can begin around 4” – 6”growth. Black rot leaf lesions were found in the PARS vineyard

Insect Pressure – Scout for flea beetle larvae at this time. Larval damage rarely reaches economic levels. A few grape plume moth larvae were found as well, but they also very rarely would cause enough damage to warrant an insecticide application. Reddish-purple blobs/spots from grape tumid gallmaker is showing up on stems and leaves. If found, prune out any damaged sections and destroy the leaves.