Fruit Crop Pest Report – May 6, 2019

2019 – 2020 Midwest Fruit Pest Management Guide

Apples are at green tip to ¼” green in most blocks, so apple scab sprays should begin on a 7-10 day schedule (see disease section below). Rain in the forecast will likely bring the first apple scab infection periods.

Cherries are primarily at open cluster so there are no sprays necessary at this time. Grapes are at bud swell and there are also no concerns at this time.

Currently, critical temperatures for 90% flower bud kill have risen to between 15ºF & 20ºF for cherry and apple at their current stage of development. Grape buds continue to be slightly more tolerant of cold temperatures at this time, but will be less so when buds begin to swell. Click a link below for more information on tree fruit crop bud cold temperature injury.

Tree Fruit – Critical Temperatures

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

Date 5/6	2015	2016	2017	2018	2019	5 yr avg
Base 50	84	65	52	66	30	59

Delayed dormant applications for control of early season disease and insect pests can still be made, but limited time remains to make these type of applications.

Continuing scouting for overwintering mite eggs. If red eggs are present, overwintering mite eggs can be controlled now through tight cluster on apple with a 1-2% oil application (1-2 gal dormant oil per 100 gal water). Be aware that the later you make this type of application that you might consider the lower 1% application rate as phytotoxicity can be a risk, especially if you combine a copper fungicide for the control of early scab. Do not apply oil 48 hours before or after a frost. Captan should be avoided when making early season oil applications.

INSECT & DISEASE CONTROL

APPLE

Disease Pressure – Apple scab spray programs should begin to protect apple scab susceptible varieties (e.g. McIntosh and Cortland), as the 1/2 inch green through first cover time period is the most critical time for primary scab infections to occur. Keep these varieties covered with fungicide treatments through the end of primary scab season; typically mid to end of June in Northeast WI. Applications of copper can still be made to reduce fire blight inoculum. These copper sprays will also provided protection from apple scab infection.

Insect Pressure – Green fruit worm flight is mostly complete, but they do not yet pose a damage threat. Scout for presence of their larva as well as overwintering oblique banded leafroller larva starting at the ½ inch green stage of development through petal fall.

CHERRY

Disease Pressure – Little to worry about because of plant stage

Insect Pressure – Green fruit worm flight is mostly complete, but they do not yet pose a damage threat. Scout for presence of their larva as well as overwintering oblique banded leafroller larva starting at the open cluster stage of development through petal fall.

GRAPE

Disease Pressure – Little to worry about because of plant stage

Insect Pressure – Little to worry about because of plant stage. As buds begin to swell, keep an eye out for grape flea beetle damage (see WI Fruit News article at the link below).