Michigan Late Blight Forecast

Published online: Jul 19, 2018 Articles
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Source: Michigan State University Extension

The Michigan Late Blight Forecast Tool is currently calculating 2018 risk predictions. No potato late blight has been reported this season in Michigan. Late blightrisk remains at moderate levels in most areas; pockets in the northwest, southeast, Thumb and Upper Peninsula have increased from low to medium risk in the past week.

Late blight is caused by Phytophthora infestans, which favors 60- to 80-degree temperatures, high humidity, and frequent rainfall. This online forecasting tool calculates disease severity values (DSVs) based on the duration of temperature and relative humidity conditions that are favorable for disease development. Accumulated DSVs (based on early May emergence) are used to determine the local late blight risk level, indicated by the color of the map marker pins:

Low risk (Green)

Medium risk (Yellow)

High risk

Late blight detected within 2-5 miles

Late blight detected within 1 mile

This tool was developed by Baker et al. 2002 and weather data used in this model is provided by the Michigan State University Enviroweather. A customizable tool for early to late emergence scenarios is currently in development.

Please visit the MSU Potato Disease website for more information. Answers to frequently asked questions about this forecast tool are available.