Michigan potato late blight forecast – June 20, 2018

Potato late blight risk is moderate in the Upper and Lower Peninsula, including western, central, and some eastern growing regions.

Late blight forecast
Figure 1. June 20, 2018 – Michigan late blight forecast based on accumulation of disease severity values (DSVs) since early May emergence. Yellow pins on the map indicate medium risk areas and currently include all western and central regions. Green pins indicate low risk.

The Michigan Late Blight Forecast Tool is currently calculating 2018 risk predictions. No potato late blight has been reported yet this season in Michigan. Due to the warm, wet weather we have been experiencing, however, late blight risk has risen to moderate levels in many areas (Fig. 1).

Late blight is caused by Phytophthora infestans, which favors 60-80°F 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

Medium risk

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.

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