Michigan potato late blight forecast – July 17, 2019

No late blight reported. Weather-based risk remains moderate throughout Michigan growing regions.

Michigan late blight forecast
Figure 1. July 17, 2019 – Michigan late blight forecast based on accumulation of disease severity values (DSVs) since early May emergence. Yellow pins indicate medium risk areas and green pins indicate low risk.

The Michigan late blight forecast tool is currently calculating 2019 risk predictions. No potato late blight has been reported yet this season in Michigan. Despite the sustained wet weather we have been experiencing, the higher temperatures have led to continued moderate late blight risk in most areas (Fig. 1).

Late blight is caused by Phytophthora infestans, which favors 60-80 degree Fahrenheit 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 Enviroweather. A customizable tool for early or late emergence scenarios is also now available.

Please visit the MSU Potato and Sugar Beet Pathology website for more information. Answers to frequently asked questions about this forecast tool are also available.

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