By Andi Anderson
Michigan State University (MSU) has launched two updated weather-based decision support tools to help potato growers better manage disease risks and improve crop protection. Available through the MSU Enviroweather platform, the new tools provide region-specific information that can assist growers in monitoring conditions favorable for disease development and volunteer potato survival.
One tool focuses on Potato Late Blight Risk, a serious disease that affects potatoes and tomatoes. Late blight, caused by Phytophthora infestans, can spread rapidly under favorable weather conditions and severely damage crops. Symptoms include dark, water-soaked spots on leaves and stems, often accompanied by white mold-like growth on the underside of leaves during humid conditions.
The late blight tool uses temperature and humidity data collected from weather stations to calculate Disease Severity Values (DSVs). Unlike older models that relied on fixed dates, the updated system allows growers to customize important information such as crop emergence dates, fungicide application dates, and forecast periods. This flexibility helps farmers evaluate disease pressure throughout the growing season and make timely management decisions.
The risk map categorizes conditions into five levels: Very Low, Low, Medium, High, and Very High. Growers can also review disease risk forecasts for the coming week, helping them prepare for potential infection periods before they occur.
The tool provides detailed information for individual weather stations, allowing users to closely monitor local conditions. As of mid-July 2026, no cases of late blight had been reported in the United States or Canada. However, experts continue to encourage monitoring because favorable weather can quickly increase disease risk.
A second tool, the Potato Volunteer Survival Risk Map, helps growers assess the likelihood that volunteer potato plants survived winter conditions. Volunteer potatoes can create significant challenges because they may harbor diseases, viruses, and pests that can affect future crops.
The survival map uses soil temperature data collected during winter. The model measures the number of hours soil temperatures remain below 27°F at different depths and classifies risk as Low, Moderate, or High. Fields that experience prolonged cold soil temperatures generally have lower risks of volunteer potato survival.
A unique feature of this tool is its historical database, which allows users to review volunteer survival risk dating back to 2008. This information can help farmers compare different years and better understand long-term patterns.
Based on winter conditions during 2025-2026, the model predicted a high volunteer potato survival risk across Michigan. Although air temperatures were cold, soil temperatures did not remain low enough for a sufficient period to eliminate most volunteer tubers.
These new MSU Enviroweather tools provide growers with valuable information for disease prevention, scouting, and management planning. By combining weather data with research-based models, farmers can make more informed decisions, improve crop protection strategies, and reduce potential losses throughout the growing season.
Photo Credit: gettyimages-npantos
Categories: Michigan, Crops, Fruits and Vegetables