Forecasts identifying favorable environmental conditions for potato late blight are available daily

New five-day forecasting model will increase information for Michigan growers to make potato late blight management decisions.

Environmental conditions favorable for potato late blight (measured as disease severity values or DSVs) have accumulated to above threshold in much of southern and the far western portion of the lower peninsula of Michigan and farmers in those areas are advised to start protective fungicide applications. However, DSV accumulations as of June 15 were not yet at threshold in Montcalm County, the Thumb or the northern or Upper Peninsula growing areas. On the website, DSV and risk can be calculated for individual fields using the date of emergence as the starting point for the accumulation

The disease-forecasting models were developed with funding from Project GREEEN, the North Central IPM program, MPIC and the potato pathology program at MSU. Dr. Kathleen Baker at Western Michigan University developed a disease-forecasting model that generates accurate predictions of late blight risk up to five days in the future. The potato late blight prediction model has been available to growers through the Late Blight Risk Management website run by MSU since 2000. This model is used to estimate environmental conditions that are favorable for epidemic risk and then provides fungicide recommendations appropriate to that risk. Growers can select appropriate fungicides from the table or use MSU Extension Bulletin E-312, Nematode, Insect and Disease Control.

The new five-day forecasting model derives hourly microclimate variables associated with potato late blight risk from National Weather Service forecast data. This data is then fed into a neural network computer program that generates high or low risk estimation. Although this new model is not a replacement for the old model, it increases the amount of information available to growers, enabling them to take the necessary preventative actions to manage late blight risk, such as the timely application of an effective fungicide. The new model is now available on the late blight website by clicking on the “5-Day Forecast” link in the left hand menu on the home page.

Another new addition to the late blight disease-forecasting site is the ability to keep track of important news on late blight in Michigan using Twitter. To follow the late blight site on Twitter, click on the “Follow us on Twitter” button on the home page. Updates on late blight across the state and nationally are sent to your phone as a text message as we learn of them.

Weekly updates are recorded to the Syngenta potato late blight hotline for Michigan at 888-379-9012.

Dr. Kirk's work is funded in part by MSU's AgBioResearch.

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