Multiple resources will help you track potato late blight

Five-day potato late blight forecast, Twitter-page and Blightcast up and running for Michigan for 2011.

The disease-forecasting model that generates accurate predictions of late blight risk up to 5 days in the future is up and running for 2011. 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 or going directly to the forecasting webpage.

A 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. The new 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, which 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 Twitter addition to the late blight disease-forecasting site in 2010 proved popular and has been kept for 2011. Growers and other stakeholders have 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 late blight home page or go to

For the 5-day forecast; variables included to generate the risk status are the day of the year; latitude and longitude of the weather stations; maximum and minimum temperatures; 12-hour Probability of Precipitation forecast (PoP), Quantitative Precipitation Forecast (QPF), and cloud cover values extracted directly the National Weather Service. Additional variables derived from these extracted values were daily temperature range, sum of 12-hour PoP values, clear days (both 12-hour cloud cover values indicated clear) and cloudy days (both 12-hour cloud cover values indicated cloudy). Potato late blight day typing values from the Michigan State University modified-Wallin method included a dry day DSV (assuming no precipitation), a wet day DSV (assuming enough precipitation throughout the day to keep the relative humidity above 80 percent), and the range of DSV values between the wet and dry day calculations.

Funding from Project GREEEN, MPIC, the North Central IPM program and Plant Pathology Department at MSU.

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