Damon L. Smith, Extension Field Crops Pathologist, University of Wisconsin-Madison, Jaime Willbur, Graduate Research Assistant, University of Wisconsin-Madison
Using Sclero-cast: A Soybean White Mold Prediction Model
**This tool is for guidance only and should be used with other sources of information and professional advice when determining risk of white mold development. We encourage you to read the model how-to guide which can be downloaded by clicking here**
Continued dry conditions over the past couple of weeks have helped to continue to decrease white mold risk in non-irrigated fields. Some areas of high risk still exist in the southern and eastern portions of the state. However, many fields we have visited are moving to R3 and R4 growth stages. Thus, they are getting outside of the extremely critical period for infection by the white mold fungus. Some reports of symptoms of white mold are beginning to come in. I suspect we will begin to see more symptoms of disease over the next couple of weeks and will begin to get an understanding of how severe the epidemic will be this year.
Risk remains high for any soybeans planted to 15-inch rows AND irrigated. This planting and management scenario is highly conducive for white mold development. We continue to find apothecia under irrigation and in 15-inch row-spacing. I would expect to see significantly higher levels of white mold in irrigated soybeans planted to 15-inch rows. Risk of white mold remained steady for soybeans planted to 30-inch rows and irrigated. Risk remains high in the southwestern and western portions of Wisconsin for soybeans planted to 30-inch rows and irrigated.
Forecasts indicate cool temperatures with chances of precipitation for the next week. I would expect white mold risk to hold steady. Continue to growth-stage soybeans and note that map predictions should be considered for making white mold management decisions if soybeans are flowering AND soybean canopies are nearly closed. We have visited fields all over the state and find soybeans well into the reproductive growth stages. We are quickly getting outside the window of opportunity to treat for white mold. Any remaining white mold management decisions should be made very soon.