A Summer 2009 Update on Diseases in Iowa Soybean

Xiao-Bing Yang, Iowa State University
Shrishail Sharanappa Navi, Iowa State University

This article is from Integrated Crop Management News.

Abstract

The association of plant disease with extreme weather is well documented, so it is no surprise that this year’s extreme weather with record cool temperatures and plenty of rain has created favorable conditions for disease development in soybean. Disease that we are seeing includes sudden death syndrome (SDS) and several soybean foliar diseases, the most prevalent are Cercospora leaf blight, soybean brown spot, bacterial blight, and downy mildew. As August temperatures begin to heat up diseases such as Cercospora and frogeye leaf spot can increase. This will create a mixed bag of cool and warm diseases that can cause premature defoliation. Because of the potential disease mix, assessing the risk to crops is difficult.