Scout for foliar diseases in corn such as Northern Leaf Blight and Gray Leaf Spot just before tassel emergence and answer the following questions when considering an application of foliar fungicide:
Many foliar pathogens survive in corn residue, so the risk of foliar diseases (such as gray leaf spot and northern leaf blight) increases when corn is planted into a field that was corn the previous year.
Rainy and/or humid weather is most favorable to foliar diseases. In growing seasons when these conditions prevail, the risk for disease development increases.
Yield losses from Cercospora are typically considered to be minimal in the U.S. and Canada. The leaf phase is not expected to reduce yield unless significant leaf area is lost before soybeans near maturity. Yield loss from the purple seed stain phase of the disease is negligible unless infection is severe, but quality may be reduced. In many cases, the seed discoloration is only cosmetic, affecting the appearance of the grain but little else.