Management of Foliar Fungal Diseases in Soybean in Brazil

Eleven foliar fungal diseases have been found on soybeans [Glycine max (L.) Herrill] in Brazil. Of these, frogeye leaf spot (Cercospora sojina), brown spot (Septoria glycines) and Cercospora leaf blight (Cercospora kikuchii) are of major concern. Downy mildew (Peronospora manshurica), target spot (Corynespora cassiicola) and soybean rust (Phakopsora paohyrhizi) have occasional outbreaks. Of all the foliar diseases, frogeye leaf spot has caused the greatest impact on yield (up to 100% loss) but it is currently under control by use of resistant varieties. Brown spot and Cercospora leaf blight are the most important late season diseases. They may cause more than 20% yield loss (ca. US$ 1 billion worth) annually, in disease favorable years. The possibilities of reducing los ses due to late season diseases through varietal resistance or tolerance and fungicide sprays are demonstrated but these practices are not used routinely. Chemical seed treatment and integrated crop management for reducing the inoculum potential in the field are emphasized.