By Loren Giesler, Extension plant pathologist, University of Nebraska

Recently Iowa State University confirmed Cercospora sojina, the pathogen that causes frogeye leaf spot of soybean, having resistance to quinone outside inhibitor (QoI, strobilurin) fungicides in Iowa.

This report is a reminder to all of us of how important resistance management is for pathogens as well as weed and insect pests. While we have not identified C. sojina to have fungicide resistance in Nebraska, due diligence is needed by all farmers to ensure practices are not encouraging resistance development. A map of the current distribution of strobilurin-resistant frogeye shows  there is good distance between Nebraska and any confirmed fields at this time.

A plan for resistance management includes:

Additional resources on Resistance Management are available on the CropWatch Resistance Management page and the Crop Protection Network. See Fungicide Resistance in Field Crops FAQs (CPN-4001).