Frogeye Leaf Spot Resistance Increasing in Soybean

Frogeye Leaf Spot Resistance Increasing in Soybean February 21, 2018

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.

Soybean frogeye leaf spot
Figure 1. Frogeye leaf spot.

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 at Integrated Pest Management – Pest Information Platform for Extension and Education (ipmPIPE) shows  there is good distance between Nebraska and any confirmed fields at this time.

A plan for resistance management includes

  • the use of genetics to reduce disease potential,
  • residue management and rotation to break down inoculum of the pathogen, and
  • the treatment of fields before significant levels of disease are present using fungicides with multiple modes of action.  

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).