Plant pathologists at Iowa State University and University of Kentucky have confirmed that isolates of Cercospora sojina, the pathogen that causes frogeye leaf spot of soybean, have shown resistance to quinone outside inhibitor (QoI, strobilurin) fungicides in Iowa.
Frogeye leaf spot (Fig. 1) occurs across the United States, and significant yield loss can occur when this disease is widespread within a soybean field. Plant pathologists estimate that this disease was responsible for more than 17.5 million bushels of lost yield, valued at $158.1 million, across the U.S. in 2015.