Gray leaf spot (GLS) has reached threshold levels in some corn fields in southwestern Iowa and a fungicide application should be considered for these fields. As many as 5-20 gray leaf spot lesions are present on the ear leaf and, in some fields GLS lesions are also present on the leaf above the ear leaf. Approximately one in two plants are infected, and corn is at growth stage VT/R1. A couple of weeks ago, I summarized data from Greg Shaner at Purdue University, that showed fungicide applications can be profitable when disease pressure is high and the infected hybrid is susceptible to gray leaf spot.
Iowa State University
Robertson, Alison E., "Eyespot and Gray Leaf Spot Severity Continue to Increase in Iowa" (2009). Integrated Crop Management News. 597.
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