By Pierce Paul, Ohio State University Extension
This July has been one of the wettest on record, and with the extra moisture, comes concerns about diseases. Gray Leaf Spot (GLS) and, to a lesser extent, northern corn leaf blight (NCLB), have already been reported in some fields, well before tasseling in some cases. Such early disease development could impact grain yield, especially if it continues to be wet and the hybrid is susceptible. GLS is favored by warm temperatures (70 and 90 F) and high relative humidity. NCLB is also favored by wet, but slightly cooler (64 and 80 F) conditions, than GLS. Over the last several days, we have had temperatures within the favorable range for both diseases, and if they continue to spread and damage the ear leaf before grain fill is complete, yield losses could be high.