Reports of gray leaf spot have been numerous this week, after apparently little activity in the previous weeks. The disease has been observed throughout southern Iowa and as far north as Grundy County. Although it is not yet severe in most fields, the warm, humid weather and frequent rain are ideal for the disease this year, and I expect that it will be worse than in the past two years.
Iowa State University
Munkvold, Gary P., "Gray leaf spot is on the move" (1998). Integrated Crop Management News. 2284.
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