Gray Leaf Spot

Symptoms — Long, thin, rectangular lesions, up to 2 inches in length, appear on leaves. The lesions start out tan and usually turn gray.

Geography — The disease can be found across the Midwest, Midsouth and some of the Northeast region of the United States. Pockets of Illinois, Indiana, Iowa, Kentucky, Missouri, North Carolina, Pennsylvania, Tennessee, Virginia and West Virginia are at particularly high risk for the disease.

Timing — Late June through September. Disease will start to spread rapidly in late August and early September if conditions favorable to the pathogen are present.

Conditions for development — High humidity and warm temperatures of at least 80 F.

Scouting tips — Spores spread by wind and rain. Start looking for the lesions about two to three weeks prior to tasseling when symptoms typically begin to appear on lower leaves.

Effect on yield — The disease appears in cornfields most growing seasons without significant effect on yield. If conditions favoring the disease are especially persistent, then yield losses in excess of 50% can occur if left untreated.

Management tips — Choose resistant corn varieties with your retailer, rotate crops, till fields to encourage decomposition of infected residue, and apply a fungicide preventively or, if necessary, curatively. DuPont™ Aproach® Prima fungicide is very effective at controlling stripe rust with preventive and curative modes of action. Visit AproachPrima.Corteva.us to learn use rates of the fungicide in corn.

 

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