Foliar Health Basics: Gray Leaf Spot Control
Gray leaf spot, caused by the fungus Cercospora zeae-maydis, is a primary foliar corn disease in the United States. It overwinters on corn residue and spreads from soil to young plants by splashing rain or from field to field by wind.
The gray leaf spot pathogen builds up in corn residue over time, making the disease more common in minimum-tillage fields. Warm, humid conditions promote fungal growth, and leaf infection occurs during long periods of damp or foggy conditions when plant leaves remain wet for at least 12 hours. Scout corn at V14 or prior to tassel emergence to determine the level of disease pressure.
Signs of Infection
Small, pinpoint lesions surrounded by yellow halos first appear between veins of corn leaves and can be difficult to distinguish from other foliar diseases, but as lesions mature they lengthen to up to 2 inches and turn brownish gray. Lesions can rapidly spread, destroying much of the corn’s photosynthetic ability and threatening yields.
If the disease causes significant leaf loss before grain fill is complete, yield loss can range from 15 to 50 percent. When this happens, carbohydrates are taken from stalks to fill kernels, causing stalk rot and lodging.
Hybrids with genetic resistance can reduce yield loss from gray leaf spot, but no hybrid is immune. Gray leaf spot has a longer survival time in crop debris than other residue-borne pathogens, although crop rotation can help reduce disease pressure. An application of 6.8 fluid ounces per acre of DuPont™ Aproach® Prima fungicide made at VT to R2 helps protect the upper leaf canopy to maximize green leaf tissue, which supports yield potential.
DuPont™ Aproach® Prima fungicide is not registered in all states. See your DuPont retailer or representative for availability in your state.
Headline® (BASF); Stratego® (Bayer); Quilt Xcel® (Syngenta).
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