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Disease Risk in Hail Damaged Corn (07/20/17)

Several corn fields in the last two weeks have experienced significant hail damage. With this added injury, questions have been asked on disease risk in corn.

Disease Risk in Hail Damaged Corn

Several corn fields in the last two weeks have experienced significant hail damage. With this added injury, questions have been asked on disease risk in corn. Over the past three years, the NDSU Extension Cereal Crop pathology program has conducted a corn survey (partial funding from North Dakota Corn Utilization Council) to assess disease prevalence in the state. The four most common diseases observed from these surveys include common corn rust, Goss’ leaf blight and wilt (Goss’ wilt), northern corn leaf blight, and common smut. Of these four diseases, two will have a higher incidence after hail; Goss’ wilt and common smut. Stalk rot risk may also increase as opportunistic pathogens (i.e.: Fusarium) colonize stem tissue, but symptoms often are not observed until corn nears maturity.

Goss’ wilt is caused by a bacterium and overwinters primarily on corn residue. Bacteria need a wounding event (hail, sand blasting, wind whipping, etc.) to enter a host plant. After entering, warm and humid weather will favor disease development. Symptoms include water-soaked (greasy) lesions extending along the midrib of a corn leaf (Figure 1). Advanced infections will have characteristic “freckles” embedded within a lesion. Lesions often are first noticed on the leaf tip and extend towards the stalk. The greatest amount of yield loss is observed with early infections on susceptible hybrids. The best management strategy involves the use of resistant hybrids, crop rotation and residue management. Fungicides do not manage this disease.

Common smut is a  frequently seen disease that rarely has economic implications in ND. This disease is associated with gray to white galls filled with black spores (Figure 2). Galls are most often seen on cobs and kernels, however galls can also form on stems and leaves. Management of common smut is not needed due to its low economic impact.

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Andrew Friskop

Extension Plant Pathology, Cereal Crops

 

Elizabeth Bauske

NDSU Plant Pathology, Research Specialist

 

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