Signs of Anthracnose Leaf Blight on your seedlings? No Need to Fret!

June 5, 2019 8:10 AM
Blog Post

With some planting progress still stalled, many of you are probably finding ways to pass the time, possibly scrolling through Twitter. Adding to some of the anxiety, you’re probably seeing photos of diseased seedling corn, by the name of Anthracnose leaf blight. While last week’s article warned you all about this season providing a great environment for disease growth, we’re here to offer you at least some consolation. Though the name may be frightening, at this stage of development, anthracnose leaf blight should not result in long term damage to the crop.

Anthracnose leaf blight is usually present in wet springs, like this one, but does not need to be managed. Research at Iowa State University and University of Wisconsin has shown that there is no relationship between anthracnose leaf blight and anthracnose stalk rot, although both are caused by the same pathogen. Corn will rapidly grow out of the disease, and the affected lower leaves, which do not contribute to yield, will die and fall off the plant within a couple of weeks.

Anthracnose leaf blight is very prevalent in fields that are in a corn-on-corn rotation. The fungus overwinters as mycelium or sclerotia in corn residue. Spores are spread primarily by splashing water. Disease development is favored by wet weather during early crop growth with moderately warm temperatures. Disease develops soon after planting and continues to develop until canopy closure.

An image depicting the anthracose leaf blight disease cycle, from sclerotia to leaf lesions.
An image depicting the anthracnose leaf blight disease cycle, from sclerotia to leaf lesions.

Scouting
Leaf lesions are oval or spindle shaped, tan or brown with dark brown or purple margins, up to 1 inch long and ½ inch wide. As the disease develops, the fungus produces black, spiny fruiting structures on the dead leaf tissue. On severely infected leaves, the lesions can grow together into large dead areas. These leaves may turn yellow and wither. For more information, visit the Crop Protection Network encyclopedia guide. 

 

This article was edited to reflect that the pathogen does not overwinter in seed.

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Alison Robertson Professor of Plant Pathology and Microbiology

Dr. Alison Robertson is an associate professor of plant pathology and microbiology. She provides extension education on the diagnosis and management of corn and soybean diseases. Her research interests include Pythium seedling disease of corn and soybean and Goss's wilt. Dr. Robertson receiv...