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Issue No. 10, Article 5/June 11, 2010

Anthracnose Leaf Blight of Corn

Symptoms of anthracnose leaf blight of corn are being observed throughout the state. This disease is caused by the fungus Colletotrichum graminicola. Because the fungus overwinters in corn debris, symptoms are more likely to appear in fields that were corn the previous year and those that have a lot of corn stubble still present on the soil surface. Symptoms of anthracnose can be observed as brown lesions on the leaves. Some lesions may contain dark fruiting structures known as acervuli. In most observations so far this season, lesions appear to be present on the lowermost leaves only.

Symptoms of anthracnose leaf blight on a corn leaf.

Most available information suggests that once corn reaches or exceeds the 6-leaf stage, leaf lesions do not generally spread to the upper leaves, as the plant begins to produce phenolic compounds that can inhibit the fungus. Colletotricum graminicola also causes a stalk rot of corn, but leaf lesions are not an indication that stalk rot will occur later on. Root infection by the fungus is more likely to result to stalk rot than foliar infections. For these reasons, it is unlikely that applying a foliar fungicide to corn at early growth stages to control anthracnose leaf blight will result in a yield benefit. For more information about foliar fungicide applications to corn at early growth stages, refer to the April 23 issue (no. 3) of the Bulletin.--Carl A. Bradley

Carl A. Bradley

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