I have had a few emails, tweets and phone calls from folks who are starting to find disease in corn in Iowa.
It is very common to find anthracnose leaf blight on the lower leaves of young corn plants, particularly in corn-on-corn fields. If you know the disease cycle of this pathogen, this should be no surprise given all the spring rain we have had. Colletotrichum graminicola survives in surface corn residue. In moist conditions in the spring, it produces spores on the residue that are splash-dispersed onto these lower leaves. Infection and colonization of the leaf tissue occurs, and we see the dark irregular-shaped lesions on the bottom four to five leaves. Once canopy closure occurs, it is rare to see anthracnose leaf blight and, because it occurs so early in the growth of the plant, it does not affect yield. Furthermore, data from both Iowa and Wisconsin found no relationship between the incidence of anthracnose leaf blight and anthracnose stalk rot.
Iowa State University
Robertson, Alison E., "Anthracnose Leaf Blight, Common Rust, Gray Leaf Spot and Goss’s Wilt Found in Iowa" (2013). Integrated Crop Management News. 43.
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