Corn Plant Diseases: Anthracnose

A disease that gets a lot of attention in late season health is anthracnose. This disease is prevalent all year round and chips away at the yield of the plant. The ideal condition for this fungus is warm humid weather with more prevalent fungus explosions after a period of rainy cloudy days. This disease affects the late season plant health with anthracnose rotting the stalk of the corn plant which ultimately affects the stalk strength. Anthracnose can affect the yield from very little to up to a 40% reduction depending on the time it attacks the plant and the environmental conditions. This disease is a fungus that lives in corn residue on the surface and on the residue in the top soil. Knowing that anthracnose lives in the soil, there are two ways it can affect the plant.

One way is by infecting the roots of the corn plant in the soil, and as the fungus grows it spreads into the stalk of the plant which later in the season causes the bottom leaves to die and the bottom of the stalk to soften. This causes the less resistant plants to lodge, leaving ears in the field, thus reducing the yield.

The second way anthracnose infects corn plants is from the rain splashing up on to the leaves and infecting the leaves. This introduction of plant infection produces the blight infections and the lesions on the leaves. This type of fungus infection works its way up and down the plant through the splashing and through the vascular system of the plant. If the blight shows up early and continues to progress that is when the yield loss is greatest since it affects the whole plant and causes an early death of the corn plant. Early death of the corn plant will reduce the yield and lower the test weight of the corn.

A preventive measure to help defend against this disease is to spray fungicide if the blight shows up before six weeks after tasseling. If the disease spreads six weeks after tasseling then studies have shown there will be little effect on the yield of the corn plant. Making sure your field fertility is managed properly is a very important control method since this disease can spread faster in under fertilized fields. Also, using proper rotation and tillage practices will help suppress the spread of the disease since the fungus lives in the field corn residue. Any farming practice that helps breakdown or bury the material will help suppress the disease even further. If you know there is a field that is heavily inoculated with the disease choosing the correct corn hybrid that has good stalk strength and good late season plant health will help combat the effects of the anthracnose disease.

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Josh Lamecker

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