Diseases on corn for silage

Plant diseases can impact corn grown for silage by lowering yield and causing molds and mycotoxins.

Increasing attention is being paid to the impact of plant diseases, including foliar diseases, on field corn in Michigan. These problems are not limited to corn grown for dry, shelled grain. Silage corn can also be affected by plant disease, mostly caused by fungi. All fungal diseases that attack the corn plant have the potential to reduce yield. Loss of dry matter because of tissue death, early plant death resulting in poor ear fill and small kernels, and stalk lodging can be caused by fungal disease and result in lowered yields and general quality. In addition, certain fungal disease organisms contaminate grain and stalks with mycotoxins, such as vomitoxin, causing serious quality problems.

Leaf diseases on silage corn result in formation of lesions on leaves and can result in tissue death, including early death of entire plants, and increased susceptibility to stalk rots. Leaf diseases include northern corn leaf blight caused by Exserohilum turcicum, eyespot caused by Aureobasidium zeae, common rust caused by Puccinia sorghi Schwein, and gray leaf spot caused by Cercospora zeae-maydis (more prevalent in southern Michigan).

Stalk rots on silage corn result in stalk lodging. This can contribute to harvest difficulties and reduced grain and dry matter yields. Diseases causing stalk rots include gibberella stalk rot caused by Fusarium graminearum, Fusarium stalk rot caused by three main species including Fusarium verticilliodes, F. proliferatum and F. subglutinans, diplodia stalk rot caused by Diplodia maydis, anthracnose stalk rot and top-die back caused by Colletotrichum graminicola, and Pythium stalk rot caused by Pythium aphanidermatum and other Pythium species.

Ear diseases result in reduced grain content and quality of silage, and can contaminate silage with highly toxic mycotoxins. Mycotoxins are not broken down during the ensiling process. If your corn is contaminated before harvest, the resulting silage will also be contaminated. Ear diseases include gibberella ear rot caused by Fusarium graminearum (the same pathogen that causes gibberella stalk rot), Fusarium ear and kernel rot caused by Fusarium verticilliodes, F. proliferatum and F. subglutinans (the same three main pathogens that cause Fusarium stalk rot), diplodia ear rot caused by Diplodia maydis (the same pathogen that causes diplodia stalk rot), and common smut caused by Ustilago zeae.

Fungicide use is becoming more common on field corn with emphasis on corn grown for grain. If fungicides registered for corn silage, such as Headline AMP, Quilt Xcel, or Stratego are considered, growers need to pay close attention to the label for pre-harvest interval information.

A 2009-2010 field trial conducted jointly by University of Wisconsin and University of Minnesota personnel resulted in inconsistent responses of corn hybrids grown for silage to fungicide application. These results indicate no economic advantage to using a foliar fungicide and that hybrid selection is still more important than the use of a foliar fungicide. However, rotation, tillage, row spacing, fertility, insect, and weed and herbicide interactions can also be important factors. Scouting for disease in corn silage should ramp up just before tasseling. Familiarity with the appearance of the main diseases is essential.

The articles referenced below have more detailed descriptions with good photos.

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