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Clemson University - USDA Cooperative Extension Slide Series

Physoderma brown spot; Stalk rot

Physoderma maydis

Physoderma brown spot; Stalk rot (Physoderma maydis) is a fungal pathogen. It was first detected in Nebraska in 1984.

Physoderma brown spot is caused by the fungus Physoderma maydis, which is closely related to the oomycete or water mold fungi, such as the downy mildews. This disease is normally an infrequent, minor disease in corn, However, during some summers when weather conditions are more conducive for disease development, the disease can develop and greater incidence and cause alarm because its symptoms are similar to some other more serious diseases.

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