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Physoderma Brown Spot

August 4, 2000

Matt Montgomery reported Physoderma brown spot on leaf sheaths of corn. Symptoms of this disease are common and appear as reddish purple to brown, oval to round spots that grow together and form blocky, angular-shaped lesions on the lower leaf sheaths, leaf blades, and the cornstalk. The lesions can also occur on the husks and tassels. The causal organism of brown spot is the fungus Physoderma maydis. This organism overwinters in the soil and in infected tissue, and germinates in the presence of water and light. Typically, infection occurs in the whorl, where moisture can persist for long periods. Infection takes place more readily in young actively growing tissue because plants become more resistant to infection with age. The presence of this disease should not cause concern. It is not usually an economically important disease.--Loretta Ortiz-Ribbing

Author: Loretta Ortiz-Ribbing

The Pest Management and Crop Development Bulletin
Executive Editor: Kevin Steffey, Extension Entomologist

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