Heat stress or high temperature disorder Pathogen: None - not a disease. Signs/Symptoms: Scorched leaf tissue usually associated with lack of water and hot weather. Certain inbreds are very susceptible. Symptoms frequently appear first on the flat part of the leaf as white or yellow stripes between the green veins. The terminal portion of the leaf may die. If the dead tissue is colonized by secondary fungi such as Cladosporium and Alternaria, it will have a gray or black appearance that might initially appear to be a pathogen.

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Genetic spots Pathogen: None - not a disease. Signs/Symptoms: Yellow spot and flecks - sometimes with necrotic centers. Common in many inbreds - appearing similar to eyespot and sometimes associated with rust resistance genes. ID tips: If other diseases have been ruled out (i.e. - no eyespot conidia, no bacterial streaming), it probably is genetic.

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Purple leaf sheath Pathogen: None -not a disease. Signs/Symptoms: Purple blotches on the leaf sheaths after tasseling. Occurs when saprophytic fungi and bacteria develop on pollen lodged between the stalk and the leaf sheath. The stalk is not discolored.

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