Patrick E. Lipps and Dennis R. Mills
The Ohio State University
Crazy top can be found throughout Ohio but rarely causes substantial losses. The disease develops where soils have been saturated for 24 to 48 hours soon after planting.
The most characteristic symptom is the proliferation of leafy structures from the tassel and/or ears, thus the name "crazy top." In many cases, leafy protrusions occur in only the ears resulting in a mass of strap-like leaves protruding from the ear zone. Affected plants may also have profuse tiller development.
Crazy top is caused by the soil borne fungus, Sclerophthora macrospora. This fungus attacks all types of corn and a number of wild grasses. After the fungus infects, it grows systemically within the plant and may be detected in all the above ground tissues of the diseased plant.
The crazy top fungus overwinters as oospores either within infected residue or in the soil. During periods of flooding the oospores germinate and swimming spores (zoospores) are produced. The zoospores infect the growing point of the young corn plants usually before the second or third leaf stage. The fungus then grows systemically within the plant and develops in the rapidly growing tissues. The systemic growth causes a hormonal imbalance, which initiates the proliferation of leafy tissue in the tassels and ears.
No highly effective control measures can be recommended for crazy top. Very little is known about the level of resistance in corn hybrids to this disease. Proper soil drainage will reduce the risk of flooding and subsequent infection. Avoid planting corn in low wet spots where the disease is known to occur. Seed applied fungicides will not control crazy top.
Additional information is available from your local Extension office or The Ohio State University web site Ohioline at: http://ohioline.osu.edu
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Keith L. Smith, Associate Vice President for Ag. Adm. and Director, OSU Extension.
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