August 26, 2005

This year’s dry weather has already caused drought stress in some corn crops, with a serious limitation to yields in many areas. Now, University of Kentucky Plant Pathologist Paul Vincelli said producers may also want to consider the effect that drought stress can have in the production of poisonous substances called mycotoxins, particularly carcinogenic alflatoxins.

“When significant levels of aflatoxins are detected in corn, drought stress and high temperatures are typically associated with it,” he said. “Injury to kernels from insects and possibly other factors also increases the risk of aflatoxin accumulation.

Vincelli said aflatoxins, which are sometimes produced in corn by the fungus Aspergillus flavus, occur infrequently in Kentucky and often are associated with poor handling and storage. However, where drought stress has been severe, it is possible to have high levels of the toxin in corn coming right out of the field.

“An important fact to understand about aflatoxin in the Midwest is that when it occurs, the incidence and severity can be very variable,” he said. “Even in a county or portion of a county with the occasional field with high levels, you can also expect to find fields with low levels and undetectable levels.”

Vincelli pointed out that he does not anticipate substantial aflatoxin problems, however he said it’s always good to be educated about them, and an Extension publication titled Aflatoxins in Corn, ID-59, is a good resource. The publication can be read online at

The publication includes information about using aflatoxin-contaminated grain, should the toxin be detected. Aflatoxin levels in food and livestock feed are regulated by the U.S. Food and Drug Administration, which does not permit blending of grain contaminated by the toxin with clean grain for interstate commerce. Blending is only allowed for on-farm use. Vincelli recommends that if producers suspect the presence of aflatoxin that they have it tested, separate it from other grain and then feed it only to appropriate livestock, which are identified in the aforementioned publication.

“In addition to the overview in that publication, producers may be interested to know of research showing that the aflatoxin content of infected kernels rises rapidly as the kernel dries below 20 percent moisture,” Vincelli said. “Therefore, if feasible, it may be advisable to harvest drought-stressed fields before the corn drops below 20 percent moisture content and dry the grain to 15 percent within 24 hours of harvest.”

Fumonisins is another family of mycotoxins that is associated with drought in corn. Fumonisins have the potential to cause lethal diseases in horses and swine. Preharvest fumonisin contamination in corn is most often associated with drought stress at the silking stage.

“Since the fungus that produces fumonisins can grow in grain above 18.4 percent moisture, it is advisable to harvest grain at 25 to 27 percent moisture content and to dry it below 16 percent within a day or two of harvest,” Vincelli said. 

More information about fumonisins is available in the Extension publication Fumonisin, Vomitoxin and Other Mycotoxins in Corn Produced by Fusarium Fungi, ID-121. It is available on the Web at

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Editor: Aimee Nielson 859-257-4736, ext. 267
Contact: Paul Vincelli 859-257-7445, ext. 80722


Writer: Aimee Nielson 859-257-4736, ext. 267

Contact: Paul Vincelli 859-257-7445, ext. 80722