Watch for Moldy Corn

November 16, 2009 12:48 PM

Source: University of Minnesota Extension Service

The late harvest, wet weather and high moisture corn have contributed to reports of moldy corn across the state, and producers should pay careful attention before handling, storing or feeding the crop to livestock, University of Minnesota Extension experts warn.

 "If the corn is not harvested and dried properly, various fungi may continue to grow," said Extension plant pathologist Dean Malvick. "Both types of mold—superficial growth on the surface of the kernels and significant ear and kernel rots—may cause greater problems."

"Both molds and the mycotoxins produced by molds can cause health problems in livestock," said Extension livestock specialist Jim Linn. At heightened risk for mold and mycotoxin health and disease problems are young animals, breeding animals and lactating dairy cows, with swine and poultry species more susceptible to these problems than ruminants. Mycotoxins in large doses can cause acute health, reproduction and production problems. However, the most likely scenario with feeding of moldy and/or mycotoxin containing feeds is a higher incidence of general, chronic health problems, poor reproduction and overall poor animal growth or milk production. 

"In general, livestock producers should avoid feeding grain or grain silages containing colored molds (pink, blue green)," said Linn. Mycotoxins, on the other hand, are not visible and their presence depends on the type of fungus present and the storage environment. Livestock producers should test grains and silages for mycotoxins before feeding.   

To diagnose and help identify mold and kernel infection, producers can send samples to the University of Minnesota Plant Disease Clinic. For more information on the clinic and how to submit a sample, visit

"Diagnosis and identification can help clarify the problem and reduce it," Malvick said, "but harvest and drying may be part of the solution."

If producers are experiencing pre-harvest mold problems, 2009 is not a good year to use slow- or low-temperature drying methods, warns Extension agricultural engineer Bill Wilcke.

"Under these types of conditions, higher temperature drying methods that reduce the moisture content of the grain within a few hours or a few days are preferred," Wilcke said.

Higher temperature dryers aren't likely to run hot enough to kill the molds, he explains, but they do slow mold growth by reducing the grain's moisture content. The agitation of the grain during high-temperature drying is also likely to rub off some kinds of molds.

For more detailed information on drying and other research-based resources dealing with late harvest challenges, visit the Extension site,

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