Across the Corn Belt from Ohio to Colorado, grain quality experts and Extension staff are warning corn growers to be alert for Gibberella ear rot infections and the resulting potential for vomitoxin (deoxynivalenol or DON) and zearalenone mycotoxins in stored corn.
This is when thorough scouting for ear rot at the black-layer stage pays off, says Alison Robertson, an assistant professor of plant pathology at Iowa State University.
“Producers need to be thinking about any corn they harvested from fields where there was a mold problem,” says Robertson.
“My concern is that (infected corn) is sitting in storage. If you don't manage it well, you get hot spots where mold will continue to grow and potentially produce mycotoxins,” he says.
Robertson notes that keeping moisture levels below 15% and keeping corn cool will help slow fungal growth and mycotoxin potential, but says contaminated corn just won't store well for very long.
Ear mold pathogens like Gibberella are always present in the soil. In 2009, the wet weather many areas experienced when corn was silking and rains during a delayed harvest both favored Gibberella infection and growth.
HAIL DAMAGE CAN also be a factor in ear mold development and the potential for vomitoxin and zear-alenone, she says.
“We have (Gibberella) all over Indiana, and it's really critical in the northern part of the state,” says Charles Woloshuk, Purdue University professor of plant pathology.
One option for farmers with mold problems is to clean the corn, which breaks up diseased kernels so they end up as fines, according to Woloshuk. “You can get rid of a lot of contaminated material and get levels down by doing that,” he says.
Both Robertson and Woloshuk emphasize the importance of testing questionable corn before feeding it to livestock and of exercising special care when feeding swine, which may show symptoms from contamination at levels as low as one part per million (ppm).
“If you're feeding, you have to know the numbers so you're not in a toxic range,” says Wolochuk. “You can't afford to rely on trial and error.”
Symptoms associated with vomitoxin include vomiting, decreased weight gain, diarrhea, lethargy, blanched skin color, dermal irritation, hypothermia, intestinal hemorrhage and feed refusal. Zearalenone can trigger reproductive problems, including infertility and abortion.
“If you must feed corn with high levels, your best bet is finishing cattle,” he says. “You can also blend with uncontaminated corn.”
Unlike aflatoxin, there is no Food and Drug Administration (FDA) action level for DON and zearalenone, but FDA has issued an advisory level of 5 ppm in grain or processed grain products such as corn gluten meal and distillers' grains.
Corn processors are alert to mycotoxin concerns in the 2009 crop, according to Geoff Cooper, vice president for research at the Renewable Fuels Association. Cooper says ethanol plants have stepped up their mycotoxin testing beyond normal levels in parts of Ohio, Indiana and Illinois where mycotoxin concerns are most common.
“Ethanol plants are letting their suppliers know what the maximum level is that they will accept,” he says. “That will commonly be the FDA advisory level divided by three because of the way mycotoxins concentrate in the feed fraction.”