Drought brings potential for aflatoxin
By Jean Caspers-Simmet
Date Modified: 09/10/2012 3:09 PM
NASHUA, Iowa —The persistent drought brings the potential for aflatoxin in corn, says Connie Hardy with Extension's Grain Quality Initiative told farmers during a fall field day at the Northeast Research Farm at Nashua.
Hardy urged farmers to scoutand if they suspect they have it, contact their crop insurance agents about steps to take when testing and harvesting.
Aflatoxins are chemicals produced by fungi Aspergillus flavus. The fungi can be recognized by olive green or gray-green mold on corn kernels.
"While aflatoxin is not automatically produced whenever grain becomes moldy, the risk of aflatoxin contamination is greater in damaged, moldy corn," Hardy said.
Aflatoxins are harmful or fatal to livestock and are considered carcinogenic to animals and humans.
"Alfatoxin levels are highest during hot, dry summers," Hardy said. "The prime conditions for the fungus to produce toxin are hot, dry weather during pollination and grain fill, and warm nights (above 70 degrees) during later stages of grain fill in a period of drought."
Grain elevators and processors will screen for aflatoxin this fall, Hardy said. Rapid, on-site tests can determine its possible presence, but they don't provide specific quantitative results. The toxins are produced inside kernels and their presence is best determined by specific analytical laboratory tests.
The Food and Drug Administration has established an "action level" of 20 parts per billion for aflatoxins in corn in interstate commerce.
"This is the level at which federal agencies may take action, including seizure of the corn or prohibition of its sale," Hardy said. "Elevators do not accept corn with 20 ppb or more of aflatoxin unless they have a known use."
The FDA has guidelines for acceptable aflatoxin levels in corn based on intended use, Hardy said. These are based on maintaining performance and avoiding disease, except for dairy cattle in which prevention of aflatoxin residue in milk is the concern. Pet food is also a concern because of the greater sensitivity of dogs and cats to aflatoxin.
As kernel moisture decreases, aflatoxin production increases, Hardy said. Toxin production is highest at 20 percent to 18 percent kernel moisture and stops at around 15 percent moisture.
Farmers should scout for aspergillus ear rot from dent through to harvest at five to 10 locations in a field, targeting areas with plants that appear most stressed, Hardy said. At each location, peel back the husks of 10 ears and inspect them for olive-green powdery mold. If greater than 10 percent of the ears show aspergillus ear rot, schedule the field for early harvest.
Early harvest and sampling should be coordinated with crop insurance adjusters, Hardy said. If the adjuster hasn't visited the field before harvest, follow agents' advice on leaving strips in the field.
Corn contaminated at levels greater than 20 parts per billion may not be sold for interstate commerce, Hardy said. However, most grain can find a safe and legitimate use.
Producers who receive a crop insurance settlement based on aflatoxin must document that the aflatoxin corn is used according to FDA feeding guidelines.
Blending aflatoxin-contaminated grain with clean grain is illegal except in advance of direct feeding, and blended grain may not be sold in general commerce.
Since aflatoxin is concentrated (three times those in whole corn) in ethanol co-products like distiller's grains, processors may not accept corn with aflatoxin if they market their products to dairy producers, for pet food or for exports, Hardy said.