October 10, 2002

LINCOLN, Neb. — With elevated levels of mold toxins showing up in corn this fall, it is important for growers to match proper management practices with the grain's end use, a University of Nebraska plant pathologist said.

Testing is the only way to determine aflatoxin and fumonisin levels in the grain, said Jim Stack, plant pathologist at NU's South Central Research and Extension Center. Molds and fungi on corn can produce mycotoxins, such as aflatoxin and fumonisin.

These toxins reduce grain quality and can be toxic to farm animals, wildlife and people, Stack said. Fumonisin is extremely toxic in horses and is a suspected carcinogen in humans. No fungicides are labeled in Nebraska for managing molds or mycotoxins in corn.

"It's not enough just to know if you have a grain mold or a fungus," he said. "Only a laboratory analysis can establish the occurrence and concentration of mycotoxins which will determine how the grain should be managed and its implications of marketing the grain."

The level of contamination is key in determining how the grain can be used. For example, corn that would not be safe for human consumption could be fed to finishing beef cattle.

Federal Food and Drug Administration tolerances for aflatoxin are: 0.5 parts per billion for milk; 20 parts per billion humans, immature animals and for dairy; 100 parts per billion for mature breeding cattle, swine and poultry; 200 parts per billion for finishing swine weighing over 100 pound and 300 parts per billion for finishing beef. The FDA tolerances for fumonisins are: 5 parts per million for horses, 10 parts per million for swine and 50 parts per million for cattle.

In Nebraska, grain molds occur every year to varying degrees in corn, Stack said, but this season's drought stress coupled with rains in parts of Nebraska created ideal growing conditions for the fungi.

Even irrigated corn may have the potential for contamination because many farmers had trouble keeping up with the their crop's water needs.

Since mycotoxins are not evenly distributed in fields, a representative sample of no less than 5 pounds of corn in a paper bag should be delivered or mailed to a laboratory for testing. Moldy grain can be tested at a private toxicology lab or the Veterinary Diagnostic Center at UNL.

The Nebraska Department of Agriculture's blending policy and intrastate commerce regulations do not object to blending corn with higher levels of aflatoxin with corn containing little or no aflatoxins if the corn is intended as animal feed for finishing beef cattle or finishing swine weighing more than 100 pounds, said Ken Jackson, program manager for the feed and fertilizer section at the department.

The department's interstate commerce blending policy also does not object to blending corn with aflatoxin levels above 300 parts per billion and corn with little or no aflatoxin if the corn is intended for beef finishing feed.

The producer or user is required to test the finished blend to verify the aflatoxin levels in the blended corn do not exceed 300 parts per billion for finishing beef cattle or 200 parts per billion for finishing swine weighing more than 100 pounds. Test results should be kept for at least a year, Jackson said.

Shippers and sellers also must provide a label or invoice stating the level of aflatoxin in the blend, designate on the invoice or label what livestock species will be fed the product and have some assurance that the buyer is aware of the level and will use it accordingly, he said.

Grain handlers should use caution and wear dust masks when moving or processing grains, Stack said. It is recommended that workers wear a respirator when working in silos or other enclosed areas containing grain.

Breathing grain molds can cause acute allergic responses or chronic allergic response. Mold can cause serious disease in people with lowered immune systems. Symptoms in humans include: suppression of the immune system, reproductive dysfunction, cancer and death. Animals symptoms include: feed refusal, short-term illness, reproductive dysfunction and death.

An NU Cooperative Extension video-conference featuring information on testing and management of aflatoxin and fumonisin in corn, including field and storage management, blending and feed additives is archived on the Web at "Market Journal" or Crop Watch.

For more information on grain molds, including how to identify the different types and their effects, consult NU Cooperative Extension NebGuides G00-1408-A, Grain Molds and Mycotoxins in Corn, or G87-850-A, Understanding Mold Toxins, both available at local Cooperative Extension offices and on the Web.

Cooperative Extension is in NU's Institute of Agriculture and Natural Resources.

10/10/02-SA

Jim Stack
Plant Pathology
Extension Plant Pathologist
(402) 762-4435

Sandi Alswager Karstens
IANR News and Photography
(402) 472-3030

Department: Plant Pathology