Aflatoxin is about the dirtiest non-four letter word there is  (pardon me while I wash out my mouth and sanitize the keyboard.)  It is just as prevalent as reality TV shows and political attack ads, and carries about the same value. 

Nevertheless, it is in your corn, thanks to the environment, and many elevator managers are holding their nose, crossing their fingers, and praying that you didn’t have any in the load you just dumped.  Others are spot checking, some are testing most loads, and some are rejecting loads of corn because of the high contamination.  And many (possibly most) farmers are oblivious of the problem and are storing contaminated corn in their bins, where the concentration can increase.  What do you need to know and do?  Here is some help…

What does it look like?

Aflatoxin: What a way to end the yearIf you find corn with an olive-green mold, you have corn with the fungus known as aspergillus ear rot, which over time and with the correct moisture will produce aflatoxin, a cancer-causing agent.  Corn with aflatoxin can be rejected at grain elevators because it could get into the food chain, and it can be rejected at ethanol plants, where it will be concentrated in the DDGS’,  preventing its use as a livestock feed.   When rejected, whether at an elevator, processor, or feedlot, the producer may have a truckload of contaminated corn, which no one wants, along with the 100,000 more bushels of corn in the grain bin at home.

So, how do you know if you have it, before you harvest it and cannot do anything with it?  The first answer is to scout your fields and look for aspergillus.  The University of Nebraska suggests that “Ear rot diseases and aflatoxin are not evenly distributed across fields or in the grain, so scouting and/or sampling should include a substantial portion, at least several acres. The presence of the fungus in kernels does not always correlate well with the presence of aflatoxin, nor does the absence of visible fungal growth necessarily indicate the absence of aflatoxin.

  • Open husks to view a large number of ears.
  • Look for the presence of dusty yellow-green to olive-green spores, especially on the surface of damaged kernels or ear tips (Figure 1).
  • Pay special attention to higher risk areas., such as drought-damaged fields, including (dryland) fields and non-irrigated pivot corners; fields or areas with higher incidence of corn ear-feeding insects, such as the corn ear worm; and grain damaged before or during harvest or after harvest while in storage.

I have it, now what?

If you have harvested grain with aspergillus, and potentially contaminated with aflatoxin, ensure that you dry the grain to less than 15% moisture within 48 hours after putting it in the bin, and preferably to 13% moisture or less, which retards the production of aflatoxin by the aspergillus mold.

If you have corn that is contaminated and rejected by the elevator, your first choice of feeding it to livestock is a non-starter.  The Food and Drug Administration has established the following maximum limits for aflatoxin in food or feed, and exceeding these limits will put the health of the animal in jeopardy, along with the humans who may consume products from that animal.

Commodity Action Level


Finishing (feedlot) beef cattle


Finishing swine of 100 pounds or greater


Breeding beef cattle, breeding swine, or mature poultry.


Immature animals and dairy cattle


For animal species or uses not otherwise specified, or when the intended use is not known


Human food


Here is your job:

For uncertainty about whether you have aflatoxin in your corn, check your fields and test samples for aflatoxin.  University of Nebraska has produced a guide on sampling and testing for such molds in grains and feed. 

After selecting some samples of grain which are potentially contaminated, they must be sent to an approved laboratory where aflatoxin can be confirmed if it is present and you have the basis for a crop insurance claim due to the contamination.  USDA’s Risk Management Agency has provided an incomplete list of laboratories for testing.

Crop insurance policies will indemnify producers who have an aflatoxin problem, but the grain must still be in the field.  Any contaminated grain that has crossed the head of a combine will not be reimbursed for loss.  If an adjustor has not inspected your claim by the time it needs to be harvested, call your insurance agent to find out the details of leaving a four row strip every 10 acres.  For details on what the adjustor will look for is detailed on this fact sheet from the risk management agency.


Aflatoxin not only can destroy any value there is in stored grain, but also cause cancer in animals and humans that consume it.  Subsequently, farmers and other members of the food chain must keep it out of the grain pipeline.  When elevators, grain processors, and feedlots refuse to accept contaminated corn, there is little that can be done with it, short of burying it.  However, crop insurance will indemnify a farmer with contaminated grain, if the grain remains in the field and can be tested by the adjustor.

Source: FarmGate blog