Early harvest reports regarding corn coming from fields in certain areas of Iowa and other parts of the Midwest where drought hit hard this summer are confirming that there is some incidence of aflatoxin in the 2012 corn crop. "The highest potential is in areas of extreme drought and in cases where August storms put corn on the ground," says Charles Hurburgh, an Iowa State University grain quality expert.
Hurburgh, a professor of ag and biosystems engineering, was interviewed by Wallaces Farmer regarding the aflatoxin situation. In this following article, we've divided the topic into three sections:
1) Testing corn for aflatoxin: What you need to know to avoid sampling errors
2) Handling corn that has aflatoxin detected: What you need to know to direct corn with aflatoxin to appropriate uses
3) Crop insurance questions regarding aflatoxin: What you need to know about making a claim to your insurance agency
There are also three earlier articles on ISU's ICM News online which described the biology and the impact of aflatoxin on the grain market:
* Aflatoxin Detected in Fields in Central and Southern Iowa
* Crop Quality Issues from the Drought of 2012
* Aspergillus Ear Rot and Aflatoxin Production
The most sensitive corn users will be dairy, pet food, direct human consumption (snack foods, etc.) and processors that either export or sell some products to sensitive uses. Ethanol plants and corn wet mills, as a result of the processing of the corn grain, concentrate the toxin in their protein coproduct.
Many ethanol plants export distillers grains, or DDGS, as well as sell to local feed markets. If corn comes into an ethanol plant containing 10 parts per billion of aflatoxin, the aflatoxin is concentrated by a factor of three in the distillers grains. Thus, the distillers grains end up with 30 ppb of aflatoxin. Hurburgh offers the following information and recommendations regarding aflatoxin.
Testing corn grain for aflatoxin: Steps to take to avoid sampling errors
Aflatoxin: Testing Corn -- Testing for aflatoxin is very challenging because of very high sampling error. Individual kernels can contain up to 400,000 parts per billion. With the typical weight of a kernel, one very high kernel in a 5-pound sample will cause the sample to be about 52 ppb.
This individual kernel effect is why large samples and grinding of entire samples is necessary to get useful results. If the sample with the very high kernel were divided as whole corn to get 1/20th for the actual analysis, there would be 19 possible divisions with none and one that would test over 1,000 ppb!
The more grain is moved and mixed the more homogenous the aflatoxin will become. Samples taken farther down the grain distribution chain are, in general, more accurate, but action to control problems is more complicated after the first point of delivery.
Samples should not be divided as whole kernels to reach the smaller size needed for testing. A minimum of 5 pounds is required to have statistical validity; even then the sampling error for aflatoxin testing is 25% to 40%.