- What are mycotoxins?
- What mycotoxins occur in corn?
- What are the toxic effects of mycotoxins?
- What are the safe levels for mycotoxins in food and feed?
- When should I test for mycotoxins?
- How do I scout to determine if there is a mycotoxin problem that requires testing?
- What are the options available for mycotoxin testing?
- Will drying, heating, freezing, or other chemical methods reduce mycotoxin levels in grain?
1. What are mycotoxins?
Mycotoxins are natural chemicals produced as by-products by fungi. In general, mycotoxins are extremely stable, and dryer heat and freezing will not significantly degrade them. Exposure to mycotoxins, especially through consumption of contaminated food, can have detrimental health effects to both humans and animals. This poisoning, called mycotoxicosis, manifests itself through many symptoms, including reduced weight gain, cancer, or death. In many cases, the immune system is affected by the mycotoxin, which complicates symptom diagnosis.
2. What mycotoxins occur in corn?
There are five major mycotoxins associated with ear rot diseases of corn. Aflatoxins are found in corn with Aspergillus ear rot. Deoxynivalenol and zearalenone are found in corn with Gibberella ear rot, and fumonisins result from Fusarium ear rot. Ochratoxin is produced in corn ears infected by Penicillium verrucosum, but some Aspergillus species also produce this mycotoxin.
3. What are the toxic effects of mycotoxins?
|Mycotoxins||Corn Disease||Other Host||Toxin Effects|
|Cottonseed, tree nuts, peanuts||Hepatotoxicity, cancer, immunosuppression|
|Sorghum||Hepatotoxicity, cancer, pulmonary edema, leukoencephalomalacia|
|Wheat, barley||Gastrointestinal toxicity, inflammation of central nervous system|
|Wheat, barley, coffee, grape juice||Nephrotoxicity, cancer|
4. What are the safe levels for mycotoxins in food and feed?
For several of the mycotoxins, the U.S. Federal Drug Administration (FDA) has published “Action” and “Advisory” levels. Exceeding an Action Level limit can lead to enforcement action that assures the destruction of the contaminated product. Acceptable mycotoxin levels are most often set at the point of sale and in contract specifications. Corn that is exported must meet the import limits set by each country, which are often more stringent that the U.S.
There are five major mycotoxins associated with ear rot diseases of corn. Aflatoxins are found in corn with Aspergillus ear rot. Deoxynivalenol and zearalenone are found in corn with Gibberella ear rot, and fumonisins result from Fusarium ear rot. Ochratoxins are produced in corn ears infected by Penicillium verrucosum, but some Aspergillus species also produce the mycotoxin.
US FDA action and advisory levels
5. When should I test for mycotoxins?
Mycotoxin testing should occur if field scouting indicates there is an ear rot problem present, and grain will be used for food, animal feed or for ethanol processing.
6. How do I scout to determine if there is a mycotoxin problem that requires testing?
Corn fields should be scouted for ear rot diseases at kernel maturity (black layer) and just before harvest. Pay close attention to areas of the field where the crop may be stressed or exposed to extreme environmental conditions. These include hillsides where drought stress may be more severe (for Fusarium and Aspergillus ear rots) and low areas where moisture from fog or high dew conditions prevail (for Gibberella ear rot). When scouting, randomly select plants and examine the ear. When a diseased ear is found, at least 10 ears on adjacent plants should be examined and the following questions should be answered:
- What ear rot disease is present?
- How severe is the disease on the ear?
- What proportion of the crop is affected?
When to test for mycotoxins
The risk of mycotoxins in harvested grain will increase as the proportion of diseased ears (kernels) increases. You should assume that diseased kernels contain mycotoxins. However, mycotoxin levels may vary among diseased ears. Therefore, making the decision to test / not to test for mycotoxins is difficult. The threshold for deciding to test for aflatoxin should be very low. If you find ears with Aspergillus ear rot, you should consider testing the harvested grain for aflatoxin. For Gibberella and Fusarium ear rots, test for DON and fumonisins when 30% of ears examined in a field have ear rot or when several ears observed have high disease severity (majority of the ear is covered with mold)
7. What are the options available for mycotoxin testing?
Mycotoxin concentration in corn can be assessed by several different technologies, but analyzing mycotoxins can be a challenge due their complex nature. It is important to not rely solely on visual methods, such as the blacklight test, for confirmation of mycotoxins. In fact, in some states it is illegal to use the blacklight to reject corn at the point of sale. Visual test results can be inconsistent, and therefore samples should be sent to professional laboratories for analysis.
- Click here to view a video on the blacklight test for aflatoxin detection
- Click here for approved Midwest testing facilities for aflatoxin
Several companies (listed below) sell kits for detecting and measuring each of the mycotoxins.The cost of a single test for one grain sample and one particular mycotoxin is usually less than $10, and the equipment cost for quantification will cost approximately $3000.
Professional testing labs
Local laboratories and grain inspection services may provide mycotoxin testing service for individual corn samples. The following is not a complete list of all grain testing providers. Please check with your local Extension personnel for a more complete list of grain testing facilities in your area as the cost of mycotoxin analysis and sample submission procedures will vary by provider. Please see the following sites for specific provider information.
Arcadia, WI www.dairylandlabs.net
Memphis, TN www.balabs.com
Holmes Laboratory, Inc.
Minnesota Valley Testing Laboratories, Inc.
New Ulm, MN 56073-0249
Trilogy Analytical Laboratory, Inc
Washington, MO 63090
Indiana Animal Disease Diagnostic Laboratory (ADDL)
West Lafayette, Ind.
Indiana Crop Improvement Association
8. Will drying, heating, freezing, or other chemical methods reduce mycotoxin levels in grain?
NO. Mycotoxins are extremely stable and cannot be reduced within kernels by chemical means. In some cases, cleaning grain to remove broken grain (fines), foreign materials, and lightweight moldy kernels can remove grain and fines that have higher levels of mycotoxins, thus reducing the overall mycotoxin level of the grain.
Properly drying corn to moisture levels below 15 % will stop the growth of mycotoxin-producing fungi. The risk of aflatoxin accumulation and ochratoxin increases when moisture levels exceed 16 %. Above 18 % the risk of deoxynivalenol, zearalenone, and fumonisin increases. Warm conditions will accelerate the rate of spoilage and mycotoxin accumulation. There is no evidence of mycotoxins continuing to increase if grain is stored at appropriately low moisture.
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