Best management practices (brief overview):
*NEW*- EVALUATION OF ATOXIGENIC STRAINS OF ASPERGILLLUS FLAVUS FOR AFLATOXIN CONTROL IN CORN ON COMMERCIAL FARMS IN TEXAS - 2011.
The Office of the Texas State Chemist Releases a "One Sample Stratagy" sampling guide for aflatoxins (the handbook).
Aflatoxin, a mycotoxin produced by the fungus Aspergillus flavus, is a potent carcinogen and regulated to protect purchasers and consumers of corn. Unfortunately, there is no one "silver bullet" solution for producers or consumers to prevent aflatoxin from accumulating or being consumed. However there are steps and "best management practices" (BMP's) that producers can take towards reducing risk of aflatoxin accumulations.
Click here for a full description of best management practices for aflatoxin (.pdf).
* Hybrid selection: Choosing an adapted hybrid for your area that is least susceptible to aflatoxins will help to minimize aflatoxin risk. In many areas the fungus that makes aflatoxin is present carried to the silks by wind and rain, in these cases a Bt trait is not expected to reduce aflatoxin. Bt may help to reduce aflatoxin in the few areas where insect vectors are the main cause of Aspergillus infection.
* Planting conditions: Heat and drought stress increase susceptibility to aflatoxin. Two practices that reduce these risks are minimizing tillage to conserve moisture and planting early to reduce late season heat and drought stress.
* Atoxigenic strains (i.e. Aflaguard): A commercial product can be purchased containing Asperigillus flavus spores which do not have the ability to produce aflatoxin. These are applied to the fields just before silking, and sufficient moisture needs to be present. Results and effectiveness vary based on many factors, both excellent and poor results have been observed.
*** Click here to learn more about atoxigenic control of aflatoxin in corn (.pdf). (Extension Publication)
*** A study using on-farm trials with atoxigenics in 2011
* Pest control: Weeds compete for moisture and increase plant stress. Insects increase plant stress and may carry A. flavus spores that will infect the grain. Both must be controlled.
* Moisture: Optimize irrigation. Avoid moisture stress between flowering and grain fill. With high plant populations, extra care must be taken to avoid moisture stress.
* Fertility: Maintain optimal nitrogen fertility, especially with high plant populations.
* Field segregation: Corn from fields or portions of fields showing moisture stress should not be mixed with corn from other fields.
* Combine setting: Adjust combine ground speed and cylinder speed to minimize trash and broken kernels in hopper. This involves
operating at a slow speed, using a lower gear than normal, and then gradually increasing speed up to the point that trash and broken kernels enter the hopper. Increase fan speed to blow out immature and broken kernels.
* Grain moisture:
This is not usually done in Texas, but corn can be harvested at higher than usual moisture contents and then artificially dried. A quick drying reduces
mycotoxin accumulation that could occur in the field as the corn is drying. For example, harvest corn at 24% kernel moisture, then it dry down to 15% within 24 hours.
* Transport: If corn is harvested at high moisture with the intention of drying it later, store and transport it as quickly as possible.
* Baling corn: Whenever the hay contains ears with kernels, there is a risk of aflatoxin contamination. High levels of aflatoxin can be
present, even if no fungal growth can be seen.
*** Click here for a document on aflatoxin in baled corn (.pdf).
* Grain storage: Ensure that grain bins are properly ventilated, to minimize temperature differences. High levels of aflatoxin can be
present, even if no fungal growth can be seen.
Once corn is contaminated above certain threshold levels of aflatoxin there are only two approved methods for dealing with this: blending or destruction. Research is currently ongoing into special clays that bind aflatoxins.
Sampling and Detection
One of the most challenging problems of aflatoxin is that it is undetectable to the eyes and nose of both humans and animals. The 20ppb action level is equivalent to one quart of water in an Olympic size swimming pool ! If any green fungus is present aflatoxin is likely present, however even if no fungus is present and the grain looks clean aflatoxin may still be present. There are a variety of aflatoxin testing methods that can be used, supplied by a number of vendors. Contrary to popular myth, a black light does not detect aflatoxins !
Proper sampling of grain for aflatoxin contamination can also be an enormous issue and proper procedures should be used.
*** Click here for a document on sampling grain for aflatoxin (.pdf).
Description of best management practices for aflatoxin (.pdf).
Atoxigenic control of aflatoxin in corn (.pdf).
Aflatoxin in baled corn (.pdf).
Sampling for aflatoxin (.pdf).
Contrasts and Comparisons between Fumonisins and Aflatoxins (.pdf).
A study using on-farm trials with atoxigenics in 2011
Mycotoxins in corn (.pdf)
Narrated slides on aflatoxin in corn (Very large movie clip)
Office of the Texas State Chemist - Best Management Practices
• Aflatoxin/ mycotoxin maps