David Gibson, executive director of the Texas Corn Growers Association, recently spoke to a crops clinic in Bell County about what we know now about aflatoxin and what is still a mystery. It was an appropriate setting because Bell County has been one of the counties hardest hit by high levels of aflatoxin.
“A few years ago I spent a lot of time with growers in Bell County over aflatoxin,” Gibson said a few days after the presentation. “Fortunately for them, they haven't had as much use for me the last few years.”
There have been fewer reports of aflatoxin over the last three years and fewer complaints about how it is tested, which is sometimes blamed for high levels in any given batch of corn. Gibson believes that atoxigenic products like Afla-Guard and A-36, along with new heat and drought resistant varieties, better management practices and a better sampling process have combined to lower the levels.
Aflatoxin is a fungus that can grow on corn. It is a carcinogen and can be fatal in sufficient quantities. The U.S. Food and Drug Administration (FDA) mandates that corn for human use or for use as dairy feed contain no more than 20 ppb (parts per billion) of aflatoxin. Corn for the feedlot industry can test as high as 300 parts per billion. Corn that tests at 500 ppb or higher must be destroyed.
Afla-Guard and other bio-control products contain a naturally occurring non-toxic fungus that attacks the aflatoxin fungi. When applied at the right time and under the right conditions, the atoxigenics can out-compete the toxic spores with non-toxic spores that basically crowd the toxic ones out.
Heat and drought-tolerant varieties also seem to have lowered levels of aflatoxin, and management practices like breaking up hardpan, minimizing tillage and planting at an optimum time all help reduce the incidences of aflatoxin.
“I want to say that, yes, levels are down, but that's hard to quantify,” Gibson said. “We still have some hot spots that show up despite everything.”
The “One Sample Strategy” of testing has also helped by offering a more reliable and standardized method of testing for aflatoxin, Gibson said. The Office of the Texas State Chemist (OTSC) has regulatory authority over corn with aflatoxin levels higher than 20 ppb.
Texas state chemist Tim Herrman and his staff developed the One Sample Strategy in response to tests for aflatoxin that sometimes varied widely from the grain elevator, crop insurance personnel and the OTSC. Sometimes the results even varied from one elevator to the next. The testing techniques were first approved by the Risk Management Agency in 2011 and received continuous approval last year.
Facilities that sign on are trained and recognized as approved laboratories for One Sample testing. The approved facilities use validated aflatoxin test kits and follow a precise procedure from collection through final testing. The test covers the testing at the elevator and offers official OTSC Certificates of Analysis for insurance claims. The result is the official result and eliminates the need for the other two tests.
“It has really improved the quality of testing at local sites,” Gibson said. “Sometimes you would get to the elevator and they would do a bucket scoop right off the top, or they would hold a bucket under it while it was being poured, and they would test that.
“Every place did it differently. You might have one kind of test at the elevator, another kind at the state chemist's office, another one for the insurance companies.”
Gibson said the apparent improvements in testing, varieties and control, along with some improvement in the weather in some parts of the state, have helped calm the aflatoxin storm to a degree, but he emphasized that it's still a threat, even to farmers who grow resistant varieties and use bio-controls.
“Some of the fields where it (aflatoxin) has been real bad have been treated with Afla-Guard and they are growing the resistant varieties, but they still get some really high levels. It's still a mystery. There's still a lot of research to be done.”
More information on aflatoxin and the One Sample Strategy is available on the OTSC website at otscweb.tamu.edu. The link to the One Sample Strategy website includes a list of approved facilities.