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Protecting Peanuts from
Aflatoxin
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Peanut plant.
(K7798-5)
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Peanut farmers could soon
have a biological pesticide for protecting their crop's prized seed from fungi
that produce aflatoxin—the chief culprits being Aspergillus flavus
and A. parasiticus.
Circle One Global, Inc. (COGI), of Cuthbert, Georgia, has
applied for an exclusive license on an ARS technique for making the biopesticide
from spores of a nontoxigenic, or benign, strain of A. flavus.
In Florida, Georgia, and Alabama—top peanut-producing
states—aflatoxin outbreaks from 1993 to 1996 caused losses averaging $26
million annually, ARS economist Marshall C. Lamb estimates. The Peanut
Administrative Committee strictly regulates the sale or use of shelled peanuts
having above 15 parts per billion of aflatoxin. Those peanuts can't be used in
edible products, and shellers receive a much lower price for them.
Currently, there's no direct action peanut farmers can take
to control fungi that produce aflatoxin. But ARS researchers are hoping to
change that by helping COGI commercialize a biopesticide that peanut farmers
can apply to their fields.
The approach is known as biocompetitive exclusion, explains
Joe W. Dorner, a microbiologist in charge of the project at ARS' National
Peanut Research Laboratory, in Dawson, Georgia. It involves formulating the
benign mold's spores and seeding them into soils around peanut plants. There,
by colonizing the peanut pod zone, the mold becomes a living shield against
toxigenic fungi.
It may sound simple, but Dorner and ARS colleagues spent 14
years developing the technology and researching ways to make it commercially
feasible.
One of the biggest challenges was finding a fast, cheap way
of mass-producing the biopesticide. Initially they tried solid-state
fermentation, which involves growing the spores on a substrate of rice or
another grain. But this proved expensive and time-consuming. Also, the
substrate required sterilizing and drying before packaging.
In 1999, they switched to mixing the spores with soybean
oil, then spraying them onto whole, hull-free barley kernels. Coated with
diatomaceous earth, which is self-drying, the kernels become tiny, easily
applied granules.
Not only does the simplified method eliminate costly
machine-drying and sterilization, but it can also churn out several tons of
product per hour at a minimum of raw-material costs per pound of product.
“This barley formulation serves as both a carrier to
deliver the fungus and a substrate on which it can grow and produce spores that
penetrate the soil,” Dorner explains. In fields tests, applying the
formulation at a rate of 20 pounds per acre curbed aflatoxin levels by 70 to 90
percent compared to untreated, control plots.
COGI plans to register the formulation as a biopesticide
with the U.S. Environmental Protection Agency. Once registered, the product
could become commercially available in the next couple of years, says COGI
spokesman Ronnie Balkcom.—By
Jan Suszkiw,
Agricultural Research Service Information Staff.
This research is part of Food Safety (animal & plant
products), an ARS National Program (#108) described on the World Wide Web at
http://www.nps.ars.usda.gov.
Joe W.
Dorner and Marshall C. Lamb are
with the USDA-ARS National Peanut Research
Laboratory, P.O. Box 509, Dawson, GA 31742; phone (229) 995-7408, fax (229)
995-7416. |
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"Protecting Peanuts from Aflatoxin" was published in the
January 2002
issue of Agricultural Research magazine. |
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