Reduced in Runoff from Bt Cotton
By Hank Becker
March 7, 2001
Runoff water from Mississippi fields
planted with genetically engineered cotton was virtually free of insecticides
during a four-year Agricultural Research
To measure pesticide runoff, the scientists planted cotton that was
genetically engineered to contain a toxin from the bacterium Bacillus
thuringiensis. Researchers planted the Bt cotton near Beasley Lake in
Sunflower County--one of three watersheds within ARS Mississippi Delta
Management Systems Evaluation Area project. Because Bt cotton produces its own
insect-inhibiting toxin, less pyrethroid insecticide is needed to control
budworm and bollworm infestations.
From 1996 through 1999, agricultural engineer Robert F. Cullum and chemist
Sammie Smith with ARS National Sedimentation
Laboratory, Oxford, Miss., analyzed runoff samples for insecticides from
both Bt cotton and non-Bt cotton fields. They looked especially for pyrethroids
and organophosphates because of their widespread use throughout the
7,000-square-mile, cotton-producing area.
The fewer pyrethroid applications needed on Bt cotton sites reduced the
amount of pesticides released into the environment. And while runoff from
non-Bt cotton sites contained very slight amounts of pyrethroid insecticides,
runoff from Bt cotton sites had almost none at all.
The team found only insignificant amounts of organophosphate insecticides
used to control boll weevils in runoff from either the Bt or non-Bt cotton
sites. The scientists concluded that there are no detrimental environmental
effects from either pyrethroid or organophosphate insecticides in runoff from
any of the watershed sites sampled during this study. The finding will be
useful to extension workers, action agencies involved in water-quality
planning, and farmers interested in reducing insecticide applications while
maintaining control of pest infestations in their cotton crop.
ARS is the chief scientific research agency in the
U.S. Department of Agriculture.
Scientific contact: Robert F. Cullum, Water Quality and Ecological
Processes Research Unit, ARS National Sedimentation Laboratory, Oxford, Miss,
phone (601) 232-2976, fax (601) 232-2915,