RUNOFF WATER from Mississippi fields planted with genetically engineered cotton was virtually free of insecticides during a four-year Agricultural Research Service study.

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.