The U.S. Geological Survey said declines in pesticide concentrations closely followed declines in their annual applications. That, said researchers, suggests reducing pesticide use is an effective and reliable strategy for reducing pesticide contamination in streams.
Scientists studied 11 herbicides and insecticides frequently detected in the Corn Belt region, which generally includes Illinois, Indiana, Iowa, Nebraska and Ohio, as well as parts of adjoining states.
The USGS said that area has among the highest pesticide use in the nation -- mostly herbicides used for weed control in corn and soybeans.
The study is based on analysis of 11 pesticides for 31 stream sites in the Corn Belt for two partially overlapping time periods: 1996 to 2002 and 2000 to 2006. Pesticides included in the trend analyses were the herbicides atrazine, acetochlor, metolachlor, alachlor, cyanazine, EPTC, simazine, metribuzin and prometon, and the insecticides chlorpyrifos and diazinon.
The report and additional information is available at http://water.usgs.gov/nawqa/pnsp/.