Extension Ag Update
December 2008
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Pesticide Trends in Corn Belt Streams and Rivers
Ellen Phillips, Extension Educator, University of Illinois Extension, 708-352-0109,

The US Geological Survey recently released the results from the NAWQA Pesticide National Synthesis Project, which began in 1992.  It is a national-scale assessment of the occurrence and behavior of pesticides in streams and ground water of the United States.  The potential for eleven pesticides to adversely affect drinking-water supplies and up to 31 stream aquatic ecosystems were assessed for two time periods: 1996–2002 and 2000–2006.  Pesticides included in the analyses were atrazine, acetochlor, metolachlor, alachlor, cyanazine, EPTC, simazine, metribuzin, prometon, chlorpyrifos, and diazinon.

The results showed that streams in both agricultural as well as many urban watersheds almost always have 3 or more pesticides present throughout 85-90 percent of the year.  During about a fourth of the year, the streams can have nine or more pesticides in the aquatic ecosystem at one time.  This combined pesticide toxicity is a concern since there is limited research on the effects of the combined effects of pesticides verses having just one pesticide present.

Samples of groundwater also showed mixtures of pesticides, although there is less contamination than in streams.  About half of the shallow wells in agricultural areas and about one third of shallow wells in urban areas, contained 2 or more pesticides.

The study found showed that the level of some pesticides in streams decreased over the last decade.  What can we do to minimize pesticide contamination of our environment?   Many of the same methods used to prevent soil erosion and runoff also help to lower pesticide runoff.  Filter strips have proven to be quite effective at reducing pesticide runoff.  To minimize groundwater contamination, it is important to avoid soil contamination during mixing and loading of equipment.  Avoid mixing pesticides close to wells.  Installing a rinse pad or utilizing a nurse tank of water to move the mixing site to different locations are both effective ways to minimize soil contamination.  Lastly, utilizing a hose air gap or a check valve to prevent back siphoning into the water source is a simple way to protect well water. For more information about the study results go to website: http://water.usgs.gov/nawqa/pnsp.

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