|Southwick Jr, Lloyd|
|Rebich, Richard - US GEOLOGICAL SURVEY|
Submitted to: Mississippi Water Resources Research Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: February 9, 2000
Publication Date: N/A
Interpretive Summary: The Mississippi Delta Management Systems Evaluation Area comprises three oxbow lake watershed study sites near Greenwood, MS. The study is designed to measure the effectiveness of a variety of conservation practices such as filter strips, slotted board risers, conservation tillage and natural riparian zones on runoff losses of agricultural chemicals into the oxbow lakes. The samples have been analyzed for organophosphate and pyrethroid insecticides over this 4-year period. No detections of the organophosphate and only 2 detections of pyrethroids have been made. Part of the reason for few detections of the pyrethroids has been the low application rates of these compounds. Unfortunately, in each of the 4 seasons few runoff events occurred during the first 30 days after application when runoff of applied agricultural chemicals is most likely. Consequently, there have been too few data to adequately test the efficacy of the various conservation practices in the watersheds for reducing runoff losses of the insecticides
Technical Abstract: Runoff samples from the Mississippi Delta Management Systems Evaluation Area (MDMSEA) were collected and analyzed for pyrethroid (lambda cyhalothrin, cypermethrin, and cyfluthrin) and organophosphate (methyl parathion and azinphosmethyl) insecticides over a four-year period (1996 through 1999). Over this period only two detections were made for the pyrethroids: in the 1999 season, 20 ppt lambda cyhalothrin was measured 10 days after application (DAA), and cypermethrin was observed at 100 ppt at 6 DAA. Part of the reason for so few detections of the pyrethroids is the low application rates of these compounds: 80 mL/ha (1 oz/ac). No detections of the organophosphates were made during the 4-year study period. These results have not been a good test of the various conservation practices of MDMSEA, since runoff events were infrequent, especially during the first 30 DAA when detections in runoff are most likely. Conservation practices for water quality preservation with respect to pesticide use are most valuable for the first few weeks after application.