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United States Department of Agriculture

Agricultural Research Service

Title: Cyfluthrin Persistence in Soil As Affected by Moisture, Organic Matter, Andredox Potential

Authors
item Smith S Jr,
item Willis G H,
item Cooper C M,

Submitted to: Environmental Contamination and Toxicology Bulletin
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 31, 1995
Publication Date: N/A

Interpretive Summary: Information on the degradation/persistence in soil of the pyrethroid insecticide cyfluthrin is proprietary. Therefore, we investigated the persistence of cyfluthrin in soil under anaerobic conditions since such conditions frequently occur intermittently in Mississippi River delta cotton fields and south Louisiana sugarcane fields during the cool, rainy season (late fall, winter, and early spring). Cyfluthrin remaining after summer applications could be subjected to anaerobic conditions. Under the conditions of this study, cyfluthrin persistence in soil was affected by organic matter and reducing conditions (redox potential) and unaffected by moisture. The results of this study suggest that since pyrethroid insecticides such as cyfluthrin can also dissipate readily under biologically-active anaerobic soil conditions, a practical means of reducing or eliminating pyrethroid carryover from one cropping season to the next would be by flooding cropland between harvest and planting. A project involving controlled flooding of large fields in the Mississippi River delta has recently been proposed. Such controlled flooding should not only result in anaerobic soil conditions conducive to pesticide degradation but also in reduced sediment production (soil erosion) from the fields due to the water cover.

Technical Abstract: The persistence of the pyrethroid insecticide cyfluthrin [(RS-alpha-cyano- 4-fluoro-3-phenoxybenzyl(1RS,3RS)-cis,trans-3-(2,2-di-chlorovinyl)-2,2- dimethylcyclopropanecarboxylate] was studied in the laboratory under moist, anaerobic soil conditions. During the 140-d incubation period of the study, cyfluthrin disappearance was faster at lower redox potentials and in soil that had been amended with organic matter (crop residue). Soil moisture (-0.3 bar vs. -1.0 bar) did not affect cyfluthrin persistence. Estimated 50% disappearance times (DT50's) for cyfluthrin ranged from 27-39 d.

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