Mobility and dissipation of ethofumesate and halofenozide in turfgrass and bare soil

The effect of turfgrass cover on the leaching and dissipation of ethofumesate and halofenozide was studied. Sampling cylinders (20 cm diam. × 30 cm long) were placed vertically in plots of creeping bentgrass (Agrostis palustris Huds.), tall fescue (Festuca arundinaceae Schreb.), or bare soil. ethofumesate [(±)-2-ethoxy-2,3-dihydro-3,3-dimethylbenzofuran-5-yl methansulfonate] was applied at 840 g ai ha^-1 on September 21, 1997. Halofenozide (N-4-chlorobenzoyl-N′-benzoyl-N′-tert-butylhydrazine) was applied at 1680 g ai ha^-1 on August 30, 1998. Replicate sampling cylinders were removed 2 h after treatment and 4, 8, 16, 32, and 64 days after treatment. Sampling cylinders were sectioned by depths and soil extracts were assayed by HPLC with a pesticide detection limit of 0.01 mg kg^-1. Turfgrass was divided into verdure and thatch and analyzed separately. ethofumesate leaching in turfgrass was reduced by at least 95% compared to leaching in bare soil. The half-life of ethofumesate in bare soil was 51 days compared to 3 days in turfgrass. Halofenozide showed similar leaching with or without turfgrass. Fifty percent dissipation of halofenozide did not occur within 64 days, regardless of organic matter cover.