Persistence, Penetration, and Surface Availability of Cypermethrin and Its Major Degradation Products in Elm Bark

Abstract

The initial residues of cis-A, trans-C, cis-B, and trans-D cypermethrin in elm bark treated with a 400× aqueous dilution of Ripcord 40 EC (1.0 g of active ingredient/L) to runoff ranged from 29 to 58, from 24 to 53, from 25 to 35, and from 17 to 25 μg/g, respectively. These residues dissipated quickly with half-lives of 1.60−12.0 days for the faster dissipation phase. The dissipation of cypermethrin during the later period became much slower, with dissipation half-lives of 209−365 days. Cypermethrin residues in elm bark remained 100% effective against the native elm bark beetle for ∼60 days after application. Laboratory tests indicated that cypermethrin residues in the bark were 100% effective in preventing elm bark beetles from making overwintering tunnels for up to 627 days (fall application) and 433 days (spring application). No penetration of cypermethrin to the cambium layer or wood tissue was detected during the experimental period of 791 days. Total cypermethrin residue absorbed from treated elm bark during a 1 min contact period did not exceed the acceptable daily intake for humans. Keywords: Cypermethrin; degradation products; elm bark; elm bark beetle; residue; effectiveness; penetration; contact availability