Dissipation of cypermethrin and its major metabolites in litter and elm forest soil

Abstract Cypermethrin (40 EC Ripcord®, 1.0 g a.i./L aqueous dilution) was applied to the basal 1 m of elm tree trunks to runoff for control of elm bark beetles at two different application times and sites. The initial residues of cis‐A, trans‐C, cis‐B, and trans‐D cypermethrin isomers in litter were 54 to 141, 41 to 125, 47 to 88, and 32 to 62 μg/g, respectively, depending on the application time, and dissipated to below detection limits at 341 d after application. Total cypermethrin residues in soil fluctuated from below detection limits to 10 μg/g during the experimental period. Dissipation half‐lives of cis‐A, trans‐C, cis‐B, and trans‐D in soil fortified in the laboratory and held under field conditions were 409 to 453, 277 to 286, 345 to 473, and 249 to 263 d, respectively. The trans‐cypermethrin isomers dissipated more quickly in soil than the cis‐isomers, and cypermethrin at higher concentrations dissipated more slowly than at lower concentrations.