Longevity and efficacy of pyrethroid and organophosphate termiticides in field degradation studies using miniature slabs

Abstract

Organophosphate (chlorpyrifos, fenitrothion, and isofenphos) and pyrethroid (bifenthrin, cypermethrin, lamda-cyhalothrin, and permethrin) formulations were applied in sand and covered by miniature slabs in a field study in southern Florida. Sub-slab sands were sampled annually for up to 5 yr to evaluate their barrier efficacy against the Formosan subterranean termite, Coptotermes formosanus Shiraki, and the eastern subterranean termite, Reticulitermes flavipes (Kollar). The bioassay results showed that at the rates tested under these miniature slabs, pyrethroids generally provided longer protection than organophosphates, but microencapsulated formulations extended longevity of some organophosphates. According to the half-life regression model, permethrin had the longest half-life (21.9 mo) among the 7 insecticides selected for residue analysis. Because the foundation size of a typical house is much larger than the miniature plots used in this study, our results should be interpreted with caution.