Barrier Efficacy of Pyrethroid and Organophosphate Formulations Against Subterranean Termites (Isoptera: Rhinotermitidae)

In a laboratory bioassay, termites were allowed to tunnel into a 5-cm core sample of sand (pH 8.1) treated with termiticides following an application protocol before construction. Termiticides (active ingredient) tested were; Dursban TC (chlorpyrifos), XRM-5160 (chlorpyrifos), Equity (chlorpyrifos), Dragnet FT (permethrin), Prevail FT (cypermethrin), Biflex FT (bifenthrin), Pryfon 6 (isofenphos), Demon TC (cypermethrin), PP321 (lambda-cyhalothrin), and Sumithion 20MC (fenitrothion). Because the vertical integrity of the treated sand was maintained, termites were exposed to termiticides in the same orientation as would occur under field conditions. Results 3 h after the termiticide application indicated that all formulations of termiticides tested provide equal barrier protection against the eastern subterranean termite, Reticulitermes flavipes (Kollar). The Formosan subterranean termite, Coptotermes formosanus Shiraki, however, generally tunneled deeper into sand treated with organophosphates than sand treated with pyrethroid termiticides. Treated plots were covered by concrete slabs for 1 yr. Results of a second bioassay with the 1-yr-old samples indicated the loss of barrier efficacy of the isofenphos treatment against both termite species. Possible factors that contributed to isofenphos degradation are alkaline sand, high precipitation, and microbes.