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 ap plication protocol before construction. Termiticides (active ingredien t) tested were: Dursban TC (chlorpyrifos), XRM-5160 (chlorpyrifos), Eq uity (chlorpyrifos), Dragnet FT (permethrin), Prevail FT (cypermethrin ), Biflex FT (bifenthrin), Pryfon 6 (isofenphos), Demon TC (cypermethr in), PP321 (lambda-cyhalothrin), and Sumithion 20MC (fenitrothion). Be cause the vertical integrity of the treated sand was maintained, termi tes were exposed to termiticides in the same orientation as would occu r under field conditions. Results 3 h after the termiticide applicatio n indicated that all formulations of termiticides tested provide equal barrier protection against the eastern subterranean termite, Reticuli termes flavipes (Kollar). The Formosan subterranean termite, Coptoterm es formosanus Shiraki, however, generally tunneled deeper into sand tr eated with organophosphates than sand treated with pyrethroid termitic ides. Treated plots were covered by concrete slabs for 1 yr. Results o f a second bioassay with the 1-yr-old samples indicated the, loss of b arrier efficacy of the isofenphos treatment against both termite speci es. Possible factors that contributed to isofenphos degradation are al kaline sand, high precipitation, and microbes.