EVALUATION OF PERMETHRIN-IMPREGNATED COTTON BALLS AS POTENTIAL NESTING MATERIAL TO CONTROL ECTOPARASITES OF WOODRATS IN CALIFORNIA

The dusky-footed woodrat, Neotoma fuscipcs Baird, is a natural reservo ir of the Lyme disease spirochete, Borrelia burgdorferi Johnson, Schmi d, Hyde, Steigenwalt & Brenner, in California. To investigate the pote ntial of host-targeted insecticide to control the tick vectors of B. b urgdorferi, permethrin-impregnated or untreated cotton balls were dist ributed in metal cylinders as potential nesting material adjacent to 9 5 woodrat houses in chaparral-covered rangeland. Laboratory experiment s demonstrated that adult woodrats would enter tile cylinders and cons truct nests from permethrin-treated or untreated cotton. The residual concentration of permethrin did not vary significantly during an Ii-mo period and remained >60% of the registered insecticidal formulation ( 7.5% [AI] by cotton weight). The abundance of 4 species of ticks (Ixod es neotomae Cooley; the western blacklegged tick, I. pacificus Cooley & Kohls; I. woodi Bishopp; and the Pacific Coast tick, Dermacentor occ identalis Marx) infesting woodrats was similar in the treatment and co ntrol areas. Although >90% of the cotton disappeared from the metal cy linders in both areas, examination of 8 active woodrat houses revealed that small amounts of cotton had been incorporated into tire nest cup s of only 25%. In contrast, the abundance of the flea Orchopeas sexden tatus (Baker) decreased significantly in the treatment area only Spiro chetes were not detected in 168 adult O. sexdentatus fleas that had fe d on spirochetemic woodrats, which demonstrates that this flea is an i nefficient host of B. burgdorferi. We conclude that the use of permeth rin-impregnated cotton as potential nesting material is ineffective fo r controlling ticks associated with the dusky-footed woodrat in brushl ands, but this methodology may be useful for I educing populations of sylvatic fleas.