LAUSR

Abstract Ixodids are globally distributed pests that transmit many disease agents. Increasing resistance to conventional acaricides raises the need for alternative tactics. Novaluron and pyriproxyfen are insect growth regulators (IGRs) that have variable potencies against acarines. We conducted in vitro and in vivo experiments to assess novaluron + pyriproxyfen (marketed as Tekko Pro) against four ixodid species. Laboratory assays on the brown dog tick, Rhipicephalussanguineus(Latreille) (Ixodida: Ixodidae), and the lone star tick, Amblyommaamericanum(L.) (Ixodida: Ixodidae), reduced metabolic activity in larvae and nymphs. Concentrations of novaluron + pyriproxyfen dried on filter paper impeded molting of larval R. sanguineus (less effective against nymphs). Molting A. americanum larvae were reduced by >95% using 4 and 8 µg/cm2 eliminated molting; nymphal molting was reduced but not halted even at 16 µg/cm2. On calves, novaluron + pyriproxyfen stopped larval A. americanum metabolic function 1 d post-treatment and larvae did not molt. When larvae were released 30 d after treatment, metabolic activity was reduced by 95% and molting was reduced by 94%. Southern cattle fever tick, Rhipicephalus (Boophilus) microplus (Canestrini) (Ixodida: Ixodidae), larvae released 1 d after treatment on calves were 99% prevented from reaching adulthood. The treatment did not interfere with larval development when larvae were released 52 d after treatment. The cattle fever tick, Rhipicephalus (Boophilus) annulatus (Say) (Ixodida: Ixodidae), failed to reach adulthood when larvae were released on calves a day after treatment (residual activity was not assessed for R. annulatus). These IGRs, and possibly others, offer an alternative to conventional acaricides for ixodid control on cattle.