Effect of temperature and the synergist piperonyl butoxide on imidaclopridtoxicity to the cat flea (Siphonaptera : Pulicidae)

The toxicity of imidacloprid to cat fleas on glass was investigated at 20, 26, 30, and 35 degrees C. Imidacloprid was most toxic to adult cat fleas at 35 degrees C and to larvae at 20 degrees C. Piperonyl butoxide (PBO), a sy nergist, increased the relative potency of imidacloprid (1:5 imidacloprid:P BO) 16-fold at 26 degrees C against adults, but had no effect at 35 degrees C. No synergism occurred in larvae at 20 degrees C, but addition of PBO (1 :5 imidacloprid:PBO) doubled toxicity at 26 degrees C. PBO (1:5 imidaclopri d:PBO)could possibly be used to synergize imidacloprid premise treatments ( 20-30 degrees C),but it is not likely to be effective in pet treatments bec ause no synergism occurred in adult fleas at 35 degrees C (average fur temp erature of tested cats and dogs).