Report 
  Title  
  Igrs For Cat Flea (Siphonaptera: Pulicidae) Control Revisited
  Key Words  
  Methoprene, chlorfluazuron, fipronil, synergism
  Author  
  Michael K. Rust and W. Lance H. Hemsarth
  Abstract  
  The intrinsic activity of combinations of methoprene and chlorfluazuron and methoprene and fipronil was determined against larval cat fleas, Ctenochephalides felis (Bouché). Methoprene synergized the activity of the IGR chlorfluazuron and the adulticide fipronil. The LC50s of chlorfluazuron, fipronil, and methoprene were 0.187 (0.136-0.236), 0.983 (0.236-1.520), and 0.39 (0.212-0.574) ppm, respectively. Combinations of chlorfluazuron 1: methoprene 1 and chlorfluazuron 5: methoprene 1 were synergistic providing LC50s of 0.028 (0.017-0.042) and 0.23 (0.112-0.337) ppm, respectively. All other combinations of these two IGRs were antagonistic. The combinations of fipronil 1: methoprene 1 and fipronil 5: methoprene 1 were synergistic providing LC50s of 0.292 (0.221-0.360) and 0.927 (0.824-1.011) ppm, respectfully. The addition of methoprene to chlorfluazuron or fipronil allows for the reduction of amounts of both compounds needed to kill fleas and in the future may also retard the development of insecticide resistance.