Efficacy of (s)-Methoprene against Cimex Lectularius (Hemiptera: Cimicidae)

Abstract:
Widespread resistance to conventional residual neurotoxic insecticides such as pyrethroids is likely to be a major factor in bed bug infestations. To identify an insecticide with an alternative mode of action that is effective against the bed bug, the juvenile hormone analogue (S)-methoprene, was evaluated. Adult and nymphal stages were exposed in the laboratory to deposits of technical (S)-methoprene at a range of doses. Results show that efficacy of the (S)-methoprene is expressed in a variety of ways including incomplete eclosion, formation of bedbugs with uneven cuticle, prolapses of the gut through the dorsal abdominal wall, and formation of supernumerary nymphs. The nymphs are most susceptible; there is least impact on adults. The overall impact of treatment is the failure of immature stages to develop to fertile adults. A dose of 30 mg/m2 has been shown to interrupt development of susceptible bed bugs in laboratory experiments. The efficacy of (S)-methoprene was assessed against both a laboratory susceptible strain and a field strain resistant to pyrethroid and carbamate insecticides. The field strain is believed to be typical of wild bed bug populations in the United Kingdom. (S)-methoprene was as effective against the resistant strain, as it was against the susceptible strain, suggesting that there is currently little or no field resistance to this compound.