Effect of fipronil on permethrin sensitive and permethrin resistant strains of blattella germanica

Strategies to manage resistance to insecticides have usually been designed when resistance has already been developed. However, if the likelihood of resistance development to novel insecticides can be predicted before their use, it should be possible to establish an effective resistance management program. The current study was designed to investigate the effect of fipronil against permethrin sensitive and permethrin resistant strains of Blattella germanica (L.) for effective control of this pest in Iran in the future. In order to conduct this study eleven feral German cockroach strains were collected from infested student dormitories of Tehran University of Medical Sciences, Sanatee Sharif, Tarbiat Modares and Tehran Universities and also residential Saman Apartments, and two infested hospitals in Tehran. Their sensitivity to permethrin and fipronil were compared with that of a standard susceptible strain. Tests were conducted on newly emerged adult males (ultimately 21 years old) by topical application. LD50`s of permethrin and fipronil for the susceptible strain were 0.43µg and 0.96 ng respectively. The resistance of feral strains to permethrin was 8.6 to 17.7 times as much as that of the susceptible strain. According to this investigation all strains are resistant to permethrin, whereas resistance rates of the strains from Bustan-10, Zanjan Fatemiyeh dormitories and residential Saman Apartments were 2 to 2.6 times more than that of the susceptible strain. Other strains were completely susceptible to fipronil. According to the results of this study and considering ever-increasing infestation of human habitations by German cockroach and the resistance to insecticides; fipronil especially its toxic bait formulations can be regarded as the appropriate candidate to control this pest in Iran.