[Comparison of PBO and DEF effects on creating bendiocarb and carbaryl insecticide resistance in German cockroach]

ABSTRACT

German cockroach [Blattella germanica, BlattodeaBlattellidae] is considered one of the common pests in hospitals, hotels, households and dormitories which can transfer different pathogenic fungi, viruses and bacteria. The aim of this study was to determine the resistance mechanisms to bendiocarb and carbaryl in German cockroache, in vivo. In this study, German cockroach strains were collected from several hospitals and dormitories in Tehran and transferred to insectarium. The strains were reared under the same laboratory conditions. At first the discriminative doses of bendiocarb and carbaryl were determined by surface contact method. Then the susceptibility level and types of resistance mechanisms to bendiocarb and carbaryl, in the strains were studied by using PBO and DEF as synergists. Simultaneous use of DEF as synergist, with bendiocarb and carbaryl led to the breakdown of resistance in all strains. But use of PBO instead of DEF did not overcome the resistance in the strains collected from Mofid, Alvand and Vali Asr hospitals and Shariati dormitory. In general, the effect of DEF in breaking the resistance was more than that of PBO. Complete breakdown of resistance after simultaneous use of DEF with bendiocarb and carbaryl insecticides, indicated the essential role of esterase enzymes in producing resistance to bendiocarb and carbaryl in the strains. But PBO did not break the resistance completely in most wild strains, which may be due to other possible mechanisms of resistance such as reduction of cuticle penetration or insensitivity to acetyl cholinesterase enzyme