Reversion of susceptibility to insecticides of male German cockroach of resistant strains during long-term cultivation under laboratory conditions

Under laboratory conditions, resistance to insecticides from various chemical classes was assessed on several strains of the German cockroach Blattella germanica obtained from populations collected at sites in Moscow, Kaluga, Sverdlovsk and Moscow regions. It has been established that when applied topically, German cockroaches of all strains are highly resistant to cypermethrin (RR = 133–>4000?), fipronil (RR = 14–61?), chlorpyrifos (RR = 15–40?), weakly tolerant to thiamethoxam and clothianidin (RR = 2–5?). After breeding in an insectarium without insecticide press for several generations, the resistance of M1 strain to cypermethrin decreased by 1.2 times, in U1, M9 and OBN strains resistance remained at the same high level, in U8 strain decreased by 20 times; the resistance to fipronil in M1, U1 and OBN strains decreased by 1.4, 1.7 and 5.0 times, respectively. The level of susceptibility to chlorpyrifos decreased by 1.2–2.2 times, depending on the strain. Tolerance of cockroaches to thiamethoxam and clothianidin remained at the same level. The mechanisms of resistance of the German cockroach to insecticides are discussed. Keywords: pyrethroids, neonicotinoids, organophosphorus compounds, phenylpyrazoles.