INSECTICIDE RESISTANCE IN BLATTELLA GERMANICA (L.) IN THE UNITED KINGDOM

Abstract:
Resistance to organochlorine, organophosphorous (OP) and carbamate insecticides in the German cockroach Blattella germanica has been documented for many years. In the past, significant bendiocarb resistance has been reported in the United Kingdom. More recently, resistance has been reported to the pyrethroids particularly in the United States of America and Denmark. Over the last few years considerable use has been made of pyrethroids for cockroach control, although little accurate information about the current resistance status to pyrethroids in UK German cockroaches has been available until now. We have investigated the resistance status of three strains of B. germanica collected from sites in London and one from the USA to a range of OP, carbamate and pyrethroid insecticides. The assessments were made by topical application of a range of doses of technical insecticide in 0.5 pl of organic solvent to 2-3 week old male German cockroaches to produce dose response data. A tarsal contact method based on the WHO cockroach resistance test, was also used to assess resistance to some of the insecticides. High levels of resistance were found to pyrethrins and cypermethrin using both test methods. Results obtained with the topically applied synergists piperonyl butoxide and S,S,Stributylphosphorotrithioate indicated the presence of a kdr-type resistance. Although the strain from the USA showed high resistance to chlorpyrifos, only low OP resistance was found in the London strains. Resistance to carbamates was also detected in the London strains. The resistance data obtained by the two methods is presented and the differences and similarities in the levels of resistance that were obtained using the two methods are discussed in relation to their value as methods for assessing resistance.