Dr. Murai Éva szerk.: Parasitologia Hungarica 19. (Budapest, 1986)

Parasit, hung. 19. 1986 Insecticide resistance of houseflies (Musca dornestica L.) in Hungary. III. Resistance to pyrethroid insecticides Dr. László SZABÓ Research Institute for Heavy Chemical Industries, Veszprém, Hungary "insecticide resistance of houseflies (Musca dornestica L. ) in Hungary.III. Resistance of pyrethroid insecticides" - Szabó, L. - Parasit. hung., 19: 105- 117. 1986. ABSTRACT. In the present paper the resistance of the housefly to tetramethrin, Cypermethrin, permethrin and deltamethrin is reported. Despite the fact that in Hungary synergized Pyrethrins and pyrethroids have rarely been used, some populations exhibited moderate resistance to all the agents tested. In the case of tetramethrin, the resistance index calculated from the LD50 values was higher than 100, higher than 10, between 5 and 10, between 1 and 5, and below 1 for 2, 1, 2, 7 and 3 housefly populations, respectively (a total of 15 populations were monitored). The lowest resistance was found to Cypermethrin: in two housefly populations it was more than 5-fold, in 6 populations between 1- and 5-fold, whereas 7 populations were less susceptible than the WHO/SRS strain used for comparison. Of the 17 housefly populations monitored for permethrin resistance 2, 3 and 6 had more than 10-fold, 5-10-fold and 1-5-fold resistance, respectively, whereas 6 populations proved to be more susceptible than the WHO/SRS reference strain. One, 2, 4 and 6 of the 13 housefly populations tested for deltamethrin resistance exhibited a resistance index higher than 20, between 10 and 20, between 5 and 10, and between 1 and 5, respectively. KEY WORDS. Insecticide resistance (Musca dornestica L. ), pyrethroids, tetramethrin, Cypermethrin, permethrin, deltamethrin. Although natural and synergized Pyrethrins have long been used in housefly control, in natural populations resistance to them has rarely been encountered (FINE, 1963; BROWN and PAL, 1971). Pyrethrin resistance was observed only in Scandinavia, in some Swedish (DAVIES, KEIDING and HOFSTEN, 1958) and Danish (KEIDING, 1976) housefly populations and nowhere else, not even in Californian (GEORGHIU et al. , 19 72) and Japanese (HAYASHI and HASEGAWA, 1973; YASUTOMI, 1973) populations that had developed high resistance to organophosphates. The development of photostable pyrethroids having high insecticidal activity and long persistence period was a landmark in housefly control. The compounds (permethrin, Cypermethrin, deltamethrin) developed in 1972 and in the years that followed were put on the market very rapidly (RUSCOE, 1979), and from 1976-1977 they were regularly used in housefly control as well. However, in some countries efficacy problems emerged within a rather short time. In some housefly populations of Denmark (KEIDING, 1978) and the Federal Republic of Germany (KÜNAST, 1979, 1980) a strong resistance to permethrin had developed as soon as by 1978, but a reduced efficacy was reported from Canada as well (HARRIS, TURNBULL and WHISTLECRAFT, 1982; MacDONALD et al. , 1983). In a survey conducted in England, CHAPMAN and LLOYD (1981) found a widespread and high