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

A high trichlorfon resistance was found for several housefly populations in Finland (FEAKINS and TIPTON, 1971), Belgium (KEIDING, 1978) and in the Federal Republic of Germany (KÜNAST and MESSNER, 1979; KEIDING, 1980). In England, two surveys showed high trichlorfon resistance (CHAPMAN and LLOYD, 1981; CHAPMAN, 1984) and no population with normal sensitivity was found. Trichlorfon resistance also exists outside Europe, in Southeast Asia and Africa, although in a lower degree (KEIDING, 1971). Moderate resistance to dichlorvos, used first as a bait (BAILEY, BRECQUE and WHITFIELD, 1971) then as a spraying agent (GEORGHIOL

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, HAWLEY and LEE, 1976; BOXLER and CAMPBELL, 1983), developed in the United States and Canada (BATTH and STALKER, 1970). GEROLT (1974) reported dichlorvos resistance from Finland while GUILLET (1976) from France. In Czechoslovakia RUPES et al. (19 76) found a maximum 126-fold resistance, while in his survey covering several Arab countries TAYLOR (1982) observed a 100-fold or nearly 100-fold resistance in four housefly strains. CHAPMAN (1984) monitored the insecticide resistance of 14 housefly populations in England, and found only moderate dichlorvos resistance (for one English housefly population CHAPMAN (1985) measured a 22-fold resistance). In Japan most housefly strains had moderate dichlorvos resistance (YASUTOMI, 1973); however, in some cases very high values occurred. The highest fenitrothion resistance was found in Japan: in some cases thousandfold resistance values occurred (HAYASHI et al.,1973, 1977; YASUTOMI, 1978; SHONO and MASUHISA, 1983). From England CHAPMAN (1985) reported a 94-fold fenitrothion resistance for one housefly strain, in Czechoslovakia RUPES et al. (1975, 1983) and in some Arab countries TAYLOR (1982) found that part or the populations had moderate, whereas others 50- to 100fold fenitrothion resistance. According to the results of KEIDING (1976), in Denmark houseflies had only moderate resistance to fenitrothion. In Hungary, of the organophosphate insecticides SZTANKAY-GULYÁS and ERŐSS (1970) monitored the trichlorfon, malathion and diasinone resistance of a housefly population, but failed to demonstrate any resistance. SZABÔ (1974, 1974a) examined two populations for trichlorfon, dichlorvos and fenitrothion resistance, and found substantial (300-fold) resistance to trichlorfon. Resistance to the other two agents tested was at a low level. 3

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—I I I 1111 r~3 04 1 «3 100 1000 10 000 100 000 Log dosage (jug/y) Fig. 1 Dose-response regression lines for trichlorfon tested against field-collected populations and WHO/SRS reference strain of housefly