Comparative Toxicities of Some Insecticides to the Apple Maggot

LD50 levels in ng/fly were established for dimethoate, azinphosmethyl, phosmet, and phosalone by topical application of insecticides to the dorsum of the thorax of laboratory-reared adult Rhagoletis pomonella (Walsh). The LD60 for females treated with dimethoate was 2.4 ng, 11.2 ng for phosmet, 12.1 ng for azinphosmethyl, and 25.9 ng for phosalone. Males were more susceptible than females. Twenty other candidate pesticides were tested but none was as toxic as dimethoate. Eleven were about as toxic as azinphosmethyl. Diazinon and methyl parathion were the most toxic of these. Field collected flies and strains from Vermont and Quebec were not significantly different in susceptibility than laboratory reared flies. On a dry weight basis, the blueberry maggot R. mendax Curran and the apple maggot were almost identically susceptible to dimethoate.