Effect of parasitism by Aphelinus spiraecolae (Hymenoptera: Aphelinidae) on development and reproduction of spirea aphid (Homoptera: Aphididae)

The effect of parasitism by Aphelinus spiraecolae Evans and Schauff on development, survival, reproduction, and population growth of different life stages of the spirea aphid, Aphis spiraecola Patch, was assessed in the laboratory. Differences in aphid population growth were related to the life stage attacked. Aphids parasitized as 1st and 2nd instars and 40% of those parasitized as 3rd instars died as 4th instars. Approximately 60% of aphids parasitized as 3rd instars and all parasitized as 4th instars and adults reached maturity and produced a variable number of offspring, with those stung as adults producing more. Parasitized adult aphids stopped producing offspring approximately 6 d after parasitoid attack. Parasitism by A. spiraecolae decreased life span, fecundity, and intrinsic rate of increase of the spirea aphid and increased aphid doubling time at rates dependent on the host stage parasitized. These data indicate that this parasitoid has potential as as a natural enemy of the aphid and should be further evaluated