Aphidius granarius, Marsh., in Relation to its Control ofMyzus kaltenbachi, Schout

Abstract

1.Aphidius granariusis an internal parasite ofMyzus kaltenbachi, where the latter is found infesting corn crops in South Wales.2. The emergence of the adult parasite is described. Mating takes place within two hours of emergence, the females may be mated with more than one male.3. A brief description of the morphology of the egg, larval, prepupal and pupal stages is given.4. The rate of reproduction of the females ofA. granariusis high, with female: male as 12·9: 10. Unmated females always produce males.5. The adult parasite under normal conditions lives for 21–27 days and flies readily under favourable meteorological conditions. Within limited areas dissemination may be brought about most effectively by mature parasitised apterae.6. The factors limiting the effectiveness of the parasite are briefly described. The degree of control at the end of May in the field may approximate to 90 per cent.