The turnip aphid, Lipaphis erysimi (Kaltenbach), is a specialist crucifer feeding herbivore. The peach-potato aphid, Myzus persicae(Sulzer), is a generalist herbivore with the ability to colonise and feed on a wide range of host plants including crucifers. Diaeretiella rapae (McIntosh) is a braconid parasitoid that specialises in the parasitism of crucifer-feeding aphids. The foraging behaviour and host preference of D. rapae for these two aphid species has been investigated and includes a series of attack-rate bioassays that were designed to assess the host preference behaviour of the parasitoid. These bioassays showed that D. rapae attack L. erysimi at a significantly greater rate than M. persicae irrespective of the host aphid species in which the parasitoid had developed. This is in contrast to many other aphid parasitoid species that preferentially attack the aphid/plant combination in which they had developed. A series of attack-rate bioassays using D. rapae that had been excised from their mummy cases prior to natural emergence and reared through to adulthood artificially were completed. These bioassays allowed the influence of cues received by the parasitoid upon emergence from, and subsequent exposure to, a mummy case to be assessed. The results showed that both mummy cases provide a host learning experience that causes D. rapae to attack L. erysimi at a significantly greater rate than M. persicae. We will discuss our findings in the context of quantitative and qualitative differences in the chemistries associated with L. erysimi/turnip and M. persicae/turnip interactions.
Species 1: Hymenoptera Braconidae Diaeretiella rapae
Species 2: Homoptera Aphididae Lipaphis erysimi (turnip aphid, mustard aphid)
Species 3: Homoptera Aphididae Myzus persicae (green peach aphid)
Keywords: parasitoid, behavior
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