Clonal differences in the potato aphid (Macrosiphum euphorbiae) determine responses to an aphid parasitoid

Abstract: The potato aphid (Macrosiphum euphorbiae) is an economically important pest of
strawberry crops. There is increased reliance on aphid parasitioids and predators to control this species due to withdrawal of some insecticides and indirect insecticide effects on pollinators and other beneficial insects in these crops. However, the recent description of innate resistance to a parasitic wasp (Aphidius ervi) in some populations of M. euphorbiae feeding on potato could indicate reduced effectiveness of biological control of aphids in strawberry crops where parasitoids are used. As it is not yet known if the parasitoid-resistant genotypes of M. euphorbiae also infest strawberry crops, experiments have been completed to characterize different clones of M. euphorbiae collected from strawberry crops. This study uses aphids sampled from different geographical locations in the UK, microsatellite information to genotype these aphid populations, and diagnostic PCRs to identify the presence of ‘protective’ facultative endosymbionts. In addition, behavioural responses of the parasitoid A. ervi to M. euphorbiae are characterized using laboratory bioassays to understand the role of aphid clonal variation in aphid-parasitoid interactions. Finally, the susceptibility of these aphid clonal lines to parasitism by A. ervi is recorded. Together these results provide information on the likely effectiveness of biological control programmes based on releases of A. ervi for control of M. euphorbiae in strawberry crops.