Waxy bloom in peas influences the performance and behavior ofAphidius ervi, a parasitoid of the pea aphid

Abstract

AbstractLeaf surface waxy bloom can influence the predator–prey interactions that take place on peas. We tested whether the interaction between the pea aphidAcyrthosiphon pisumHarris (Homoptera: Aphidae) and a parasitoid,Aphidius erviHaliday (Hymenoptera: Aphidiidae), is affected by reduced wax. We performed greenhouse experiments comparing aphid parasitism by individualA. ervion two varieties of reduced wax peas to two normal wax sister varieties. We also observed the behavior of individualA. erviin the greenhouse and measured field parasitism in small plots of reduced wax and normal wax peas. In the greenhouse, individualA. erviparasitized more aphids on the reduced wax varieties than on their normal wax counterparts. Wasps spent more time actively foraging on reduced wax pea plants, which may contribute to the higher parasitism observed on those varieties. The greenhouse results suggested that the improved performance of individualA. ervion reduced wax peas might contribute to a higher parasitism on reduced wax peas in the field. Field parasitism was significantly higher in reduced wax pea plots during 2000. Overall parasitism was higher in 2000 than in 2001 and 2002. In the latter years, parasitism was higher on reduced wax plants, but not significantly different from normal wax plants. Improved foraging by individualA. erviresembles improved foraging by other carnivorous insects on reduced wax peas. The advantages of reduced wax for biological control of the pea aphid may hold when any of several different natural enemies is abundant.