Epicuticular wax on pea plants decreases instantaneous search rate of Hippodamia convergens larvae and reduces attachment to leaf surfaces

Abstract

AbstractCrop cultivar can affect the ability of natural enemies to control pest populations. Peas, Pisum sativum L. (Fabaceae), with a reduced epicuticular wax bloom have reduced pea aphid, Acyrthosiphon pisum (Harris) (Hemiptera: Aphididae), populations in the field than peas with a normal-wax bloom. In this paper we use the functional response to examine predation by Hippodamia convergens Guérin de Méneville (Coleoptera: Coccinellidae) larvae foraging on pea plants with a normal- and a reduced-wax bloom. We found that Hippodamia convergens shows a Type II functional response on both phenotypes of peas. Hippodamia convergens consumed significantly more pea aphids on reduced-wax plants than on normal-wax plants. The instantaneous search rate, a, was higher for predators on reduced-wax plants, but the handling time, Th, was similar for predators on both wax phenotypes. In addition, we tested the ability of H. convergens larvae to attach to the surface of normal-wax and reduced-wax pea leaves. We found that H. convergens larvae attach more strongly to reduced-wax peas than to normal-wax peas. These results suggest that predation of pea aphid by H. convergens is enhanced on reduced-wax peas due to increased ability of predators to attach to these plants, and as a result, search for and find aphids.