The effectiveness of biological control agents can be limited by several factors, including characteristics of the crop plant that may interfere with their foraging for prey. Identifying these factors and ways to reduce their impact on beneficial insects is an important endeavor to increase sustainability and reduce insecticide use in agriculture. This project will examine the effects of reduced waxy bloom in peas on beneficial insects. Prior NRI-funded work has shown that this occurs for certain predators. This project will examine the effects of pea wax bloom on parasitoids and on potential synergistic interactions between foliar predators and ground beetles.
Objective 1. To test the effect of the reduced waxboom mutation wsp in peas on predator effectiveness. We hypothesize that wsp will provide advantages to predators similar to that shown for the mutation wel. Objective 2. To determine the importance of ground beetles for increasing suppression of pea aphid populations by predators on wel and wsp reduced-waxbloom peas. We hypothesize that aphidophagous carabids will be synergistic with foliar predators. Objective 3. To determine the effects of wel and wsp on parasitism of A. pisum by one of its predominant parasitoids, Aphidius ervi Haliday. Objective 4. To measure effects of wel and wsp reduced wax mutations on the yield of peas.
APPROACH: Objective 1. We hypothesize that wsp will provide advantages to predators similar to wel. In the laboratory, effectiveness by H. convergens larvae and adults will be measured on isolines differing in wsp expression using cage studies and behavioral observations. A field trial will assess naturally occuring aphid and predator densities on wsp isolines for one season. Objective 2. We hypothesize that aphidophagous carabids, by consuming A. pisum dislodged from plants by foliar predators, will amplify and may be essential for substantial enhancement of predation on the reduced waxbloom isoline in each pair. This will be tested with inclusion cages in the field for two seasons. Objective 3. Based on the higher rates of parasitism in the field (see below), we hypothesize that individual female A. ervi will leave more progeny when attacking aphid infested reduced-waxbloom pea plants from either isoline pair. If the effect is due to parasitoid mobility while walking the plant surface in search of prey, we hypothesize it will be detectable in no-choice cage experiments. Objective 4. To measure effects of wel and wsp on yield. We hypothesize that yield penalties detectable between the wsp isolines will be less severe than wel because wax reduction is less severe, at least on a whole-plant basis. To test this, yields for the two sets of isolines will be comparedn the field for two seasons.