The overall goal of this project is to develop a model that will account for levels of indigenous predation while exploring the parasitism required by an introduced parasitoid in order to control the mealy plum aphid, Hyalopterus pruni. Parameters for this model have been estimated from field and laboratory data. We have measured aphid and predator population densities over three years. The aphid population growth parameters were determined in prune orchards by excluding predators from small sleeve cages and in the laboratory on potted prune trees. The proportion of time predators spend feeding was measured by direct observation in prune orchards. The time individual predators take to consume a single prey item was measured in the laboratory. The mass of aphids consumed by individual predators, Chrysopa nigricornis and Harmonia axyridis, was measured over 24 hour periods in both the field and the laboratory. The functional response of Aphidius transcaspicus was determined by enclosing individual parasitoids in sleeves with different aphid densities on branches in prune orchards. We have combined estimates of predation rates of each predator species with 96-98 field data on aphid and predator densities to quantify the impact of predation on the mealy plum aphid. Thus, we have calculated the estimated predation potential of the predator guild and the required predation potential needed to account for the observed change in aphid population density for a known rate of aphid increase.
Species 1: Homoptera Aphididae Hyalopterus pruni (mealy plum aphid)
Species 2: Neuroptera Chrysopidae Chrysopa nigricornis (green lacewing)
Species 3: Hymenoptera Braconidae Aphidius transcaspicus
Keywords: predation, parasitism
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