D3084: Host-stage preference of the hyperparasitoid Alloxysta brevis and potential effects of hyperparasitism on soybean aphid biological control by the parasitoid Aphelinus certus

Aphelinus certus Yasnosh is an introduced primary parasitoid of the soybean aphid (Aphis glycines Matsumura) – an invasive, economically important pest on soybean in North America. Though A. certus has displayed the capacity to suppress aphid infestations below pesticide spray thresholds, studies have shown it to be inconsistent in the field. A. certus commonly experiences hyperparasitism, which may contribute to inconsistent biological control spatially and temporally. This lab study investigates the impact of hyperparasitism on A. certus and soybean aphid populations through two experiments. In the first experiment, we investigate the host-stage preference and development time of Alloxysta brevis Thomson, a common A. certus hyperparasitoid in North America. In a second experiment, we conduct a mesocosm study to evaluate population dynamics between soybean aphid, A. certus, and A. brevis. This experiment examines the effect of hyperparasitism by A. brevis on A. certus populations, and the resulting effect on the ability of A. certus to suppress aphid populations. We also investigate the possibility that A. brevis may impact A. certus sex ratios, which could influence the reproductive potential of A. certus populations in the field.