Oviposition preference of the predatory midge Aphidoletes aphidomyza for the biological control of greenhouse aphid pest species

In recent years, foxglove aphid (Aulacorthum solani) (Kaltenbach) has progressed from an occasional pest to a serious pest of many world-wide crops such as potato, pepper, lettuce, and soybean. Now greenhouse floriculture growers in the Northeastern U.S. and Ontario are finding foxglove aphid to be one of their most common aphid problems, adding to the complex of greenhouse aphid pest species. Rather than rely on multiple natural enemy species to manage this pest complex, we seek a single effective natural enemy. As part of our explorations into using the predatory midge Aphidoletes aphidimyza (Rondani) (Diptera: Cecidomyiidae) for aphid control in floriculture crops, we investigated the oviposition preference of Aphidoletes on plants infested with foxglove aphid or a second major aphid pest (green peach aphid (Myzus persicae) (Sulzer)). Results indicate that Aphidoletes oviposition choice is heavily influenced by aphid density. In trials where aphid numbers were manipulated on specific leaves of whole plants, a significant positive correlation between aphid density and Aphidoletes oviposition per leaf was found (R²=0.64, p < 0.0001 for foxglove aphid; R²=0.60, p < 0.0001 for green peach aphid), while aphid species was not significant (F=1.18, p=0.278). Further testing using naturally distributed populations, however, revealed that characteristics of aphid species (e.g. preferred location on the plant) significantly impact Aphidoletes oviposition (location was significant at F=23.71, p <0.0001, as were species (F=45.37, p < 0.0001) and density (F=4.23, p=0.040)). Future work will concentrate on determining how species differences might affect the efficacy of aphid biocontrol programs using Aphidoletes.