Efficacy of Aphidoletes predator releases to mitigate aphid populations on linden street trees

Augmentative biocontrol has lacked research on ornamental plants in urban landscape environments. Aphids are a ubiquitous and annual pest of many urban tree species (including those that are bee-attractive), decreasing tree vigor through their sap-feeding behavior and creating a nuisance with their sticky honeydew. Augmentative biocontrol has proven effective in greenhouses and agricultural monocultures for managing aphids, but its usefulness in complex urban environments is unclear. This presentation will review results from two years of data collection investigating the ability of Aphidoletes aphidimyza (the aphid midge) augmentative releases to maintain low aphid population densities and honeydew volumes on single trees. In collaboration with the city of Portland, this study has been carried out on over 60 linden street trees. The midges, released early in the growing season, appear successful in (1) undergoing multiple life cycles on single linden trees where vials of pupae were hung and (2) maintaining a relatively low level of aphid densities and honeydew volume throughout the summer. Results from two years of data collection will be presented. As a potential new aphid management service for arborists, the release of this predator would be a cost-effective, environmentally friendly, and equally convenient alternative to traditional insecticides.