Many US and Canadian municipalities, states, and provinces discourage the use of pesticides to varying degrees, making it difficult or impractical to control tree pests, like aphids. Augmentative biological control has proven effective in greenhouses and agricultural monocultures for managing aphids, but its usefulness in mosaiced urban/suburban environments is unclear. In cooperation with the city of Portland, Oregon, we released Aphidoletes midges on individual linden street trees to assess this ubiquitous biocontrol agent’s ability to mitigate aphid populations for the purpose of improving urban forest aesthetics and health. Results from the first year of data collection will be discussed.