Are aphidophagous syrphids entering southern Ontario greenhouses?

Greenhouse vegetable and flower production is extensive in southwestern Ontario, both of which utilize biological control in integrated pest management (IPM) programs. Additionally, greenhouse tomato and many pepper producers utilize Bombus sp. for pollination. Though greenhouse structures are mostly enclosed, during warmer weather open vents allow for visitation from external pests and beneficial insects. Syrphid adults feed exclusively on nectar, honeydew and pollen, while predacious larvae primarily eat aphids. In this study, weekly observations were made in southern Ontario greenhouses to confirm presence of aphidophagous syrphids and identify potential for its use in biological control. Greenhouse tomato, pepper, cucumber and chrysanthemums were sampled for presence of pests and exogenous pollinators. Among vegetable crops, syrphids were observed mainly in peppers; however, higher volumes of pollinator visitations were observed in chrysanthemum greenhouses. Pepper crops also had the highest density of aphids, though no correlation with syrphid density was observed. Syrphid larvae were observed in aphid colonies at one pepper location. Further research is required to determine the syrphid species best suited for IPM in southwestern Ontario greenhouse production.