Evaluating Syrphid Fly Predation on Aphids Under Controlled and Field Conditions in High Tunnels: A Comparative Study With Lacewings

Abstract

Biological control in high tunnel systems can be optimised by matching predator species to seasonal environmental conditions. We evaluated the predatory efficacy of syrphid flies (Toxomerus marginatus (Say), Eupeodes americanus (Fabricius)) and lacewings (Chrysoperla carnea (Stephens), Chrysoperla rufilabris (Burmeister)) across laboratory bioassays and seasonal high tunnel field trials in 2024–2025. Syrphids and lacewings performed similarly at 23°C, but lacewings showed higher feeding than syrphids at 30°C/25°C (day/night), indicating that lacewings are more effective under the warmest conditions while syrphids remain consistent across moderate and warm temperatures. Spring high tunnel observations showed that peaks in syrphid egg and larval abundance consistently preceded declines in aphid populations by 1–2 weeks, indicating a top-down regulatory effect. These findings underscore the value of syrphids as biological control agents in spring and fall crops, while lacewings may be better suited for summer releases under higher temperatures.