Augmentative releases of insectary-reared lacewings for aphid control in apples

In Washington State (U.S.) apple production, adoption of augmentative releases of commercially-reared lacewings for aphid management is increasing, likely due to expanding organic acreage and a lack of effective chemical options. To address the lack of research-based best practice recommendations for this crop, we compared releases of different lacewing species (Chrysoperla rufilabris, C. plorabunda, C. carnea), life stages (eggs versus larvae), and release methods (sprinkling by hand, egg cards, drone dispersal) for aphid suppression and lacewing survival. Pest and intraguild prey consumption in the field was examined with molecular gut content analysis, using both universal and species-specific primers. In 2021, one hand release of C. plorabunda eggs or C. rufilabris larvae reduced aphid populations by ∼50 % compared to the control, but a release of C. carnea larvae or C. rufilabris eggs did not. In 2022–2023, none of the release treatments decreased aphid abundance, likely because initial aphid numbers were much higher. Recovery of released lacewings was also low in 2023, potentially due to pesticide applications. The highest lacewing larvae recapture rates occurred in the egg card and hand-released larvae treatments; larvae recaptured from these treatments also more frequently tested positive for pest aphid DNA. We found no evidence that lacewing larvae consume other orchard predators. Our initial results indicate that lacewing releases may substantially reduce aphid abundance, but release efficacy is highly dependent on release method, life stage, and timing. Early season releases at the first sign of aphids appear to be particularly critical for success.