Trap color influences capture rates of <i>Aphelinus mali</i> , a key parasitoid of woolly apple aphid ( <i>Eriosoma lanigerum</i> ) in apple orchards

Aphelinus mali (Haldeman) (Hymenoptera: Aphelinidae) is an effective endoparasitoid of the woolly apple aphid, Eriosoma lanigerum (Hausmann) (Hemiptera: Aphididae), a globally important pest of apple orchards. Reliable monitoring of A. mali populations is essential for evaluating its establishment and effectiveness as a biological control agent within integrated pest management systems. This 3-yr field study evaluated the efficacy of yellow, blue, and white pan traps for capturing adult A. mali in 9 commercial apple orchards in Pennsylvania, representing both conventional and reduced-risk pesticide programs. Weekly sampling was conducted from April through October, and data were analyzed using a generalized linear mixed-effects model with a negative binomial distribution to account for over-dispersed count data. A total of 526 A. mali adults were captured over the study period. Trap color had a significant effect on capture rates, with yellow traps collecting over 6 times more parasitoids than either blue or white traps, which did not differ significantly. Capture rates were not significantly affected by the pesticide management program, and no interaction between trap color and management regime was detected. Analysis of seasonal dynamics revealed significant differences in monthly capture rates, with peak activity occurring during July and August for this region. These findings demonstrate that yellow pan traps provide a simple, standardized, and cost-effective tool for monitoring A. mali populations, supporting improved decision-making and reduced reliance on chemical inputs in sustainable apple orchard management.