Long-term trends in apple pest phenology and population variability across the eastern United States

Climate change differentially impacts the phenology of insect species based on a range of factors related to local climate and life history traits. Trap catch data collected primarily for the purpose of making short-term management decisions is often underutilized for understanding these shifts. I analyzed trap catch data from New York (1999–2020) to evaluate shifts in phenology for two major apple pests: Rhagoletis pomonella (apple maggot) and Grapholita molesta (oriental fruit moth). Linear models of annual emergence dates and thermal requirements over time revealed a significant phenological delay for R. pomonella, in contrast with earlier emergence of G. molesta. Phenology varied more over time than space, and chill accumulation during the previous winter was an important driver of emergence timing for both pests. Differences in the directionality of phenological shift may be linked to important life history traits (e.g., diet breadth, voltinism, or overwintering microhabitat). This research demonstrates the ecological value of historical monitoring data for understanding shifts in pest phenology and improving long-term management strategies.