Temporal dynamics of woodpecker predation on emerald ash borer (Agrilus planipennis) in the northeastern USA

1 Woodpeckers (Picidae) are important natural enemies attacking emerald ash borer (EAB) Agrilus planipennis Fairmaire in North America. There can be considerable variation in predation levels within and between sites, and among different times of year; therefore, understanding what causes these differences is necessary for effectively predicting EAB population dynamics. 2 We examined the temporal dynamics of woodpecker predation on EAB in Michigan and Maryland, as well as how they were affected by season, region, resource availability, tree size and crown condition. In Michigan, we quantified predation in association with EAB developmental stages on different trees over 2 years, whereas, in Maryland, we recorded woodpecker attacks on the same trees for 1 year. 3 Season was a significant predictor of woodpecker predation, with most occurring in winter when late-instar larvae were abundant. Predation also was affected by crown condition and tree size. Additionally, predation levels were similar throughout the year in a region where generations are considered to be less synchronized, representing a more consistent resource for woodpeckers. 4 The present study highlights the various factors affecting woodpecker predation over time. The results demonstrate the importance of multi-season studies of interactions between invasive species and native natural enemies when aiming to fully understand their dynamics.