Winter moth, Operophtera brumata, population dynamics I: Modeling egg hatch

Winter moth, Operophtera brumata (Lepidoptera: Geometridae), invaded the northeastern U.S. from Europe in the late 1990s resulting in widespread defoliation of deciduous trees and blueberry crops from southeastern Connecticut to coastal Maine. While biocontrol of winter moth through the introduction of Cyzenis albicans (Diptera: Tachinidae) has been largely successful in eastern Massachusetts and Rhode Island, annual outbreaks of winter moth still occur in parts of coastal Maine. Furthermore, winter moth is likely to remain a pest of apple orchards, as it did in Nova Scotia following successful biological control in the 1960s. Egg hatch generally coincides with bud break of host species, as first instar larvae bore into and feed on expanding buds. Therefore, predicting the timing of winter moth hatch has implications for understanding population dynamics of winter moth in its invasive range, as well as applications for successful control of populations in orchard settings. Using data from a series of lab and field experiments we developed an exponential growth model with an age-dependent response to temperature that predicts timing of egg hatch with temperature data from nearby weather stations. We discuss results in the context of phenological models of this system and their implications for predicting and managing population dynamics of winter moth in the northeastern U.S.