Does the prediction of the time of egg hatch of Thaumetopoea processionea (Lepidoptera: Notodontidae) using a frost day/temperature sum model provide evidence of an increasing temporal mismatch between the time of egg hatch and that of budburst of Quercus robur due to recent global warming?

Thaumetopoea processionea is a serious defoliator of oak and of medical concern whose abundance has consistently increased throughout Europe during the past two decades. This study validates a previously published frost day/temperature sum model for predicting time of egg hatch of this species using five years of recent field data from South-West Germany. This model proved satisfactory for predicting the time of egg hatch of T. processionea. Hence, the model was used to retrospectively predict the time of egg hatch of T. processionea in the Karlsruhe area, which indicates that the time of egg hatch has fluctuated over the past 130 years. In the last two decades, however, predicted time of egg hatch is much earlier than the long-term average due to the increase in winter and early spring temperatures. Comparison of predicted time of egg hatch of T. processionea and long-term records of the time of foliation of its common host Quercus robur revealed that in the study area the temporal advance in the timing of both events was similar. This is not in accordance with recently published research on spring-feeding folivores, which report a diverging trend in the timing of egg hatch and budburst of their host plants as a consequence of human-induced climate change.