The incidence of oak processionary moth (OPM), Thaumetopoea processionea L. (Lep., Notodontidae), in Central Europe has increased since the 1990s. Given potential climatic and land-use changes, increased abundance and range expansion of OPM may occur in the future. These changes could lead to more severe defoliation of oaks and higher threats to humans and animals, caused by the urticating hairs (setae) released by OPM larvae. These negative impacts on oak trees, people and animals urgently require effective hazard mitigation strategies.

For OPM hazard assessment and decision support on OPM monitoring and control, the online early warning system “PHENTHAUproc – phenology modelling of Thaumetopoea processionea” was created and validated. PHENTHAUproc implements daily updated temperature-based procedures to calculate the phenological development of OPM and to model the host trees’ phenology, i.e. bud swelling and leaf unfolding of Quercus robur L.

The hatching date of the first instar larvae (L1) is calculated using three different already existing models. To determine the onset of L1 feeding, a bud swelling model for Q. robur was generated for the first time. The phenological development of OPM larvae and pupae is predicted by a model which was first created based on laboratory rearing data for the distinct development stages.

Moreover, an existing leaf unfolding model for Q. robur was included into PHENTHAUproc. The predicted date of leaf unfolding can be complemented by in situ observations of leaf unfolding by the German Meteorological Service (DWD). The predicted dates of leaf unfolding and OPM forth instar development are used to define the optimal timespan for control measures such as the prophylactic spraying of biological insecticides. In addition, modelling of larval and pupal development can be used to estimate the seasonally increasing hazard resulting from setae dissemination, as well as to calculate the onset of monitoring of flying moths with pheromone traps.

PHENTHAUproc provides phenological forecasts on a local and regional level, i.e. for weather station locations and raster maps countrywide. The models can be used anywhere in Europe as soon as air temperature data and information on potential adaptations of OPM to local climate and host tree phenology are available. This enables phenological forecasts for timely and effective protection of oak tree vitality as well as human and animal health against OPM-related hazards.