Low Heat Availability Could Limit the Potential Spread of the Emerald Ash Borer to Northern Europe (Prognosis Based on Growing Degree Days per Year)

Simple Summary Emerald ash borer is a devastating pest of ash trees. This beetle, native to Asia and established in North America, European Russia and Ukraine is quickly spreading and approaching the borders of the European Union. We made the first prognosis of the potential range of this pest in Europe based on heat availability. Our calculations have shown that, in most European countries, the climate is warm enough for the establishment of the emerald ash borer. However, this pest would probably not be able to establish itself in some regions of Norway, Sweden, Finland, Ireland and Great Britain, because there is not enough heat to complete development (the summer is too cold and too short). Therefore, there is a hope that European ash (Fraxinus excelsior) could escape from the emerald ash borer in some parts of the British Isles and Scandinavia. Emerald ash borer Agrilus planipennis (Coleoptera: Buprestidae) is one of 20 priority quarantine pests of the European Union. It is native to Asia and is established in the USA, Canada, European Russia, and Ukraine. We made the first prognosis of the potential range of A. planipennis in Europe based on heat availability. Mean annual growing degree days base 10 degrees C (AGDD(10)) was calculated for each grid square (0.25 degrees x 0.25 degrees latitude x longitude degrees) on the Earth's surface. Minimal AGDD(10) recorded in the grid squares currently occupied by A. planipennis was 714 degrees in Asia, 705 degrees in North America, and 711 degrees in European Russia. Agrilus planipennis has never been recorded in localities with AGDD(10) below 700 degrees. If the phenotypic plasticity would not allow this species to overcome this threshold, cold regions of Europe would probably not be invaded by A. planipennis. Thus, Fraxinus excelsior could potentially escape from A. planipennis in some regions of Norway, Sweden, Finland, Ireland, and Great Britain.