Potential Westward Spread of Emerald Ash Borer, Agrilus planipennis Fairmaire, 1888 (Coleoptera: Buprestidae) from Eastern Ukraine

Emerald ash borer (EAB), Agrilus planipennis, is a phloem-boring beetle, native to East Asia that has become a serious invasive pest of ash (Fraxinus spp.) trees in North America and European Russia since the early 2000s. In 2019, EAB was detected in Ukraine. It had spread over 300 km from the entry point over two years and killed hundreds of Fraxinus excelsior and F. pennsylvanica trees. EAB poses a threat to the ash forests of neighboring European countries, which have already been damaged by the invasive fungus Hymenoscyphus fraxineus. The purpose of this research was (i) to reveal the traits of EAB and the climatic variables that affect its survival; (ii) to predict the EAB expansion range in Ukraine and westward; and (iii) to compare the most significant bioclimatic variables in the native, invasive ranges of EAB, as well as outside these ranges. The results demonstrated the following: (i) in all ranges, EAB has adapted to the seasonal temperature variations; (ii) the MaxEnt model predicted the potential distribution of EAB with high accuracy (AUC = 0.988); the predicted area of EAB invasion covered 87%, 48%, and 32% in Luhansk, Kharkiv, and Donetsk regions, respectively; and (iii) the ranges of climatic variables in EAB-inhabited regions demonstrated the high ecological plasticity of this pest. However, the predictions could be improved by considering forest structure, as well as the localization of roads.