Distribution, impact and rate of spread of emerald ash borer Agrilus planipennis (Coleoptera: Buprestidae) in the Moscow region of Russia

Abstract

Surveys of ash trees along the major motorway routes leading away from the city of Moscow during July 2013 indicated that emerald ash borer (<it>Agrilus planipennis</it>) was well established up to 235 km west of the city and 220 km to the south. Over the last 4 years, the beetle has spread in these directions at an average rate of 30–41 km year−1, which cannot be explained by natural dispersal alone and implies that human-assisted transport is contributing significantly to the spread of the pest, probably via the hitchhiking of adult beetles on vehicles. The European common ash (<it>Fraxinus excelsior</it>) is uncommon in Moscow and in the boreal forests to the west and north, but those trees that are present suggest that this species is not killed as rapidly by <it>A. planipennis</it> as North American ash species and that it may need to suffer a degree of stress before it succumbs rapidly to infestation. Nevertheless, <it>A. planipennis</it> is a major threat to <it>F. excelsior</it>, and south of Moscow, where the beetle has become established in natural broadleaved woodlands in which <it>F. excelsior</it> is a major component, many of the ash trees are suffering severe dieback and mortality. The abundance and almost continuous distribution of <it>F. excelsior</it> in these woodlands means that <it>A. planipennis</it> now has the opportunity to spread unhindered on a broad front to other countries in Europe.