Three new species of ambrosia beetles established in Great Britain illustrate unresolved risks from imported wood

Abstract

Bark and ambrosia beetles (Scolytinae) are frequently introduced to new areas through international trade of wood and wood products. When novel host trees are encountered, they can be naive and susceptible to attack, enabling previously harmless scolytine species to become damaging, or the symbiotic fungi of ambrosia beetles to become pathogenic. Invasive Scolytinae are often only recognised after they have become harmful, so the early detection of such species is important for forest protection and management. The first nationwide survey of Scolytinae in Great Britain was conducted between 2013 and 2017, to determine the presence and distribution of previously undetected alien species. Study sites included pine, spruce and oak forests and forests near ports where wood and forest products are imported. Insect traps baited with ‘broad-spectrum’ lures were employed to maximise the diversity of scolytine species collected. Three recently established alien species were detected, Xylosandrus germanus, Gnathotrichus materiarius and Cyclorhipidion bodoanum; the latter two species are new records for Britain. All three species appear to be largely restricted to south-east England at present, and strikingly, all are ambrosia beetles. Current EU plant health regulations for wood importation and movement are limited in their effectiveness against ambrosia beetles, since bark removal does not typically destroy them. In the relatively cool summer climate of Britain, southern England appears to provide the most optimal thermal conditions for the establishment of invasive wood and bark-boring beetle species.