Final Report and Policy Document

Preliminary investigation into the threat of Bronze Birch Borer (BBB - Agrilus anxius) to Scotland

Adult Agrilus anxius, Whitney Cranshaw, Colorado State University,

The Bronze Birch Borer (BBB, Agrilus anxius) is a major threat to birch trees. This project had co-funding from Scottish Forestry and NatureScot and undertook evidence gathering to assess the threat BBB poses to Scotland, inform risk assessment, surveillance and contingency planning, and identify key risks and knowledge gaps.

The team discovered there had only been 10 recordings of Agrilus species in the UK.   Sticky prism traps and multi-funnel traps deployed in Scotland caught no Agrilus species. In parallel Euphresco trials (England, Europe and north America), Agrilus beetles were caught in both trap types, although Agrilus anxius beetles were only detected in North America. No trap performed better than the other and results indicate that factors such as position and climatic conditions influence the abundance of Agrilus captured. Recommendations from the project include (i) investigating and/or developing alternative trapping methods, especially with morphological and behavioural traits of the target species in mind, to reduce the capture of non-target species; (ii) development of an improved birch tree species distribution model to include impacts of land management and land use change as well as coexistence of birch species with other tree species; (iii) investigations are required into the plausibility of small shipment pathways for entry of BBB; and (iv) development of realistic policy and economic scenarios for use in trade modelling to reveal potential tipping points for large scale changes in processed or unprocessed birch into the UK.

Image credit: Adult Agrilus anxius, Whitney Cranshaw, Colorado State University,