The role of imported produce in the spread of invasive pests

Originating from East Asia, the box tree moth was first discovered in Kent in 2007 on imported box trees and has since spread throughout Britain. Identified by its white delta-shaped wings with iridescent brown borders, box tree moths only lay their eggs on box (Buxus) plants, from which their green, black, and yellow striped larvae hatch.  

Spinning a dense mat of webbing amongst the plant, the larvae then feed on the leaves defoliating and often killing smaller plants and bushes. Since first invading, it’s become clear that the box tree moth copes well with Britain’s climate and once a box tree has become infested, the larvae are effectively protected from predation and contact pesticides by the tough webbing they spin.

Whilst there’s some evidence that natural plant oils can deter adult moths from laying eggs, and that certain bacteria will kill their caterpillars, very little can be done to effectively eradicate an infestation once it’s become established and protected within webbing.  

However, it’s very likely that in the near future, the box tree moth will be finding it increasingly harder to survive in Britain, since many of the plants, bushes, and hedges that it infects appear not to recover from the feeding damage and die. Consequently, gardeners are now replacing Buxus with alternative species for their hedges and topiary which are not host plants for the box tree caterpillars. Alternatives such as Taxus and Lonicera nitida will make it much harder for the box tree moths to find hosts for their eggs and larvae in the future.