Our approach to management is to breed and release a host-specific predatory beetle, Rhizophagus grandis, that is found within the pest’s natural range. This strategy is known as ‘classical’ biological control.
The biological control programme has been, and continues to be highly successful because of the extraordinary ability of the predator to locate its prey even when there are only a few infested trees in the forest.
The rearing system to breed R. grandis is efficient and flexible and that each adult now costs around only £0.10 to rear for release. In addition, because R. grandis has an extremely well-developed ability to find its prey, together with a rapid reproductive rate, only small numbers of individuals are needed to control each new outbreak. Typically around 100 adults per site.
Most of the R. grandis reared each year are released into Forestry Commission forests, but surplus insects are also supplied to private land owners, usually at no cost.
In forestry, exotic bark beetles are a particular threat because they can be concealed in imported timber. The most damaging species tunnel to form galleries within the bark of living trees where their larvae feed and develop, ultimately killing the tree.
In Britain, the spruce bark beetle, Dendroctonus micans, is a well-established pest that was accidentally introduced from continental Europe in the 1970s. Spruce is our most important commercial tree species and managing this pest is a high priority.
For more information about this biological control for the management of Dendroctonus minus contact Nick Fielding.
Additional information about Dendroctonus micans can be found on Forestry Commission web pages.
Further management information is also available at can be found in Practice Note 17: Minimising the impact of the great spruce bark beetle