The grey squirrel (Sciurus carolinensis) was introduced from North America in the nineteenth century. It is widely established and many people value its presence in urban parks and gardens. However, grey squirrels have displaced our native red squirrel (Sciurus vulgaris) throughout much of England, Wales and central Scotland and threaten its continued survival. In addition, grey squirrels strip the bark from trees, particularly broadleaved species, which can lead to degrade and tree death. Damage occurs when squirrel densities are high (5 per ha) and when there are large numbers of juveniles entering the summer population.
While it is neither practical nor desirable to completely eradicate grey squirrels, targeted control to protect valuable and vulnerable trees is often necessary. A method to improve targeting of control to prevent/ reduce bark-stripping damage whilst minimising the number of squirrels culled and associated costs is under investigation.
Efficacy of control should be judged upon whether there is unacceptable damage or not related to the level of control effort applied for the current years squirrel population. For example a population reduction of 2 per ha from 6 to 4 per ha should be effective at minimising damage as the population is reduced below 5 per ha. The same effort reducing a population by 2 per ha from 12 to 10 squirrels per ha will be ineffective in terms of damage control, as the population density remains well above 5 per ha.
Note - using warfarin: Following the review by the European Commission, continued use of warfarin for controlling grey squirrels after April 2007 is on condition that only pre-prepared products or baits are marketed rather than concentrates.
Publications
Controlling Grey Squirrel Damage to Woodlands (PDF-1779K)
Forestry Commission Practice Note 4 provides full details of grey squirrel management to control damage to trees.
Reducing pesticide use in forestry
Forestry Commission Practice Guide 15 provides guidance on how to reduce pesticide impacts in all forms of woodland pest and disease management.
Manufacturer and supplier information
Manufacturers and suppliers of equipment for grey squirrel control
Manufacturer's information on the current Chemicals Regulation Directorate (CRD) approved concentrate.
