The use of Warfarin is controlled by the Grey Squirrel (Warfarin) Order 1973, which permits the poisoning of grey squirrels for the purpose of tree protection. Grey squirrel bark stripping damage is seasonal, occurring from late April until the end of July. Squirrels will re-colonise woodlands from which they have been cleared within one to three months and therefore removing squirrels at any time of the year, other than just prior to and during the damage period, will have little effect on tree damage prevention. In accordance with the Control of Pesticides Regulations 1986, the product label specifies that Warfarin may be deployed to control grey squirrels between 15 March and 15 August.
Warfarin may only be used to control grey squirrels for tree damage prevention, and only ‘grey squirrel bait’ is approved for use against grey squirrels. Under the Wildlife and Countryside Act 1981 Warfarin cannot be used where red squirrels or pine martens are present.
No consideration has been given to extending the period in which Warfarin can be used. The Increased use of Warfarin would go against the stringent requirement in the UK Woodland Assurance Standard for pesticides reduction.