Current Certification and Approval Status of Warfarin

Current Certification and Approval Status of Warfarin

Dr Ian Willoughby FICFor, Programme Group Manager (Regeneration and substainable silviculture) at Forest Research, has produced an independent report on the current certification and approval status of warfarin. 

Updated 2/09/14

My understanding of the current situation regarding the status of warfarin for grey squirrel control in UK forests is as follows.


Although warfarin is widely used as a medicine, and the UK registered product Grey Squirrel Bait is considered Not Hazardous if used as directed, warfarin itself is categorised as a Type 1B substance by the World Health Organisation based on its mammalian toxicity. As such, it can only be used on estates certified to PEFC standards via UKWAS if there are no effective and practicable alternatives available and if there is a mechanism for sanctioning its use by the PEFC. To fulfil this requirement, PEFC UK have approached the PEFC board asking them to consider sanctioning its continued use on PEFC certified estates in the UK. The PEFC board have agreed to this in principle, but this now needs to be approved by the PEFC Council, and this process may take 2-3 months to complete. Until then, warfarin use is permitted on estates certified to PEFC standards via UKWAS.

However, warfarin is on the Forest Stewardship Council’s (FSC) so called ‘highly hazardous’ list, which means it cannot be used on estates certified to FSC standards via UKWAS, unless the FSC issue a specific derogation. A derogation was granted in 2009, and expired on 15th June 2014. FSC initially rejected an application to renew the derogation for the use of warfarin, the main reason being given that warfarin is no longer approved as a pesticide active ingredient in Europe. However, this failed to take into account that warfarin products can still be used in the UK until 30th September 2015 (see below).

Rather than undertaking a costly formal appeal, Larissa Chambers of the Soil Association, who coordinated and submitted the derogation extension application on behalf of certified estates, wrote to the FSC on an informal basis asking them consider extending the derogation until September 2015, to tie in with the last legal use date of the UK approved warfarin plant protection product Grey Squirrel Bait. The Pesticides Committee of FSC have now agreed to this request, and have granted a temporary derogation for the use of warfarin on certain named FSC certified estates until 30th September 2015.


In common with all pesticide (plant protection product) active ingredients approved for use in member states by the European Commission (EC), warfarin is subject to a planned periodic review. Sweden was appointed as the rapporteur member state to coordinate the review and prepare the assessment report. Killgerm are the current approval holders for the UK registered product Grey Squirrel Bait, and it is therefore the responsibility of Killgerm (or another company with the necessary data) to apply for re registration of the active ingredient at European level. Killgerm concluded that the fee Sweden was proposing to charge to consider the application made continued production of warfarin for plant protection product uses not commercially viable. Because the reapplication process was not supported, the EC withdrew all approvals for the use of warfarin as an active ingredient in plant protection products in Europe on 31st March 2014. However, as per standard practice where there are no safety concerns, member states apply a use up period after the withdrawal date, so Grey Squirrel Bait is still approved for use and disposal (although not sale) in the UK until 30th September 2015.

By contrast, warfarin remains approved for use as a biocide in Europe, and several biocide products are approved for use in the UK for vermin control. It is debateable a to whether warfarin used for grey squirrel control represents a biocide or pesticide use of the active ingredient, but currently it is viewed as a pesticide (or plant protection product).

The UK Government, via Defra ministers, have been in discussion with the European Squirrel Initiative over how to maintain approvals for the use of warfarin to control grey squirrels in the UK. One suggestion that has arisen is that reregistering Grey Squirrel Bait as a biocide could be explored. Following these discussions, the UK Government has also offered to act as the rapporteur state for the re registration of warfarin as a plant protection product active ingredient in Europe, in the hope that as the required fees are likely to be lower, it may make pursuing this route a more viable commercial proposition for the Killgerm, or any other company with the necessary data. Killgerm are meeting with the Chemicals Regulation Directorate in early July to discuss likely costs and additional data requirements.

Should Killgerm consider it commercially viable to pursue an apply for reapproval of the active ingredient, and a subsequent reapproval of Grey Squirrel Bait in the UK, based on past experience the process may take 1-4 years. It may be possible for user groups to apply for an Emergency Authorisation from the Chemicals Regulation Directorate to allow continued use of Grey Squirrel Bait whilst the reapplication process is being pursued (this is the same procedure as we are following for the herbicide Asulox). If it comes to it, the Forestry Commission have offered to help in making an application for Emergency Authorisation if necessary.

If Killgerm do decide to pursue reregistration as a plant protection product, and Emergency Approval is granted in the interim, then this would provide a good basis for making a revised application to the FSC for an extension of derogation for the use of warfarin on certified estates.


  • Grey Squirrel Bait (warfarin) can continue to be used in the UK to control grey squirrels in forests until 30th September 2015.
  • The approval holders Killgerm are reconsidering whether it is commercially viable to re-register the active ingredient and product. Their position is likely to be clearer by mid-July.
  • FSC have granted a derogation for the use of warfarin on certain named FSC certified estates until 30th September 2015.
  • Warfarin can also continue to be used on estates that are not entered into certification until 30th September 2015, and currently, pending the final decision by the PEFC Council, it can also continue to be used on PEFC certified estates.
  • Depending on the decision of Killgerm to reregister warfarin or not, it may be possible to apply for temporary Emergency Authorisation to continue to use warfarin, and also to make a revised application for derogation to the FSC.

Dr Ian Willoughby, Forest Research 2/9/14

Latest news