RRAG Aims and Objectives

To provide information on rodenticide resistance avoidance and management strategies for use by professional pest control practitioners, regulatory authorities, local authorities and UK farmers and growers by:

  • Acting as a central forum for exchange, interpretation and dissemination of accurate information on the extent and consequences of rodenticide resistance in the UK
  • Identifying research needs and to communicate them to appropriate agencies
  • Establishing methods of minimising the adverse effects of rodenticide resistance, including potential effects on health, food safety, environment, wildlife and economics
  • Publishing guidelines for farmers and pest control technicians and producing agreed statements to the media
  • Liaising with appropriate individuals and organisations in the UK and elsewhere, including the international Rodenticide Resistance Action Committee (RRAC).


Publication Author File Version/ Date Size Document
UPDATED Anticoagulant resistance in the Norway rat and guidelines for the management of resistant rat infestations in the UK RRAG .pdf Version 3: 2021 2.76 MB Download
UPDATED House Mouse Resistance Guidelines RRAG .pdf Version 3: 2021 3.77 MB Download
Rodenticide Resistance Strategy RRAC .pdf Version 1: 2015 7.5 MB Download

Your rat tails needed now for resistance testing

A resistance mapping survey is underway which aims to provide preliminary data on the distribution of anticoagulant resistance in the Norway rat. This survey is funded entirely by the pest control industry (BASF, Bayer, Bell, Killgerm, PelGar, Syngenta and also BPCA and NPTA) but is managed by an independent scientific
committee to ensure that the results are seen to be both rigorous and independent.

Between 600 to 1,000 tail tips are required from seven areas across mainland Britain. The focus of the research is on a series of hot spots where it is known, or suspected, that the resistant rats predominate. To establish the extent of the anticoagulant resistance on behalf of the pest control industry, the organisers require your help, now.

Shown below are the seven areas where the tips of rat's tails are sought. The study is using spatial mapping by sampling along transects that cross-resistance foci.

How you do it

Tail tips (3 - 5 cm) must not be from poisoned rats – they need to be collected from rats killed by trapping, shooting or dogs. Tails can be stored in a freezer until dispatched in the supplied vial containing a preservative (one tail tip per vial). With each vial, certain data is required: the name of the collector, the date and place collected (a post code or GPS/Ordnance Survey map co-ordinate).


Need to get in touch with RRAG. Contact the BPCA technical team with RRAG in the subject and we'll make sure your message gets to the right place.


RRAG archived updates:

Sustainable Use of Rodenticides

The European Chemical Industry Council, Cefic for short, has published a document describing the way towards sustainable use of rodenticides in the European Union.

The document explains why we need rodenticides, who needs to use them and how they are used. Cefic acknowledges that anticoagulant resistance is a major obstacle to sustainable use and proposes systems of resistance monitoring and the adoption of resistance management guidelines such as those presently operating in the UK. Other recommendations include systematic monitoring of residues of anticoagulants in wildlife species, training and certification of professional pest controllers, training for other users such as farmers and gamekeepers, more point of sale information for amateurs, new comprehensive Best Practice guidelines and an extension to other EU Member States of schemes such as the UK's Campaign for Responsible Rodenticide Use (CRRU).

New Initiative in Anticoagulant Resistance by the European Commission

Prompted by a request from The Netherlands, the European Commission has asked all European Union Member States to provide an update on rodenticide resistance to the Commission's Technical Committee on Biocides. The response to the Commission for the United Kingdom will come from the Health and Safety Executive, which is the UK's Competent Authority for Biocides. HSE requested a report on the current status of anticoagulant resistance from the Rodenticide Resistance Action Group to form a part of the HSE response.

We are now almost completely reliant on anticoagulants for chemical rodent control in the EU and the incidence of resistance among both Norway rats and house mice is increasing in several Member States. It is to be hoped that this new initiative by the Commission will raise the profile of anticoagulant resistance and foster the implementation of practical resistance management strategies.

Anticoagulant Resistance among Norway rats in Holland

The results of a new DNA anticoagulant resistance survey have been published by Dutch researchers see here. The results show that 56% of Norway rats in Holland carry anticoagulant resistance mutations and 39% of rats carry mutations that are known to affect the efficacy of anticoagulants. The two mutations found most commonly, Y139C and Y139F, are both also found in the UK.

These findings have caused some concern in the Dutch biocides Competent Authority and have resulted in questions to the Biocides Technical Meeting of the European Commission at its next meeting in Italy on 21st March 2012.

An intention is to develop an inventory of resistance in the European Union and the Dutch have therefore posed the following questions to all Member States:

Questionnaire for inventory of rodenticide resistance in mice and rats

What is the current situation in your country concerning the presence of rodenticide resistance in mice and rats?

Examples: Have studies or surveys concerning rodenticide resistance been done in your country? Did these studies reveal reduced susceptibility to certain active substances or mutations in mice and/or rats in certain areas of the country?

What is the current common practice during the authorization process concerning use restrictions and resistance management strategies?

Examples: Are in some cases uses excluded, as for example private use for rat control? Is specific information added to the label concerning resistance management strategies?

Do you have any suggestions on how the problem of possible resistance development should be addressed during the product authorization process?

The RRAG hopes to work with the UK biocides Competent Authority, the Health and Safety Executive, towards answers to these important questions. 

European Commission Plans to Restrict the Use of Anticoagulant rodenticides

A document is under consideration by the European Commission and the EU Member States to decide what restrictions to put on the use of anticoagulant rodenticides. In particular, the document addresses the important resistance-breaking second-generation anticoagulants (SGARs).

Four different proposals are under consideration:

  • Proposal 1 - Restrict use of all SGARs to indoors only
  • Proposal 2 - Restrict use of all SGARs to in and around buildings
  • Proposal 3 - Maintain the status quo of certain Member States
  • Proposal 4 – Professional Use Only

Products containing difethialone, brodifacoum and flocoumafen should be authorised for indoor use only by professional users in all member states.

Products containing bromadiolone and difenacoum should be authorised for indoor and outdoor use only by professional users in all member states.

RRAG is very concerned that, in putting up these proposals, the European Commission has not properly considered their impacts on our ability to control anticoagulant-resistant Norway rats. Therefore, RRAG has written to the European Commission to express these concerns. A copy of the RRAG letter can be found here. The proposals will be considered at the forthcoming meeting of the Commission’s Product Authorisation and Mutual Recognition Facilitation Group on 28-28 February 2012.

It is an interesting contradiction that at one meeting Member States will consider the growing problem of anticoagulant resistance in Norway rats (see above) while, at another, officials will consider proposals which would virtually remove our ability to control the spread of resistant rats in the EU using the most effective resistance-breaking rodenticides.

Investigation of the current status of anticoagulant resistance in UK-Norway rats by VKORC1 genotyping

A paper was given at the 8th European Vertebrate Pest Management Conference in Berlin in September 2011 by RRAG members Drs Dougie Clarke (University of Huddersfield) and Colin Prescott (University of Reading). Information on the resistance status of more than 150 wild rats from all over the UK, obtained by DNA sequencing was presented. The abstract of the paper can be found here.

Norway rat resistance survey gets underway in the UK

Many years have passed since resistance surveys were last conducted in the UK to investigate the distribution of anticoagulant resistance in Norway rats. Now, a new survey is underway using the new DNA-sequencing technology. Samples will be collected from all the main known rat resistance foci by local authority pest controllers.

The sampling will be systematic to allow the spread of resistance away from a central point in the focus to be determined. The DNA analysis will be done at the Universities of Huddersfield and Reading. The project is funded by a consortium comprising rodenticide manufacturers and pest control trade associations.

New RRAG anticoagulant resistance guidelines published

RRAG has published a guideline document (see publications above) which sets out the current position on the occurrence and significance of anticoagulant resistance in Norway rats in the UK. For the first time, the document uses the latest DNA sequencing data to identify resistance mutations from the various UK resistance foci and explains the impacts of the different mutations on the efficacy of rodenticide active substances.

A New Resistance Mutation Identified in Kent

Following reports of the failure of bromadiolone to control rats on agricultural holdings in Kent, researchers at the University of Reading have identified the tyrosine139phenylalanine (Y139F) mutation in rodents taken from the site. Anticoagulant resistance was reported in Kent in Norway rats as long ago as 1968 but little has been heard from the area since comprehensive resistance surveys were last conducted in 1978.

The Y139F mutation is one of the most commonly found on the continent in France and Belgium but had never before been identified from rats in the UK. Research conducted on rats from France which carry this mutation shows that it confers a practical level of resistance to first-generation anticoagulants, such as chlorophacinone, and to the second-generation bromadiolone.

New DNA-sequencing technology for Rodenticide Resistance in the UK

Workers at the Universities of Huddersfield and Reading have been developing the newly-available DNA-sequencing technology for the identification of anticoagulant resistance in Norway rats and house mice. The technology was first used by workers in Germany and makes it no longer necessary to rely on expensive and slow resistance testing techniques based on feeding tests and blood-clotting response tests to identify resistant rodents.

Now that it is fully functional at Huddersfield and Reading, the DNA technology will be available for resistance research but will also be offered to pest control practitioners who are having problems controlling rodents using anticoagulants. Rat tail samples, which carry the required DNA, are taken and preserved and then submitted to the laboratories for testing. Results are normally available within a few weeks. For more information contacts are: Huddersfield d.j.clarke@hud.ac.uk and Reading c.v.prescott@reading.ac.uk