Free DNA testing for rodenticide resistance in rats and mice has resumed with the Campaign for Responsible Rodenticide Use. Chairman Dr Alan Buckle calls for tail samples of freshly killed rats and mice from farmers, pest controllers and gamekeepers who think they may have resistance problems.

“The spread of resistance can only be tackled if we know where it is, and we are entirely dependent on people using this service for the data we need,” he says.

“Otherwise, pest controllers, farmers and gamekeepers could be using products that are ineffective in places where rodents are resistant. And where resistance genes are still absent, others may be using resistance-breaking products unnecessarily. Only more samples can solve this.”

The DNA tests will be conducted by the Animal and Plant Health Agency (APHA), Weybridge, Surrey. In addition to aiding rodenticide choices, Dr Buckle says this new collaboration with APHA enables CRRU to fulfil its resistance monitoring commitment under the UK Rodenticide Stewardship Regime.

Details how to collect, store and send samples to APHA are available at

Leader of CRRU’s Monitoring Work Group Richard Moseley says a serious concern is the almost complete lack of data from central England and most parts of Scotland, Wales and Northern Ireland.

In the past two years, new hotspots of rats with resistance genes have been found in Northumberland and County Durham, Tyneside and North Yorkshire, Devon and East Anglia, Greater Manchester and along the River Severn valley from north-west Shropshire to Somerset. Going back a number of years, resistance genes have become widespread across central southern England.