The Campaign for Responsible Rodenticide Use (CRRU) is appealing to pest controllers, farmers and gamekeepers for samples so that free DNA testing for rodenticide resistance in rats and mice can take place.

CRRU chairman Dr Alan Buckle said that without more testing, 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,” he said, “others may be using resistance-breaking products unnecessarily. Only more samples can solve this.”

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

Leader of CRRU’s Monitoring Work Group Richard Moseley said 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.