Control in Resistance Foci

It is important to understand that all known resistance mutations, in both rats and mice, are capable of effective control with applications of the most potent second-generation anticoagulants, brodifacoum, difethialone and flocoumafen, and that no practical resistance to any of these active substance is presently known.

It is more important than ever that complete eradication of rodents is achieved at resistance sites. This is best done using an integrated strategy which employs a combination of effective interventions, including the use of non-anticoagulant rodenticides, where these are available, as well as effective anticoagulants. Where residual rodent activity is identified after anticoagulant use, and this cannot be eradicated using other chemical interventions, apply intensive trapping to eliminate remaining rodents. Gassing or fumigation should be considered, provided it is carried out by personnel with appropriate expertise. New techniques of trapping and remote detection and monitoring should be considered to eradicate remaining infestations, and to prove the success of the control measure.

Where individual infestations are found to be resistant, or to contain resistant individuals, it is possible that the resistance extends beyond the treated site and onto neighbouring properties. Where there are indications that resistance may be more extensive than a single infestation, apply area or block control rodent programmes if possible. The area under such management should extend at least to the boundaries of the area of known resistance and ideally beyond. These programmes must be effectively coordinated and should encompass the procedures identified above. Carefully record the details of all measures employed so that useful local knowledge is accumulated about effective and ineffective resistance management strategies.

Do not use anticoagulant rodenticides as permanent baits as routine. Use permanent baits only where there is a clear and identified risk of immigration or introduction or where protection is afforded to high.