When working on sites where there is resistance, analysis of the specific resistance mutation present will permit the most effective rodent management strategy to be implemented. This strategy will include a requirement diligently to follow best practice guidelines and rodenticide label use recommendations. If in doubt, seek expert advice on the local circumstances either from manufacturers, distributors or from relevant government organisations.
If all other causes of treatment failure are ruled out, but confirmation of resistance by DNA-sequencing is not possible, or is not possible in a reasonable period of time, a sensible strategy is to apply an integrated approach to rodent pest management at the site (see also Rodent control), including if necessary the application of a product containing one of the most potent anticoagulants, brodifacoum, difethialone and flocoumafen or a non-anticoagulant.
When dealing with resistant Norway rats, and the nature of the resistance mutation present is known, recommendations for which anticoagulants rodenticides are effective against specific mutations are shown in Table 4 and Table 5. It is recommended to use products containing the respective compounds at the highest active substance concentration authorised for use against these rodent species.