Field trials of flocoumafen against warfarin-resistant infestations of the Norway rat (Rattus norvegicus Berk.).

The anticoagulant rodenticide flocoumafen was tested against warfarin-resistant Norway rats (Rattus norvegicus Berk.) infesting farm buildings. Complete control was obtained in 10-21 days (mean 14.2 days) in six treatments in which baits poisoned with 0.005% flocoumafen were maintained, in surplus, until rats ceased to feed from them. A further six treatments, in which the application of poisoned bait was restricted to periodic placements of 50 g, were also completely successful in 15-30 days (mean 21.0 days). Less poisoned bait was used in the restricted flocoumafen treatments than in the unrestricted treatments but the time taken to control the rat infestations was significantly longer.