FIELD EVALUATION OF SINGLE AND MULTIPLE DOSE ANTICOAGULANT RODENTICIDES IN REDUCING RODENT POPULATIONS AND DAMAGES IN COCONUT PLANTATIONS

Comparative efficacy of brodifacoum, bromadialone (second-generation single-dose anticoagulant) was evaluated in a coconut crop on Minicoy Island. Pre- and postrodent control relative levels of rodent populations and damages were recorded as indices for assessing effectiveness of different concentrations and different bait formulations of three rodenticides. The black rat, Rattus rattus (Linnaeus), constituting a new record for Minicoy Island, was the predominant rodent species infesting the coconut crop. On an average, application of brodifacoum (.005% and .002%), bromadialone (.005% and .002%) and warfarin (0.025%) reduced rodent populations by 74.5, 73.58, 79.1, 69.16 and 68.44% respectively, resulting in reduction of rodent damages to nuts by 74.93, 70.26, 78.24, 69.53 and 61.9% respectively. However, brodifacoum (.005%) impregnated with rice and coconut oil controlled rodents by 86.88% with reduction in damages by 82.85%. It was followed by bromadialone (.005%) mixed with rice and coconut oil giving 86.48 and 83.33% control of rodents and damages, respectively. Except in the case of brodifacoum (.005%), where pulse baits were more effective than ragi baits, the effectiveness of baits followed the order of rice>ragi>pulse. Similarly, coconut oil proved to be best attractant followed by groundnut oil and palm oil. Results of these field rodent control studies are compared with field/ laboratory evaluations of respective rodenticides on Rattus rattus.