COMPARATIVE EFFICACY OF 2 METHODS OF DELIVERING AN ANTICOAGULANT RODENTICIDE TO 3 SPECIES OF SOUTH ASIAN RODENTS

The efficacy of two methods, namely contact poisoning (during which an imals ingest poison during grooming of fur and feet) and poison baitin g (during which animals ingest poison during feeding), of delivering a rodenticide, Racumin (coumatetralyl), to three species of South Asian rodents, Bandicota bengalensis, Tatera indica and Rattus rattus, was determined in laboratory and field experiments. Species-specific diffe rences occurred between the efficacy of 0.75% Racumin tracking powder (RTP) used for contact poisoning, and 0.0187, 0.0375 and 0.075% Racumi n baits (RE), prepared by mixing the concentrate with cracked wheat, p owdered sugar and peanut oil (96:2:2), used for poison baiting. B. ben galensis was most susceptible to the toxic effects of Racumin as both RTP and RE caused 80-100% mortality after short exposures (15 min and 3h) to a floor/runway treated with 1 g/rat of RTP in forced contact an d simulated runway techniques and 1-2 days of choice feeding of 0.0187 and 0.0375% RE in feeding tests. These treatments were less effective against T. indica and least effective against R. rattus. In pen exper iments, in which the runway was treated with 2g of RTP, 100 and 60% mo rtality om groups of 5 rats each of B. bengalensis and T. indica occur red, respectively. Dusting of 0.75% RTP on runways and within burrows of rodents, with a puff duster, resulted in 62.7% control in maturing wheat fields, 56.1% in wasteland areas and 38.6% in bunds between crop fields. Application of 0.0375% RE within burrows resulted in 66.1 and 67.9% rodent control in maturing wheat fields and field bunds, respec tively; the corresponding values with 2% zinc phosphide bait were 52.9 and 80.6%.