EVALUATION OF A COMMERCIAL WAX-BOUND BAIT CONTAINING 0. 0375% COUMATETRALYL AGAINST RATTUS TIOMANICUS (MILLER)

LEE C.H. and MUSTAFA MD. D.

SUMMARY

Laboratory feeding tests with commercial wax maize baits were conducted to determine the susceptibility of Rattus tiomanicas Miller to coumatetralyl. No-choice feeding on 0.0375%coumatetralyl baits for the periods of two, four, six, eight and ten days gave mortalities of 25%, 65%, 90%, 95% and 100% respectively. Marked variation in susceptibility to coumatetralyl among the individuals was seen in the feeding tests. Sixty per cent of the animals succumbed to the poison between five and eight days showing symptoms of chronic poisoning. The lethat feeding period (LFP 50) was 2.9 (2.0-3.7) days for females and 3.2 (1.9-4.2) days for males. No significant difference (P > 0.05) was found between the mean of the two sexes. The mark variation in susceptibility of the animals with two males and one female surviving the six- and eight-day feeding period indicates the possible occurrence of resistant rats if field application of the poison was undertaken in the long term. Thus the LFP 99 level of 11.0 days would be a suitable test for detecting coumatetralyl resistance.

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