A Method of assessing the acaricidal Properties of DDT and “Gammexane” Preparations in Field Trials

Abstract

DDT and “Gammexane” have many advantages over arsenic as acaricidal agents.The sites of attachment of the common tick species on bovines are recorded and the killing properties of various dilutions of DDT and “Gammexane” are assessed by observations on R. appendiculatus attached on the ears and A. variegatum attached on the udder and flanks of cattle.The preparations were usually applied as sprays by means of a flit-gun, an Aerograph spray gun, and Kent sprayer or “Solo” hand pump. A “swirling-jet” nozzle was found most suitable. A possible combined spraying-dipping method using a shallow bath is also described.In preliminary experiments, a spray containing 2·5 per cent. DDT and a preparation containing 1:10 of the “Gammexane” dispersible powder P.530 killed all ticks attached at time of spraying but the residual effects were lost about the 4th day after spraying. Field experiments gave similar results, but 1:20 of the P.530 powder (0·325 per cent. active gamma) proved equal in killing value to the 1:10 preparation.The addition of coumarone resin did not increase the residual effects of a 2·5 per cent. DDT emulsified solution.