Abstract
The effect of formulation on the toxicity of DDT to the adzuki-bean weevil, Callosobruchus chinensis, L. and the flesh fly, Sarcophaga peregrina ROBINEAU-DESVOIDY wasstudied. Three proprietary wettable powder formulations, three proprietary emulsifiable concentrates and a laboratory prepared DDT-acetone emulsifiable concentrate were included in this study. Suspensions or emulsions of these formulations in water were applied by means of a settling-mist tower either directly on the adult flies and weevils, to measure contact toxicity, or on lacquered paper discs which when placed in a cage with the adult insects measured the residual toxicity. The median-lethal concentrations of the formulations based on their p, p'-DDT content were calculated. The use of the emulsifiable concentrates resulted in greater contact toxicity than did the wettable powders. However, residues of the wettable powders were more toxic than all of the emulsifiable concentrates except a paste formulation which was equally toxic to the adzuki-bean weevil.
A study was also conducted on the effect of various solvents on the contact and residual toxicity of p, p'-DDT to the adzuki-bean weevil. When applied directly to the weevil without DDT, kerosene, α-methylnaphthalene, and cyclohexanone caused 100 per cent mortality Xylene solutions of DDT were as effective contact poisons as the water emulsions, but an acetone solution was less effective than the DDT-acetone-water emulsion. None of the solutions produced appreciably toxic residues.
