Toxicity of Certain Synthetic Organic Compounds to Insects

Abstract

THIS subject is discussed in the Canadian Journal of Research, June 1948, in a paper divided into two parts. In Parts Messrs. A. W. A. Brown, D. B. W. Robinson, N Hurtig and B. J. Werner record their result from testing the general toxicity of some 127 synthetic compounds when mixed in graded concentrations in the food of the larvæ of the housefly (Musca domestica), the confused flour beetle (Tribolium confusum), the Mediterranean flour moth (Ephestia Kuhniella) and adults of the granary weevil (Sitophilus granaria). Each compound was intimately mixed with the food medium in which each of the foregoing insects lives and feeds. The method of testing gives an overall measure of the contact, stomach, and fum-igant action of each compound without distinction as to its mode of action. The most highly toxic substances were found to be 'Gammexane' (the gamma isomer of hexachlorocyclohexane) and chlordane (obtained by the distillation of technical chlordane). The toxicity of D.D.T. was, on an average, one half of that of these two compounds. In Part 2 Messrs. A. W. A. Brown, B. J. Werner and F. E. Park record the results of their experiments regarding the direct toxicity of 91 compounds against the nymphs of the German cockroach (Blatella germanica) and of the large milk-weed bug (Oncopeltis fasciatus), continuously reared in the laboratory on seeds of Asclepias syriaca, and also adults of the confused flour beetle (Tribolium confusum). The compounds used were dissolved in graded concentrations in a benzine-kerosene mixture and sprayed on the insects confined in a cylindrical glass spraying tower 29 in. high. Compressed air was applied to an atomizer at a uniform pressure of 23 cm. mercury. Taking the results with the three species of insects as a whole, the highest contact toxicity was shown by 'Gammexane' and chlordane. Dinitro-o-cresol and dinitrocyclohexyl-phenol were next in order of effectiveness. The results described in the two parts of this paper are based on tests carried out at the Experimental Station, Suffield, Alberta.