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SOME ASPECTS OF THE EFFECT OF THE SOLVENT ON THE TOXICITY OF SOLUTIONS OF INSECTICIDE
Author(s) -
HADAWAY A. B.,
BARLOW F.
Publication year - 1958
Publication title -
annals of applied biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.677
H-Index - 80
eISSN - 1744-7348
pISSN - 0003-4746
DOI - 10.1111/j.1744-7348.1958.tb02190.x
Subject(s) - solvent , endrin , dieldrin , malathion , toxicology , organic chemistry , biology , pesticide , chemistry , agronomy
The effect of varying the solvent upon the contact toxicities of solutions of insecticides to mosquitoes and flies has been investigated using DDT, prolan, dieldrin, endrin and malathion. The insects were allowed to walk for a limited time on filterpapers impregnated with the solutions. Chemical structure of the solvents had a general influence upon the biological activity of the solutions. Providing that the physical properties of the solvents were similar, insecticides were more effective in paraffinic hydrocarbons than in aliphatic long‐chain esters and related compounds, and were least effective in aromatic esters. Physical properties of the solvents were of importance in determining the effectiveness of insecticides dissolved in a group of solvents of similar chemical structure. Viscosity was an especially reliable guide as it presumably controlled the rate at which the solution could pass from the paper and be absorbed by the insects during the exposure period. The order in which the solvents could be arranged with regard to their ability to influence biological action was the same for all the insecticides used, but the ratios of the median lethal concentrations in different solvents varied greatly from one insecticide to another. Consequently, the relative toxicities of the insecticides depended upon the solvent in which they were dissolved. When some of the solutions used in filter‐paper tests were applied topically to the insects the differences in effectiveness were greatly reduced, showing that an important influence of the solvents had been upon pick‐up of insecticide from the papers. However, even with topical applications there were still some differences in median lethal concentrations and especially in rates of action between the solvents, thus providing further evidence that the solvent is also concerned with passage of insecticides through the insect cuticle. The relative toxicities of the solutions bore no relationship to the solubilities of the insecticides in the solvents, and it was concluded that in these experiments chemical potential was not likely to be a controlling factor.