Studies on the Toxicity Of insecticide Films

Publisher Website
Google Scholar
Abstract
Experiments are described in which the concentration-time-mortality relationships with certain insects were investigated for the insecticides DDT and γ-BHC, the insecticides being used in film form. Adults of Tribolium castaneum, the larvae of Plutella maculipennis and adults of the Aphid, Macrosiphoniella sanborni, were used as test insects. T. castaneum proved the most suitable insect for experimental laboratory work on films, since it can be kept in continuous contact with them without difficulty.A description is given of the techniques employed for T. castaneum and also for the other insects which are able to progress on perpendicular glass surfaces. Techniques are described for experiments in which attempts were made to eliminate as far as possible the fumigation effect of γ-BHC and to differentiate it from that of direct contact. The fumigation effect of this compound is considerable and it appears impossible to eliminate it entirely.With T. castaneum the characteristic curves connecting log. concentration with percentage mortality varies with time of exposure, from horizontal lines showing on the one hand zero toxicity and, on the other, complete mortality at all concentrations. Sigmoid curves are represented between these limits. The average survival period of T. castaneum adults gradually decreases with the strength of poison in the film.The surface upon which toxic films are deposited was shown in preliminary experiments to have a definite bearing upon their effectiveness. Waxed surfaces showed least toxicity, and amongst a few leaves used Geum gave the highest and water lily, at lower critical concentrations, the least effect. High concentrations on water lily were little different from others in toxic action.
Keywords