BIOLOGICAL ASSAY OF INSECTICIDAL SPRAYS

Abstract

MORE than a hundred and fifty different kinds of insects have been found from time to time on stored produce, but only a dozen or so are found often and in dangerous numbers. The control of these insects is a matter of considerable economic importance, more particularly when foodstuffs susceptible to attack by them are kept in store over prolonged periods and wastage must be avoided. The use of insecticidal sprays as a control measure, in warehouses where grain, dried fruits, cacao, etc., are stored, is comparatively simple and, when properly applied, has been shown by experience to be effective, provided the infestation has not been allowed to reach too great proportions. The Pest Infestation Laboratory of the Department of Scientific and Industrial Research is therefore carrying out a study of these insecticidal sprays as one of the chief items in its programme of research on ways of combating infestation of stored produce by insects. Special attention has been given to the development of a method of comparing the killing power of different sprays since it was evident that a comparative test of this kind was essential as the next step in the process of improving insecticidal sprays. The technique of the test which has been successfully worked out at the Pest Infestation Laboratory is described in the second half of this article.