A DIRECT‐SPRAY TECHNIQUE FOR THE BIOLOGICAL EVALUATION OF PYRETHRUM‐IN‐OIL INSECTICIDES FOR USE AGAINST STORED PRODUCT INSECTS IN WAREHOUSES

Abstract

A direct‐spray technique for the biological assay of pyrethrins in Shell oil P31 is described, together with the experiments leading to its adoption. The technique is such that film effects are reduced to the minimum practicable, but it is otherwise as similar as possible to the film technique described by Parkin & Green (1943). Methods for statistical analysis of the results are discussed. For the biological assay of pyrethrins in Shell oil P31, the direct‐spray method is slightly superior to Parkin & Green's film method, but both techniques should have their uses in general experimental work.