Show pyrethrum Is regarded as reliable insecticide wider use of pyrethrum and derris seems to be the answer to the growers need tor for keeping his leafy vegetables tree free from residues of the more toxic insecticides according to W 11 II white in charge of truck crop and garden insect investigations united states department part ment of agriculture chemists and entomologists of the department have long sought substances that could be depended on to protect growing crops against destructive insect pests and still leave nothing harmful to human beings on the product to be marketed he said although this difficult problem Is not yet completely solved the scientists working on it have found that minute quantities of two plant products derris and pyrethrum kill many insects feeding on truck crops and are less likely tuan than most inorganic insecticides now nou in common use to leave harmful residues |