Stabilization of pyrethrins for prolonged residual toxicity. I. Screening of various ingredients.

Various solvents, vegetable and essential oils, antioxidants and seed extracts were tested for their independent effect in stabilising the residual toxicity of pyrethrins to adults of Tribolium castaneum (Hbst.). Of the solvents tested, trichloroethylene, kerosene, chloroform, ethylene glycol monoethyl ether, carbon tetrachloride and mineral turpentine assisted in retaining the residual toxicity. Oils such as sesame, cotton seed, castor and cashew shell enhanced the activity of pyrethrins independently. Of the antioxidants, pyrogallic acid and hydroquinone, and among the seed extracts an aqueous extract of deoiled neem (Azadirachta indica), exhibited a stabilising effect on residues of pyrethrins, causing significant knockdown and mortality of the test insects.