Stabilization of pyrethrins for prolonged residual toxicity. II. Development of new formulations.

In further investigations on the formulation of pyrethrins for prolonged action against adults of Tribolium castaneum (Hbst.), a mixture of pyrethrum extract (containing 20% pyrethrins) at 1%, with 2% sesame oil, 1% pyrogallic acid, 1% beeswax, 7.5% Niogen X-1250 (a non-ionic emulsifier) and 29% trichloroethylene, and a similar formulation with, in addition, an aqueous extract of de-oiled neem seed (Azadirachta indica) at 1% were as effective in laboratory tests as a standard formulation of pyrethrins with piperonyl butoxide at 1:10; the formulations retained their effectiveness for 8-10 weeks.