A PRACTICAL TRIAL OF PYRETHRINS-IN-OIL SURFACE SPRAYS FOR PROTECTION OF BAGGED GRAIN AGAINST INFESTATION BY CADRA CAUTELLA (WLK) (LEPIDOPTERA PHYCITIDAE) IN KENYA

Two formulations of synergized pyrethrins in technical white oil were tested as monthly protective sprays on stacks of fumigated bagged wheat, primarily against Cadra cautella (Wlk.) but also against Sitophilus oryzae (L) and Tribolium castaneum (Hbst.), under warm-temperate storage conditions in up-country Kenya. The formulations were: 0·4% pyrethrins with 2·0% piperonyl butoxide, applied at 50 ml/m2, and 0·4% pyrethrins with 0·4% piperonyl butoxide at 20 ml/m2. Results were assessed by recording infestation in samples taken from each stack after 18 weeks storage and five spray applications. Both treatments gave reasonably good protection against C. cautella but were not satisfactory against S. oryzae or T. castaneum. There was no evidence of any taint in bread made from the treated grain, but the higher application rate caused excessive staining of the bags. It is concluded that satisfactory control of reinfestation by C. cautella can be expected in practice using 0·4% pyrethrins in oil with only a minimal quantity of added piperonyl butoxide, and that 20 ml/m2 is a suitable rate for application to bagged produce. © 1969.