Experiments in the Use of Insecticides for the Protection of Grain in Storage

Abstract

Five experiments in the use of insecticides against Calandra oryzae (L.) in stored maize are described. The results with statistical analysis and deductions are given. The insecticides used were BHC, DDT, pyrethrum, pyrethrin-piperonyl butoxide mixtures; the diluting dusts used were a local diatomite, a local bentonitic clay, and a local soapstone.Among the chief conclusions are the following:—The insect damage in conditioned grain did not reach, throughout an eight-month period, the high level which it did in unconditioned grain, the conditioning process alone therefore is a valuable treatment for insect control.Bentonite alone is not a protectant and its addition to grain may on the contrary provide a more favourable environment for Calandra.A Kenya soapstone (from Kisii) is not an effective protectant but had some effect in reducing Calandra populations over the period when an initial increase was occurring in control bags.Kenya diatomite is a protectant. It reduces the percentage of grain damaged, but when used in bagged grain this is not proved to be due solely to intrinsic toxicity, but may in fact be due chiefly to the slippery nature of the material inhibiting insect distribution through the bulk of grain.Gamma BHC at 1 p.p.m. is completely effective for 16 months.Gamma BHC at 0.5 p.p.m. has some protectant effect but is not fully effective.DDT at 7 p.p.m. has not a protectant effect.