Evaluation of Synergized Pyrethrum for the Control of Indian-Meal Moth in Stored Shelled Corn

Excerpts from the report Introduction: Changes in grain handling and grain storage practices in the past few years have resulted in the storage of grain for much longer periods of time, sometimes up to 5 years. The reserve stocks of grain, particularly of corn which is not otherwise commercially stored in large quantities as shelled corn, have required new and improved methods of protection from insect invasion. The Indian-meal moth (Plodia interpunctella Hbn.) has been especially troublesome in shelled corn stored in wood or metal bins with capacities of 3,000 to 3,250 bushels. This species does not penetrate deeply into the grain bulk, confining its activities chiefly to the surface layer of grain where the larvae feed on the germ and spin unsightly webs on the surface. In line with the demand for improved control measures for this species, studies were begun at the Watseka, Ill., experimental corn storage site, in the summer of 1956, to explore the possibility of applying an insecticide directly to the top surface of the shelled corn to prevent further development of an existing infestation. This report presents the results of the first year's tests with a synergized pyrethrum spray applied to the surface of the grain at different dosages and at different frequencies. The study is still in progress, but due to the interest in this approach, the results through December 1956 are being presented now.