The Susceptibility of Laboratory-Reared and Field-Collected Cultures of Tribolium confusum and T. castaneum to Ethylene Dibromide, Hydrocyanic Acid, and Methyl Bromide1

Abstract

Field cultures of Tribolium castaneum (Herbst) and T. confusum Jacquelin duVal were obtained from various flour and feed mills and warehouses in the United States, and their relative susceptibility to fumigation with ethylene diibromide, hydrocyanic acid (HCN), and methyl bromide was compared with laboratory strains which had a history of no insecticidal treatments for a period of 10–15 years. Of 10 field-collected cultures of T. castaneum, 9 showed no evidence of increased tolerance when fumigated with ethylene dibromide, HCN, or methyl bromide. One culture of T. castaneum from Minneapolis, Minn., was significantly more difficult to kill with HCN than the University of California, Riverside, laboratory culture, but not with ethylene dibromide or methyl bromide. Of 7 field-collected cultures of T. confusum, 6 showed no evidence of increased tolerance when fumigated with ethylene dibromide, HCN, or methyl bromide. One culture of T. confusum from Buffalo, N. Y., was significantly more difficult to kill with ethylene dibromide and HCN than the University of California, Riverside, laboratory culture but not with methyl bromide.