Ethylene Dibromide: Methyl Bromide Mixtures as Fumigants against the Confused Flour Beetle1

Abstract

Five different mixtures of ethylene dibromide and methyl bromide were studied at three dosage levels, 8, 10, and 12 mg./l., for effectiveness as fumigants against different life stages of the confused flour beetle, Tribolium conjusum Duv., including adults, larvae, and pupae. Eggs were included in early experiments but were omitted in later ones, since at the dosages studied, 100% mortality of this stage was characteristic for all treatments. The insects were exposed to fumigant for a 5-hour period, and mortality counts were made at 1, 2, and 14 days following completion of exposure. The effect of fumigation on larval emergence from eggs laid by adults surviving treatment was also studied. Most of the mixtures investigated were more effective against all life stages of the insect studied than was methyl bromide alone. In addition, many of the mixtures were more effective than either ethylene dibromide or methyl bromide, on the basis of mortality 1 day following exposure to the fumigant. Thus, insect kill is more rapid with mixtures than with either component alone. Larvae emerged from eggs laid by adults surviving treatment at all dosage levels of methyl bromide, and of mixtures containing less than 1.0 mg./l. of ethylene dibromide. No larval emergence was observed from eggs of adult beetles surviving treatments containing more than 1.0 mg./l. of ethylene dibromide. Advantages of the mixtures for practical fumigation are apparent from results of this study.