Laboratory assessment of the efficacy of phosphine and methyl bromide fumigation against all life stages of Liposcelis entomophilus (Enderlein)

Abstract

Liposcelis entomophilus is common and often very abundant in cereal stores in hot, humid areas, heavy infestations in South-East Asia being associated with phosphine fumigation. Tolerance of all life stages to phosphine fumigation was investigated under tropical storage conditions. Eggs were most tolerant and required a concentration of 1.7 mg l-1 for 5 days to kill 99% of the eggs, but this gas concentration would prove difficult to attain in a typical fumigation under gas-tight sheets. When L. entomophilus was exposed to methyl bromide over a range of concentration X time (CT) products at 27°C and 30% relative humidity, all life stages were controlled at 50 mg l-1 h-1. Higher CT products would be required to kill the most tolerant life stages of common stored-product pests, such as Tribolium castaneum but the CT products normally attained using gas-tight sheet fumigations are sufficient to kill L. entomophilus