Propylene oxide: a fumigant for quarantine purposes as a potential alternative to methyl bromide

In this study, PPO at low pressure (100 mm Hg) was tested in his study for rapid disinfestation of durable stored products as replacement for methyl bromide by evaluating its toxicity to confused flour beetle (Tribolium castaneum (Herbst)) in present of various commodities, its sorption and residue on various commodities. It required a dosage of 19.9, 24.1, 47.4 and 83.4 mg/l to kill 99% of the pupae of T. castaneum when fumigated in empty space and in presence of wheat, cacao beans and corn, respectively. Thus, much higher dose of PPO required for PPO fumigation in presence of corn and cacao beans to obtain the complete mortality of the pupa of T. castaneum. Sorption of PPO by corn, wheat and cacao bean after 4-h exposure time was relatively high, varying from 57% to 79% of initial concentration. The greatest sorption of PPO for 4 h exposure period was observed by corn (79%). The PPO residue in corn, cocoa bean and wheat were a maximum average of 157, 117 and 133 ppm respectively at 0-1 day after termination of aeration, which all were below the 300 ppm maximum tolerance. Based on its high and rapid toxicity to insects, its reasonable sorption by the commodities and its rapid desorption from the commodities, the combination of PPO with low pressure can be a potential as fumigant for replacing alternative methyl bromide for quarantine purposes.