Effectiveness of closed-loop systems for phosphine fumigation of large scale grain storages in China

Abstract

The effectiveness of closed-loop phosphine fumigation was tested in two large, horizontal warehouses and one large round, squat grain storage in China. Phosphine was applied as aluminium phosphide tablets placed on the surface of the grain or with a generator. Each storage was tested for gas-tightness and phosphine concentration was monitored during the fumigations. The pressure decay half-lives, 500 to 250 pa, were 48-60 seconds for the horizontal storages and 200 seconds for the circular squat storage and the dosage of aluminium phosphide tablets was 1.5-2.0 g/m3 (releasing 1.5-2.0 g PH3/m3). Phosphine concentration was maintained at greater than 100, 150 and 200 ml/m3 for more than 18, 16 and 6 days, respectively. The loss of phosphine from the storage was only 3.6-4.2% per day. These concentrations should be sufficient to control completely all insect pests including known resistant strains.