Application of ECO₂FUME^® phosphine fumigant for the complete control of major stored product insect pests in milled rice in Thailand

ECO2FUME® phosphine fumigant was used to fumigate milled rice in a commercial plastic bag (5 kg) and milled rice in a jumbo bag (1,000 kg) under gas-proof sheets to assess its performance against a mixed-age culture of Sitophilus zeamais, Tribolium castaneum and Oryzaephilus surinamensis. The trials were divided into 2 groups: 1) milled rice in a commercial plastic bag (packed rice) treated with a 50 g/m3 ECO2FUME® application rate (700 ppm phosphine) for 2 days with two bag stacks of 46 m3 and 55 m3 and for 3 days with two bag stacks of 50 m3 each; and 2) milled rice in a jumbo bag (raw material rice) with stack size of 314 m3 treated with a 35 g/m3 ECO2FUME® application rate (500 ppm phosphine) for 3 days and a stack size of 435 m3 treated with 50 g/m3 ECO2FUME® application rate for 2 days. Gas sampling lines were installed in the stack to measure the phosphine concentrations during the fumigation period. The results of the fumigation trials showed that mixed-age cultures of the three insect species in packed rice stacks were completely controlled at 2 and 3 days when applied with an ECO2FUME® application rate of 50 g/m3, whereas most insects in untreated control cages remained alive. ECO2FUME® was also 100% effective in raw material rice stacks with complete control of mixed-age cultures of the three insect species using 35 g/m3 of ECO2FUME® for 3 days and 50 g/m3 of ECO2FUME® for 2 days. Commercial tarp fumigation of milled rice with ECO2FUME® can be fumigated successfully without “top up” with good sealing procedures. Gas monitoring at regular intervals throughout the whole fumigation period is part of best fumigation practice to ensure that the minimum recommended phosphine concentration is maintained for complete control of all stages of target insect pests.