Efficacy studies on ECO₂FUME® phosphine fumigant for complete control of Sitophilus zeamais and Tribolium castaneum in stored maize

ECO2FUME® fumigation of maize bag stacks under gas proof sheets was conducted to establish the optimal dosages (application rate) and exposure times (fumigation period) against mixed-age cultures of Sitophilus zeamais and Tribolium castaneum. The Complete Randomized Design (CRD) experimental design was employed, with 3 replications and 4 treatments. The experiments were divided into three groups: 1) treatment with a 25 g/m3 ECO2FUME® application rate (350 ppm phosphine) for 3, 4, and 5 days and a control treatment; 2) treatment with an ECO2FUME® application rate of 50 g/m3 (700 ppm phosphine) for 2, 3, and 4 days and a control treatment; and 3) treatment with a 70 g/m3 ECO2FUME® application rate (1,000 ppm phosphine) for 1, 2, and 3 days and a control treatment. The three target phosphine concentrations of 350 ppm, 700 ppm and 1,000 ppm were maintained during the whole fumigation period. Results of the studies showed that no insect was alive at all dosages and exposure times. The studies also indicated that fumigation with ECO2FUME® could reduce the fumigation period by increasing the phosphine concentration. The effective fumigation protocols on maize against mixed-age cultures of S. zeamais and T. castaneum were ECO2FUME® application rates of 25 g/m3 for 3 days, 50 g/m3 for 2 days and 70 g/m3 for 1 day. The target phosphine concentration must be maintained throughout the fumigation period to achieve 100% mortality of all stages of insects.