Improved speedbox as an effective instrument for phosphine fumigation

Abstract: Phosphine is mainly in use today for stored product insect pest control, after the phase out of methyl bromide in developed countries due to its ozone depletion effects. However, some limitations, such as low temperatures and relatively long exposure time, limit the use of phosphine. In order to overcome these difficulties, a special devise, called “speedbox” has been developed by Detia Degesch GmbH, Germany. Currently, the improved model of speedbox was evaluated for phosphine fumigation against stored product insects. The experiments were conducted in a fumigation room (15 m3) and in commercial container. Internal coleopterans Sitophilus oryzae, Rhyzopertha dominica and Callosobruchus maculatus and external coleopterans Oryzaephilus surinamensis, Trogoderma granarium, Tribolium castaneum and lepidopterans Plodia interpunctella and Ephestia cautella were used as test insects. All developmental stages of these species were tested. The used phosphine concentrations were 2-8 g of gas/m3. Exposure time was 2 to 4 d. The phosphine concentration was monitored by Bedfont device model 415 and Draeger tubes. Three phosphine gas sampling points were located at the top, middle and bottom of the fumigation room while one point was placed among the bags containing wheat or chickpeas. The temperatures of intergranular air and of the room space, as well as outdoor air relatively humidity were also recorded. At 4 g/m3, the phosphine concentrations of 370 ppm, 1100 ppm and 2000 ppm (a maximum of the monitor range) were reached just after one, 3 and 9 h from the beginning of the fumigation, respectively. At 6 g/m3, the concentrations of 1000 ppm and 2000 ppm were reached just after 3 and 6 h, respectively.The total mortality of all tested insects and stages was recorded. In the commercial container fumigations similar results were obtained. The use of improved model of speedbox allows reaching higher by 20-30% phosphine concentrations, getting effective concentrations in a shorter time compared with the basic model and especially with the application of tablets and thus decrease the exposure time of the fumigation. The speedbox also allows to achieve an even distribution of the gas in the treated space and to enable effective fumigation at low temperatures. The use of the speedbox opens novel possibilities for phosphine fumigation also as a quarantine treatment.