Phosphine fumigation of sunflower seeds: efficacy on insect pests and phosphine residues in seeds
Abstract: A study was conducted on the phosphine fumigation on sunflower seeds, in order to control insect infestation, in collaboration with the National Laboratory of Stored Foodstuffs (French Ministry of Agriculture). It was performed on two kinds of fumigations: Fumigation during storage that eliminates all stages of insects with a PH3 standard dose 1.5 g/m3, and fumigation just before bin downloading, including low-dose shock action removes only adults (PH3 dose between 0.045 and 0.09 g/m3) for foodstuffs for sale to be processed (effective control persisting during two weeks).In order that the residual concentration of phosphine fell below the maximum residue limit in seeds (10 μg/kg), the waiting time required was variable according to the conditions of temperature and duration of the fumigation. Thus, in the case of fumigation during storage at 1.5 ppm g/m3, it takes between 3 and 30 days for complete phosphine desorption. For the fumigation just before unloading at 0.045 to 0.09 g/m3, no phosphine residues can be detected after 24 hours, whatever the temperature. For a good efficiency of phosphine gas, the temperature of the seeds should be at least 10 °C. These two types of fumigation showed very good control of insects found in sunflower seeds. They may be integrated in IPM (Integrated Pest Management) programs for oilseed protection against possible infestation by some insect pest species.