Optimizing phosphine applications for insect control in Bagged rice stored in Indian warehouses

Phosphine, considered a viable substitute for methyl bromide amid its global phase-out, requires assessment for fumigation efficacy in India due to limited reports on its field applications. This study assessed phosphine's effectiveness against stored grain insects by stacking 150 tonnes of rice into 30 stacks (5 tonnes each), replicated thrice with including same number of controls. Target insects included Tribolium castaneum (Herbst, 1797) (Coleoptera: Tenebrionidae), Sitophilus oryzae (Lin, 1763) (Coleoptera: Curculionidae), and Rhyzopertha dominica (Fab, 1792) (Coleoptera: Bostrichidae) across three locations. Two aluminium phosphide (AlP) formulations (56% at 2 and 3 tablets/tonne; 77.5% granule at 1.0 and 1.5 g phosphine/m³) were tested with 7- and 10-day exposures at all locations. Insects were monitored for 60 days post-treatment, achieving 100% mortality except for the field population of T. castaneum at Cuttack. Phosphine at 500–700 ppm could effectively control all insect stages in untreated infested grains at 1.5 g/m³ phosphine gas following 7 days exposure at 28–36 °C and 52–80% humidity. Cumulative Ct values ranged from 264 to 332 g h/m³, with 15–16% gas dissipation across locations. Phosphine proved effective for rice storage pest control.