Synergistic Effect of Phosphine and Carbon Dioxide on the Mortality of Tribolium castaneum (Coleoptera: Tenebrionidae) in Paddy

Phosphine (PH3) is widely used as a fumigant for the control of stored product pests. Indiscriminate use of PH3 leads to the development of resistant strains. Thus, an experiment was conducted in a laboratory scale fumigation chamber to determine the synergistic effect of carbon dioxide (CO2) and PH3 on the mortality of Tribolium castaneum during fumigation of paddy. PH3 gas generation varies depending upon grain moisture content and dosage of PH3 used for fumigation treatment. Thus, the maximum PH3 concentration with respect to saturation time was achieved when paddy were treated with 98% CO2 + 3 ppmPH3 at 17% moisture content, leading to a quick mortality of different life stages of T. castaneum with minimum LT50 and LT99 value. Among the different stages of T. castaneum, pupal stage was more resistant to all the treatments compared to larva and adult stages. PH3 residues in all the treatments were below the recommended level and it can be considered as safe for consumption.