The toxic action of phosphine: Role of carbon dioxide on the toxicity of phosphine to Sitophilus granarius (L.) and Tribolium confusum DuVal

Carbon dioxide was found to potentiate the action of phosphine against a normal strain of Tribolium confusum and normal and resistant strains of Sitophilus granarius so that the length of the exposure period could be reduced. Studies on respiration showed that there was a 20 per cent increase in oxygen consumption in the presence of 4% carbon dioxide but no further increase up to 64% carbon dioxide level. Phosphine uptake on the other hand increased steadily with increase in carbon dioxide level and there was a concurrent increase in toxicity up to three-fold. Carbon dioxide enhanced toxicity when applied simultaneously with phosphine but not when applied before or after phosphine treatment.