Influence of relative humidity on phosphine concentration during aluminium phosphide (ALP) fumigation¬ in pigeon pea

Abstract

Phosphine fumigant is widely used to control stored insect pest infestation in grains. The study on Aluminium Phosphide (ALP) fumigation was conducted to find out the effect of relative humidity on concentration of phosphine. Aluminium phosphide (tablet) 56% formulation was used for fumigation of two stacks of pigeon pea grains, each of 4 MT capacities. During fumigation first stack the humidity was ranged 60 to 70% and another stack the humidity was between 50 to 60%. Fumigation procedure carried out as per National Standards of Phytosanitary Measures (NSPM) with dose rate of 3 tablets / MT for 10 days exposure period. Phosphine concentration was monitored in both stacks from 1 to 10 days after fumigation. After 24 hrs (1 day) of treatment the average phosphine concentration was 340 ppm in stack with higher humidity and terminal concentration (after 10 days) was 315 ppm, whereas in stacks with lower humidity the concentration was 309 ppm and 184 ppm after 24 hrs and 10 days respectively. The results revealed that concentration of phosphine was directly proportional to the humidity.