Issues in Phosphine Fumigation

Phosphine gas released from metal phosphides is unique having a worldwide acceptance as a fumigant of choice for disinfestation of stored grains and other commodities, to facilitate domestic as well as international trade because of ease of application, low cost and effectiveness. Safe and effective fumigations with phosphine will result only if fumigations are carried out diligently by trained operators, adopting sound working procedures like application of correct lethal concentration sufficient enough to kill target pests in a well-sealed good quality enclosures and adoption of a prescribed exposure period, which cannot be compromised even by increasing the dosage. However inefficient operations and control failures because of phosphine application in leaky structures, provision of sub lethal dosage, lesser exposure period and non- availability of alternate fumigants are becoming a serious threat to dominance of phosphine. Effective and efficient fumigation requires strict adoption of laid down protocol to avoid failures of fumigation and development of insect resistance against stored grain pests. Proper application of phosphine gas is good enough to kill all stages of insects including the eggs. The toxicity of phosphine is however based on rate of respiration that is why the susceptibility of insect life stages to phosphine is in the decreasing order adult > larva > pupa > egg. Few myths are prevalent amongst Indian bagged cargo fumigators like method of distribution of phosphine generating metal phosphide tablets in stacks, wetting of tablets to get faster release of phosphine, compromising the exposure period and other related issues. Besides it is necessary to understand the role and system of governing fumigation system by regulatory authorities. Keeping in view the highly toxic nature of phosphine and absence of any specific antidote, few suggestions for safety of operators are highlighted. This review is prepared to understand various issues and myths in application of phosphine, which may even help to overcome development of resistance.