Alternatives to Phosphine Fumigation of Stored Grains:The Indian Perspective

Out of a total about 10% post-harvest loss of grains, a significant 6% are damaged during their storage. Fumigation of the stored grains is considered indispensable to check this avoidable loss. Methyl bromide (MB), a cheap, broad spectrum fumigant, has to be phased out honouring 'Montreal Protocol'. Phosphine widely used worldwide, is the only fumigant currently used in India, because of its low cost, availability and residue-free treatment. But one serious limitation of use of phosphine is development of resistance in the major stored grain insect-pests. There are several other fumigants like sulfuryl fluoride, propylene oxide, carbonyl sulphide, ethyl formate, hydrogen cyanide and methyl iodide which have been found promising but cost remains a serious factor, especially for a country like that of India. Beside fumigants, use of Modified Atmospheres (MAs) seems to be the best bet for pesticide free organic storage. However, the technology of MAs can be well adapted where cheap sources of nitrogen or carbon dioxide are available and the storage structure is well sealed. Biogas, produced from the cow dung at farm level in many households of Punjab (India) has shown promising results to control the insect-pests in stored grains and pulses without affecting their germination and quality. Ozone, a strong oxidant, has also been successfully tried for control of stored grain insect pests, but its corrosive property towards most of the metals, is a concern. Though many volatile plant oils have proved quite effective to check the stored grain insect-pests but lack of systematic toxicological data has limited their use as practical agents for the safe storage of food grains. In the present scenario, it seems worthwhile to continue to use phosphine as fumigant for the control of stored grain insect-pests with its improved formulations exercising all the precautionary measures, till a new one equally competent is made available. Further, experimentation with other new fumigants should be continued to explore their potential. There is need to undertake further field level trials with biogas in the stored grains.