Phosphine is a safe and effective fumigant, claims study

Phosphine may be as effective as the ozone-depleting methyl bromide (MB) in killing insect pests and can be used as quarantine fumigant at ports, according to a study by the Indian Council of Agricultural Research (ICAR) scientists.

According to Sumitra Arora, Director of the New Delhi-based National Centre for Integrated Pest Management, a lab affiliated to the ICAR, who led the two-year-long study, the results have already been submitted to the Ministry of Agriculture, which sponsored the study.

Thorough study

Scientists from NCIPM and other ICAR institutes conducted experiments in four different agro-climatic locations using grains such as wheat and rice as well as pulses. “We found that phosphine is 100 per cent effective against the pests,” she told a conference here last week. Phosphine, a fumigant in a gaseous form, is normally produced using aluminium phosphate as substrate.

Even though India, under the Montreal Protocol it signed and ratified, was committed to phase out MB and other ozone-depleting substances (ODS) by 2015, the fumigant is still used at Indian ports for treating cereals and pulses imported from other countries to quarantine insect pests.

“The government has been extending the permission to use MB at Indian ports every six months and the approval is currently valid till June 20 this year,” said Ujjwal Kumar, a senior official with the chemical firm UPL at the conference.

Kumar, who is head of fumigant business for India and South East Asia at UPL, said 95 per cent of the countries in the world have phased out MB and only India and a few South East Asian countries currently permit the use of MB. The fumigant is said to have 60 times ozone-depleting potential than refrigerant chloroflurocarbons, which has already been phased out globally.

“India has been penalising those who are exporting food products without treating them with MB and this has been an issue of contention in many bilateral trade deals,” Kumar said.

According to him, shipments to India not pre-treated with MB are fumigated with MB offshore or onshore, but by levying five times the cost of fumigation from exporters as penalty. “While many major economies were getting away with putting pressure on New Delhi, others have no choice but pay the penalty,” Kumar said.

Current phosphine use

It is not that India has not been using phosphine as fumigant. As it banned the use of MB in domestic warehouses, phosphine is used in its place. This is because of MB is not good for repeated use as it leaves residues in the grains.

“The grains stored in warehouses need to be fumigated every three months and phosphine, which has no residual build-up is preferred for this,” said Chitra Srivastava, professor emeritus of entomology at the Indian Agricultural Research Institute in New Delhi.

According to S Rajendran, former scientist at the Mysuru-based Central Food Technological Research Institute, one of the reasons why MB is preferred as quarantine pest fumigant is that it is fast-acting. “While MB is capable of killing pests like grain borers, beetles and weevils in less than 24 hours, phosphine takes almost five days. Time is money in export-import business,” Rajendran said.

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