As the 2005 phase-out of methyl bromide approaches, international interest in potential alternatives to the widely used fumigant has reached an all-time high.

More than 250 researchers, Extension professionals, farmers and industry representatives from 40 countries attended the recent International Conference on Alternatives to Methyl Bromide held in Sevilla, Spain.

Senior officials from the Spanish government, which sponsored the conference, noted an unprecedented integration of public and private research to ensure international compliance with the Montreal Protocol, which obligates developed nations to stop using the ozone-depleting fumigant by 2005. Developing nations will be given more time to find a replacement.

During the past several years, methyl bromide has played a key role in protecting crops against root-eating nematodes, soil-borne diseases and weeds. In post-harvest applications, methyl bromide is used to protect against pests in stored foods, mills and food processing plants. The current phase-out, however, has resulted from the EPA's concern that methyl bromide may be contributing to the depletion of the ozone layer. As a result, intensive research has been conducted to develop alternatives for these use patterns.

Multiple alternatives

Seventy-two experts from 26 countries discussed their research at the international conference, and attendees learned that multiple alternatives are showing promise, both in crop production and post-harvest uses.

The fumigant 1,3-D, especially when used in combination with chloropicrin, has been the subject of extensive research. Several papers at the conference told how new application techniques such as drip fumigation, deep shank and broadcast have shown good efficacy against nematodes, diseases and some weeds. Some uses may require combination with a herbicide. Telone products developed by Dow AgroSciences contain 1,3-D and chloropicrin.

Several alternatives are showing promise for post-harvest protection. These include the use of heat, carbon dioxide and chemical fumigants. Sulfuryl fluoride was frequently discussed as a viable chemical alternative. The product, which has been used since 1961 to fumigate structures such as homes, museums and medical laboratories, is being developed for food uses under the Dow AgroSciences trade name ProFume gas fumigant.

Mike Drinkall, European technical specialist with Dow AgroSciences, told the conference that the company expects sulfuryl fluoride to be available for many post-harvest uses before the methyl bromide phase-out is complete.

H.J. Banks, co-chair of the Methyl Bromide Technical Options Committee, told the international conference that the change away from methyl bromide in post-harvest uses “may be minor if alternative, rapid-acting fumigants such as sulfuryl fluoride become registered on foodstuffs and available soon.”

That appears likely, as ProFume recently received an experimental use permit (EUP) from the U.S. Environmental Protection Agency for use on raisins and walnuts in California. Drinkall said the company expects to have U.S. registration for dried fruits and tree nuts, cereal grains and grain milling this year. He said European Union approval for grains and grain milling is expected in 2004. Trial fumigations conducted in both U.S. and European flour mills and fruit and nut facilities have shown excellent efficacy against key post-harvest insect pests.