Sulfuryl fluoride - CAS No. 2699-79-8
Sulfuryl Fluoride: The Postharvest Fumigant of the Future?
USDA, October 2000.


United States Department of Agriculture (USDA), Agricultural Research Service

October 2000

Sulfuryl Fluoride: The Postharvest Fumigant of the Future?

Sulfuryl fluoride is considered by many to be the postharvest fumigant of the future, replacing the soon-to-be-eliminated methyl bromide. Under the trade name Vikane gas fumigant, it is currently registered for structural fumigations to combat wood termites and wood-boring beetles. Dow AgroSciences has begun EPA registration procedures to allow its use in postharvest situations.

Unlike methyl bromide, which is being phased out because it was determined to be an ozone depleting substance, sulfuryl fluoride is not an ozone depleter.

Dow AgroSciences is pursuing the registration of sulfuryl fluoride as a gas fumigant for postharvest use in dry fruits, tree nuts, and cereal grains. The postharvest formulation of sulfuryl fluoride will be called ProFume gas fumigant. Tolerance testing is currently under way on each of the food types, with the ultimate goal of phasing in the use of ProFume as methyl bromide is being phased out. According to Brian Schneider, Dow AgroSciences' ProFume biology development leader, this should be an accomplishable goal. "We have a jump-start since sulfuryl fluoride is already registered for structural uses," contends Schneider.

In structural fumigation, methyl bromide and sulfuryl fluoride are applied in a similar manner, and confinement procedures must be strictly adhered to for both. Schneider says sulfuryl fluoride penetrates organic substrates better than methyl bromide. "Because sulfuryl fluoride is an inorganic material, as opposed to the organic methyl bromide, it doesn't bind onto items being protected, so more of the chemical is available to get to the insects," says Schneider.

Sulfuryl fluoride is very effective against the active life stages of postharvest insects, according to ARS entomologist J. Larry Zettler of the Horticultural Crops Research Laboratory in Fresno, California. But sulfuryl fluoride requires more fumigant for egg stages than for other postembryonic stages. "But increasing exposure time or temperature may increase the chemical's effectiveness on eggs," comments Zettler.

In studies Zettler conducted with colleague Richard F. Gill, lab-reared codling moths and navel orangeworms were exposed to vacuum-chamber fumigation of a little more than an ounce of sulfuryl fluoride per cubic meter of air. The dose and length of exposure resulted in total insect kill. Codling moths and navel orangeworms are established pests of walnuts. "It has great potential as a tool in postharvest fumigation," says Zettler.

The dried fruit and nuts industry is excited about the results so far. Mike Hurley, laboratory director of the Dried Fruit and Tree Nut Association of California, feels sulfuryl fluoride will prove helpful. "Though not as effective as methyl bromide, sulfuryl fluoride is in the lead as an alternative."

Toxicity is an ever-present issue that Dow AgroSciences will address in EPA-mandated toxicity tests. According to Hurley, "sulfuryl fluoride leaves no parent compound residue on foods," meaning less chemical exposure to consumers. Fluoride residues in food commodities may be increased, however, with levels dependent on the type of commodity and fumigant dosage. Toxicity is only one feature of sulfuryl fluoride that Dow AgroSciences is committed to understanding. Dow AgroSciences is looking at ways to achieve optimal fumigation efficiency employing more efficient gas introduction procedures, improved sealing techniques, use of heat to increase susceptibility, and gas monitoring during exposure. They are also working with industry, university, and ARS researchers to help understand insect pest infestation action levels and economic thresholds to provide guidance to fumigators on treatment timing and the most economical dosages.

Pest population rebound is a significant issue for all postharvest fumigants. Several variables are involved in population rebound including gas concentration in the building, immigration, and temperature. Dow AgroSciences is looking at ways to bring about peak fumigation efficiency. Maintaining adequate gas concentration throughout the building to produce insect kill is crucial in that equation. Currently, Dow AgroSciences is also conducting modeling studies of insect population rebound after fumigation in mills and processing plants. This work complements similar research being conducted by Jim Campbell at ARS, Manhattan, Kansas, in feed mills fumigated with methyl bromide.

Though sulfuryl fluoride must undergo rigorous EPA registration procedures, its approval will provide an acceptable alternative to methyl bromide, thus filling a substantial need for postharvest fumigants.

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Last Updated: November 22, 2000

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