TIFTON, Ga. – Since the 1940s, methyl bromide has served farmers well as a stunningly lethal fumigant, killing off pests such as fungi, weeds, insects and rodents.
But amid requirements that farmers stop using it, University of Georgia students are joining an international effort to find an earth-friendly alternative.
Alex Cisnos, a plant pathologist, and other researchers at the university's Coastal Plain Experiment Station in south Georgia have been testing an alternative fumigant, metam-sodium, in a one-quarter acre test plot of vegetables, including tomatoes and squash.
The move to phase out the use of methyl bromide is a result of the United Nations' 1992 Montreal Protocol, which identified the pesticide as one of many chemicals that damages the stratosphere's layer of ozone.
Humans would be at greater risk of skin cancer and other health problems if the ozone layer continues to be damaged.
The deadline for the United States and 32 other industrialized countries to stop using methyl bromide was Jan. 1, 2005, but the U.N. agreed to allow "critical exemptions" on a few crops. Methyl bromide is still used for strawberries and tomatoes, crops for which there is no effective alternative.
The alternatives that are being developed may involve using a "cocktail" of chemicals that are more expensive, more costly to apply, less efficient and possibly toxic for days or weeks, Cisnos said.
Farmers liked methyl bromide because it was cheap, efficient and it dissipated in a few days, allowing them to return quickly to their fields, he said.
"It kills basically everything," Csinos said.
His research is focused specifically on the effectiveness of metam-sodium. Some farmers may find they need to use additional chemicals to kill pests, such as some weeds, that might survive the metam-sodium treatment, he said.
The work at the University of Georgia, which is being funded by the federal Agricultural Research Service, is taking place in a plot full of rows of crops covered with plastic so that scientists can control growing conditions. Like other growers in the area, scientists fertilize and water the crops through plastic tubes buried in the soil.
But in this plot, sprouting from the rows are small clear, plastic tubes for collecting gas samples and larger black tubes attached to gas cylinders for pumping the test fumigant under the plastic.
Buried in the ground are 24 electronic sensors to measure water distribution in the bed. Periodically, the researchers place bags loaded with micro-organisms under the plastic through slits to check the fumigant's distribution and killing power.
"We're trying to determine how well it distributes and how well it kills specific pests," Csinos said. "That is the scientific unknown."
Gary Obenauf, manager of Methyl Bromide Alternatives Outreach, said Csinos and his team of researchers are among a network of scientists around the world searching for alternatives.
The use of alternative chemicals, plus cuts in the production and importation of methyl bromide, have already reduced the agricultural use of the fumigant by more than 70 percent since 1991, Obenauf said.
"We're making progress," said Obenauf, a farm consultant in Fresno, Calif. "But unfortunately, we still have gaps. We still have places where we don't have viable alternatives. Those are the areas where we are really concentrating the research. ... Without tremendous amounts of money, there is no quick fix, so it's just taking time to go through this."