Researchers, growers test soil fumigants with mixed results

07/09/2012 01:54:00 PM
Tom Burfield

Florida growers have been coping with the gradual phaseout of methyl bromide for years as researchers desperately seek an alternative that will perform as well as the fumigant—or even close to it.

In Florida, methyl bromide has been used on tomatoes, peppers, eggplant, strawberries and a handful of other crops.

In 1996, methyl bromide was classified as an ozone-depleting substance by the Montreal Protocol on Substances that Deplete the Ozone Layer, and an international body called for its phaseout.

Today, use is limited to slightly more than 4 percent of the baseline year, 1991. That will drop to about 2.5 percent by 2013, says Andrew MacRae, assistant professor of weed science at the University of Florida’s Gulf Coast Research and Extension Center in Wimauma.

“It’s almost gone,” he says. Until three years ago, methyl bromide was used for tomatoes in a mixture of 67 percent methyl bromide, which fights most soilborne pests, and 33 percent chloropicrin, which is active against soilborne diseases.

Today, methyl bromide is only sold in Florida as a 50/50 combination, which disappoints growers.

“We have a lot of soilborne disease issues with tomatoes,” MacRae says. “We just don’t get the control that we used to see with 67-33.”

Methyl bromide on the way out

About the only place methyl bromide is still used is in the Miami-Dade area, where other fumigants pose a threat to the water table because of the soil type.

Methyl bromide alternatives are used elsewhere. But MacRae emphasizes that just because something may be referred to as an alternative doesn’t mean it works as well as methyl bromide.

“There is nothing in our testing or in the grower experience where we can say across the board that it is just as good as methyl bromide,” MacRae says.

For awhile, a combination of methyl iodide plus chloropicrin—sold under the trade name Midas—was used as an alternative. But the manufacturer, Arysta Life- Science, voluntarily pulled the registration in March “based on its economic viability in the U.S. marketplace,” the company said. The product was too costly to produce, MacRae surmises.

Two-way combinations

MacRae, however, has developed two-way and three-way chemical combinations that have provento be effective substitutes— depending on where they’re used.

The two-way combination consists of about 40 percent Telone and 60 percent chloropicrin.

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