Without methyl bromide, vegetable growers are working harder to achieve similar results from substitute fumigants.
"Methyl bromide was special," says Joe Noling, professor of nematology at the University of Florida's Citrus Research and Education Center in Lake Alfred. "Replacing it was a challenge."
Growers have several fumigant choices but the new materials require more management and are more affected by moisture, temperature and other environmental conditions, says Gary Vallad, associate professor of plant pathology at the University of Florida's Gulf Coast Research Center in Wimauma.
To get the best results from methyl bromide substitutes, "You've got to be on your game," says Stanley Culpepper, Extension agronomist in weed science at the University of Georgia in Tifton.
Culpepper helped develop Trifecta, a mixture of Telone II (1,3-dichloropropene), chloropicrin and dimethyl disulfide (DMDS). He, Vallad and Noling also are seeking ways to make the new fumigants more efficient and easier to use. Trifecta achieves that by putting three fumigants into a single application cylinder.
"Methyl bromide was idiot-proof," producing acceptable results under all conditions, says Scott DiMare, director of farm operations for DiMare Fresh Inc., in Homestead. "Now all these little mistakes show up and show up big time."
DiMare has tested most methyl bromide alternatives and has settled on Pic-Clor 60 (a mixture of 1,3-dichloropropene and chloropicrin) as his best bet so far.
"Some have better weed control, some are better with disease," he says. "The problem is nothing is consistent."
Diseases and weeds that methyl bromide once kept in check now are emerging, from persistent problems with nutsedge to increasing outbreaks of charcoal rot and Fusarium.
"Some fumigants don't even faze it," Noling says of charcoal rot.
"We're starting to see Fusarium in places we never have before," DiMare says. Crown rot, or southern blight, is another rising concern.
"The further we get away from methyl bromide, the more of these that are going to peek out,” he says.
Weeds continue as top pest
Weeds are the main ongoing problem for Georgia growers, Culpepper says.
"Usually when we have a problem, we missed nutsedge. But that was also an issue with methyl bromide," he says.
Trifecta is effective on nutsedge, but does little against annual grasses and broadleaf weeds.
"In almost all situations, growers are going to have to use herbicides," Culpepper says. That means learning how to apply herbicides in raised-bed plasticulture.