UC Researches Alternatives to
Banned Methyl Bromide
Kan-Rice, Assistant Director, UC ANR, reported
on August 29, 2013 that California growers have used methyl bromide, a soil
fumigant, to effectively sterilize pre-planted fields since the 1960s. But now
methyl bromide is about to be phased out under an international ban.
bromide contributes to ozone depletion high in the atmosphere and was banned by
developed countries in 2005 under the Montreal Protocol, an international
treaty to protect the stratospheric ozone layer. Since then, the treaty has
allowed limited use of methyl bromide for certain crops, but many of these
exemptions are gone and the rest will end soon.
|Rootstocks for almonds and stone fruits were tested for resistance to Prunus replant disease complex near Parlier. (Photo credit: UC ANR)|
help growers find workable substitutes, University of California researchers
are part of a team working to optimize methyl bromide alternatives for western
crops including almonds, strawberries and nursery stock.
Pacific Area-Wide Pest Management Program for Integrated Methyl Bromide
Alternatives (PAW-MBA), funded by a$5 million, five-year USDA grant, is
developing and evaluating alternatives to methyl bromide for production crops
such as grapes, strawberries and tree nuts as well as nursery crops such as cut
flowers, forest trees and sweet potatoes.
goal of the program, conducted by a team of UC and U.S. Department of
Agriculture researchers, was to identify methyl bromide alternatives that were
immediately useful and economically feasible," says Greg Browne, a USDA
plant pathologist at UC Davis who coordinates the PAW-MBA program.
"Another was to foster development of nonfumigant strategies for managing
team has identified methyl bromide alternatives that are both effective and
economical for key California crops. When the best alternative is another
fumigant, the researchers found ways to use less and to cut emissions. In
addition, the researchers are developing alternatives that go beyond fumigants,
including steam sterilization and other nontoxic approaches.
film, substrates and nonfumigant soil disinfestation maintain fruit yields
growers use methyl bromide primarily to control soilborne diseases. Now, new UC
research shows that this crop can be grown without fumigants at small scales.
Three nontoxic methods — nonsoil substrates, anaerobic soil disinfestation and
steam disinfestation — produced strawberry yields as high as those in
conventionally fumigated soil.
of understanding soil, we've just been fumigating it," says Steve
Fennimore, a UC Cooperative Extension specialist in Salinas who led this team.
"Using physical tools is a different approach." Researchers will next
evaluate whether these alternative methods can be scaled up to commercial
production fields, and whether they work in different strawberry production
areas of California.
almond and stone fruit replant disease complex with less soil fumigant
and stone fruit growers need methyl bromide alternatives to control nematodes
and Prunus replant disease, a soilborne disorder that stunts new orchards and
cuts yields. UC and USDA researchers tested alternative fumigants, spot and
strip fumigation and nonfumigant methods including rotating orchards with
sudangrass and using nematode-resistant rootstock.
treatments provided adequate control of Prunus replant disease and may be very
helpful to growers needing to use less fumigant for costs savings or regulatory
restrictions,” Browne says. In addition, integrating the various treatments
tested may also help control the replant disease with less fumigant use.
1,3-D treatments test well for perennial crop nurseries, with challenges
supplies nursery stock to the state's fruit, nut and vineyard industries, as
well as more than 60 percent of the rose plants and fruit and nut trees sold
nationwide. This perennial nursery stock must be completely nematode-free, and
growers use methyl bromide primarily to control these tiny soilborne worms.
alternative fumigants such as 1,3-dichloropropene (1,3-D) don't work as well in
fine soils. "We asked how we could make them work better," says Brad
Hanson, a UC Cooperative Extension specialist in the Department of Plant
Sciences at UC Davis. The researchers showed that 1,3-D controlled nematodes in
fine soil when they tilled it deeper, injected the fumigant deeper and used
tarps that kept more of the fumigant in the soil.
emission reductions with TIF warrant regulatory changes
are regulated partly because they help make smog. Totally impermeable film
(TIF) can help keep fumigants in the soil and out of the air. New UC research
shows that fumigant emissions can drop 64 percent when fields are tarped with
TIF for twice as long as usual (10 days instead of 5).
now working on safe use," says Suduan Gao, a USDA soil scientist in
Parlier who led the team. "The goal is to keep the fumigant under the tarp
long enough that there won't be a surge in emissions when it's cut open."
This work gives regulatory agencies a new way to let growers keep using enough
fumigant to control pests and diseases while minimizing the smog-forming
Labels: Alternatives to Banned Methyl Bromide, Brad Hanson, Greg Browne, Pacific Area-Wide, Pamela Kan-Rice, PAW-MBA, Prunus, Steve Fennimore, sudangrass, Suduan Gao, UC ANR