For years, California growers treated strawberry fields with the fumigant methyl bromide. But that all changed when the chemical was classified as an ozone depleter and more than two dozen countries signed an international treaty called the Montreal Protocol in 1987 agreeing to phase out its use.
Growers and others who used methyl bromide were ordered to cut back their application of the chemical, with the goal of phasing it out by 2005.
However, each year the industry has applied for and received a critical-use exemption that allows reduced amounts of the chemical to be used in case a commercially feasible alternative is not available.
This year, strawberry growers can use methyl bromide on 10,000 acres, and next year, that figure will drop to 6,800 acres, said Carolyn O’Donnell, director of communications for the Watsonville-based California Strawberry Commission.
In all, there will be 40,192 acres of strawberries grown in the state this year.
Strawberry growers have reduced their use of methyl bromide by 75% since 1999, she said. When that figure will reach zero “is hard to say.”
The chemical no longer is used in areas in close proximity to places like schools, homes or nursing homes.
Meantime, the strawberry commission continues to fund ways to keep the fumigant in the soil and prevent it from leaking out.
Very impermeable films or totally impermeable films, for example, can be stretched over areas where methyl bromide is pumped into the soil.
“We’ve been looking for ways to reduce potential exposure,” O’Donnell said.
The commission also has long supported research on farming and fighting soilborne diseases without fumigants, such as by steaming the soil or through anaerobic soil disinfection, which uses a decomposing carbon source to fight diseases.
California’s Department of Pesticide Regulation is funding experiments with raised bed trough farming.
The beds look the same as any raised bed on the outside, but pulling back the plastic will reveal a trough the length of the bed that is lined with landscape cloth and filled with a medium that will not support plant disease, like coconut coir, compost, pete, rice bran or a combination of these, O’Donnell said.
The program has moved from a couple of rows in a research plot to an entire acre in a grower’s field.
But all of the proposed solutions have their challenges, she said.
Meanwhile, “We’re looking at a lot of different options,” she said. “In the end, there probably won’t be single one-size-fits all solution.”