Methyl bromide phased out, berry-growers wary of new alt, methyl iodideMelissae Fellet, The Californian
Ruby-red strawberries are the jewels of Monterey County agriculture. But an international treaty that eliminates a commonly used soil fumigant threatens to reduce the number of strawberries harvested here.
The fumigant is methyl bromide, a highly effective chemical for killing pests that was banned worldwide in 2005 because it destroys the ozone layer, Earth's shield against harmful ultraviolet rays.
The dilemma for California strawberry growers is that finding a chemical as effective as methyl bromide remains elusive a fact that worries many local farmers. Growing strawberries organically yields healthier fruit, but rotating crops on organic fields means fewer berries are planted each season.
"It's a new world for strawberries," said Mark Bolda, farm adviser for strawberries and caneberries in Monterey, Santa Cruz and San Benito counties at the University of California Cooperative Extension.
Last year, strawberries surpassed lettuce as the highest grossing crop in Monterey County, bringing in $756 million in revenue. The farms around Salinas and Watsonville produced 41 percent of the state's berry crop this year, according to the California Strawberry Commission.
Shimmering plastic tarps stretched neatly over straight rows cover fields throughout the Salinas and the Pajaro valleys before fumigation. Methyl bromide kills fungi, insects, nematodes and weed seeds as it spreads through the soil as a gas. The tarps trap the fumigant in the soil, preventing it from evaporating into the air.
Critical use exemptions allow certain countries to continue using methyl bromide because of the lack of effective alternatives. These exemptions are due to end worldwide by 2015 in accordance with the Montreal Protocol, an international treaty that restricts the use of ozone-depleting chemicals.
One alternative to this fumigant is methyl iodide, a chemical cousin of methyl bromide that does not damage the ozone layer.
The California Department of Pesticide Regulation on Wednesday approved the use of methyl iodide, and the department expects the fumigant to be available later this month once emergency regulations are in place. It will be sold by Tokyo-based Arysta LifeScience Corp. under the brand name Midas as a mixture with chloropicrin, another fumigant.
Anti-pesticide groups plan to fight the registration with a lawsuit, citing concerns that the chemical is too toxic to be handled safely. Methyl iodide is listed as a human carcinogen in California. Methyl bromide, on the other hand, is listed as a developmental toxicant, meaning it can harm a developing fetus and cause birth defects.
To ensure the safety of workers and the public, state regulators placed extra restrictions on methyl iodide applications, including extending buffer zones around treated fields, reducing the number of acres that can be treated at one time and prohibiting nighttime applications.
Because of these restrictions, farmers "might not be able to use it in every situation," said Bob Roach, Monterey County's assistant agricultural commissioner. "But it gives farmers one more option."
Transitioning to other fumigants
Watsonville strawberry grower Miguel Ramos participated in experimental field trials for methyl iodide from 2006 to 2008. But now he won't be able to use the fumigant on his fields because there's a bus stop within the borders of the extended buffer zone.
There's "some uncertainty right now" about what the future will bring to his farms, Ramos said.
Ramos, who has grown berries for almost 30 years, said it took two seasons to learn how to evenly apply a small amount of methyl iodide to a large field.
"Once we did that, we noticed that it was very good for controlling disease," he said.
Roach said Monterey County farmers have also been experimenting with telone and chloropicrin. But, he said, the chemicals have limited effectiveness.
"They seem to do good for two years. Then farmers have trouble with pathogens," said Karen Stahlman, the county's chief deputy agricultural commissioner. If they can, farmers then treat their fields with methyl bromide to clean them up, she said.
Even though the methyl bromide ban is still four years away, Monterey County farmers are starting to feel some sticker shock. As methyl bromide supplies become limited, Roach said, the costs are increasing.
And switching to methyl iodide might not help a farmer's pocketbook. Arysta says the cost of Midas will be comparable to methyl bromide. And that, Ramos said, is "pretty pricey."
Potential population exposure
Farmers use the same equipment to treat fields with either methyl bromide or methyl iodide. The liquid chemical is either injected into the soil or fed into tubes buried in the soil. It vaporizes and enters the soil as a gas.
Although methyl iodide is not as prone to drift as methyl bromide, tarps can rip, tear and blow away, said Paul Towers, state director of Pesticide Watch Education Fund.
"There has never been a tarp that is 100 percent effective at protecting neighboring communities," Towers said.
Both methyl iodide and methyl bromide are dangerous chemicals. The U.S. Environmental Protection Agency lists methyl bromide as a potential cancer-causing chemical in mice. Although methyl iodide is more toxic, lack of scientific evidence has kept the EPA from classifying it as a carcinogen.
With the required health safeguards in place, "methyl iodide can be used without risks to the public," said Mary-Ann Warmerdam, director of the Department of Pesticide Regulation.
Like methyl bromide, methyl iodide does not affect the berries themselves because the chemical is only used before planting. Farmers usually put strawberry transplants in the ground one to four weeks after fumigation, said farm adviser Bolda. All methyl iodide must be gone before the new crop is planted; otherwise, the young plants would die.
Threat to groundwater?
After methyl iodide kills soil pathogens, it leaves behind iodide, an ion that dissolves easily in water and is linked to thyroid problems. So environmentalists, toxicologists and scientists fear groundwater contamination could pose a risk to the general population.
Recent groundwater monitoring in Florida, where methyl iodide has been in use since 2008, showed higher levels of iodide than deemed safe, Towers said. But Florida agricultural officials say they're reluctant to draw conclusions from some of the first data collected during the study.
Iodide levels were high before and after methyl iodide was applied to a test field, said Dennis Howard, chief of the Bureau of Pesticides in Florida. The excess iodide could have come from other human sources or could be naturally occurring, he said. The test field was treated in December 2008 and again in January of this year, when the water quality study began. It's expected to last two years, Howard said.
Watchdog groups, however, say the Florida test could be a warning sign for California. Because Florida has a higher water table than the Golden State, it could be some time before the chemical shows up in California water, Towers contended.
California regulators disagree about the threat to groundwater. In a statement last June, Warmerdam, the California pesticide regulator, said independent tests by her department and the federal EPA concluded that "methyl iodide is unlikely to affect water quality."
Growing strawberries organically eliminates chemical pesticides, but farmers often sacrifice higher yields. Recent research has shown, however, that organic farmers have something to gain higher-quality fruit and healthier soil.
A team of researchers led by John Reganold, a professor at Washington State University, compared strawberries grown on conventional and organic strawberry farms around Watsonville in 2004 and 2005. The results, published in September, showed that strawberries grown organically had higher levels of antioxidants and polyphenols, compounds linked to reducing cancer risk, than did fruit from the conventional farms. Also, soil from the organic farms had higher levels of beneficial microbes.
About 8 percent of the 2010 strawberry acreage around Watsonville and Salinas is now organic fields, according to a report from the California Strawberry Commission.
Organic farmers control soil pests and pathogens with multi-year crop rotations. Broccoli, for example, contains natural fungus-killing compounds, and legumes help build a healthy community of soil microbes.
But this approach takes time. Farmers cannot plant strawberries as consistently, said Gary Peterson, deputy director at the Agriculture and Land-Based Training Association, a Salinas organization that trains farmers in organic practices.
Looking to the future
Scientists have been searching for chemical alternatives to methyl bromide for about 20 years, but progress is slow, Bolda said, because it's hard to top the effectiveness of methyl bromide mixed with chloropicrin.
The California Strawberry Commission is investing in research aimed at finding long-term solutions, said Carolyn O'Donnell, communications director of the commission. She said every year brings a new discovery, such as a new plant variety that is more disease-resistant or a new and effective crop rotation.
Scientists at the United States Department of Agriculture research station in Salinas and the cooperative extension in Monterey are also working to find alternatives.
The farming landscape after methyl bromide is undefined. Yet farmers are still fighting soil pathogens that can live in the soil for years. Without effective fumigants, less land will be clean enough to plant strawberries.
"I believe the very best areas for growing strawberries will be going out of production," said berry grower Ramos.
Researchers agree, but they still hold out hope.
"Yields will go down and production will fall," Bolda said, "but it's not Armageddon."