Santa Cruz Good Times

Tuesday
Sep 01st
Text size
  • Increase font size
  • Default font size
  • Decrease font size

Growing Berries Without Bromide

news2Researchers test a new alternative to a controversial chemical

The scarecrows perched in Santa Cruz strawberry fields do little to scare away the birds, much less the insects and fungi harbored in the soil. Everything likes to eat strawberries, which makes growing them a risky business.

This predicament led UC Santa Cruz professor Carol Shennan to take an unconventional approach to pest management. Nine years ago, the fatal plant disease Verticillium wilt was wiping out strawberry plants at the university farm. Chemicals hardly phase the pathogen, and Shennan saw little improvement with crop rotation, which is typically used to treat infested fields. A visiting plant pathologist from the Netherlands recommended a little-known organic technique called anaerobic soil disinfestation, and, with so few other options, Shennan decided to give it a try. 

“After the first treatment we almost entirely eliminated Verticillium from the soil,” says Shennan. The number of disease spores dropped from 20 per gram of soil to zero or one—a success story that earned Shennan and her collaborators a $725,000 grant from the U.S. Department of Agriculture in 2007. 

Shennan is currently compiling nearly a decade of results comparing anaerobic soil disinfestation to chemical fumigation. The results, which will be submitted for publication this summer, show that after disinfestation, the number of Verticillium disease spores consistently drops by 80 to 100 percent. “This is similar to the levels we have achieved with fumigation,” says Shennan.

Kill-all fumigants like methyl bromide have been a staple of the local berry industry for decades. Twenty years ago most California strawberry crops were treated with methyl bromide, and after the ozone-depleting chemical was banned by the Montreal Protocol, the United States lagged behind other nations in the phase-out process.  This year, with the Environmental Protection Agency starting to crack down, only 8,000 acres of California berries will be treated with methyl bromide, and next year critical use exemptions will permit only 5,000 acres.

“Farmers have tried other fumigants, but there aren’t a lot of good options,” says Carolyn O’Donnell, of the California Strawberry Commission. Methyl iodide could have been used on berry farms, but it was pulled from the market last year after national environmental campaigns raised concerns over toxicity. Many of the few remaining fumigants have been criticized for increasing plant disease. 

“The early adopters of alternative fumigants have seen the emergence of new varieties of soil disease,” says O’Donnell. Pathogens like Macrophomina and Fusarium were not a problem in strawberry fields when methyl bromide was used, but after farmers changed their fumigation practices, the diseases were identified in several fields in Santa Barbara, Ventura and Orange counties.  Chemical fumigants are criticized for wiping out good bacteria as well as disease organisms. After treatment, many microbial communities are severely diminished. This eliminates the competition for invading pathogens, and kills the beneficial microbes that help fight plant diseases.

news2-2Determining best practices for growing strawberries is a vital question for California, where there are more than 40,000 acres of strawberries. Half of the state’s crop is grown in Watsonville and Salinas, where the average berry farm spans 80 acres.  In Santa Cruz County’s agriculture-driven economy, the sweet red berries remain the highest valued crop, raking in more than $198 million in 2011.

The problem has turned the spotlight to fumigant-free alternatives like anaerobic soil disinfestation. While disease organisms decline after treatment, the total number of soil bacteria increase. Disinfestation appears to alter microbial communities, but it likely does not kill as many organisms. Disinfestation is also less toxic to humans than chemical fumigation as the active ingredients are inert. 

As part of the treatment, carbon sources like rice bran, molasses and grape skins are mixed into the soil. A tarp is placed over the field, and drip irrigation is used to saturate the planting beds. This triggers the growth of anaerobic bacteria. “We don’t know the exact mechanism by which this kills pathogens, but it likely involves the organic acids produced by anaerobic bacteria,” says Shennan.

While disinfestation uses more water than fumigation, the technique is primarily criticized for being new—no one knows which pathogens the method kills, or whether treatment will work on a large, industrial farm.

So far, treatment has been limited to much smaller plots. This growing season, Watsonville-based Farm Fuel Inc. treated more than 130 acres in Santa Cruz and Monterey with the disinfestation method. The largest treated plot was 25 acres, but Farm Fuel Inc. CEO Stefanie Bourcier says she isn’t afraid to treat bigger sites. “We started offering treatments as a commercial service in 2011, and each year we have done larger and larger plots,” she says.

Bourcier looked into the technique after Fusarium wilt infected perennial herbs at an affiliated farm. She and her colleagues treated two sites with anaerobic soil disinfestation, and results were promising. “The plants did really well after treatment, and we didn’t see big die-offs,” says Bourcier. “However the neighboring block of plants was not treated, and it had significant disease.” 

According to Bourcier, the treatment is also cost effective. It currently costs $3,900 per acre to treat strawberries with methyl bromide, while anaerobic soil disinfestation totals $2,700 an acre.  While other fumigants are a little cheaper, disinfestation will enter the market at the middle-range price.

“This is very important in the berry industry because you have to invest a lot of money before you can make money,” says Shennan.  A farmer can earn $50,000 an acre growing berries, but they will likely spend $25,000 to plant.

This is why the California Strawberry Commission has contributed $3 million to fumigant-free programs over the last five years; a third of this has gone to anaerobic soil disinfestation research. 

“There is no silver bullet, and we aren’t going to find a replacement for methyl bromide overnight,” says O’Donnell. “But anaerobic soil disinfestation shows a lot of promise, and it’s one of a few techniques that might really help.”

Comments (1)Add Comment
Paralegal
written by Abby , May 22, 2013
Verticillium responds to fumigation, but not always. I'm glad there is an alternative in the works.

Write comment
smaller | bigger

busy
 

Share this on your social networks

Bookmark and Share

Share this

Bookmark and Share

 

The Meaning of ‘LIFE’

With a new documentary film about his work, and huge exhibits on both coasts, acclaimed Santa Cruz nature photographer Frans Lanting is having a landmark year. But his crusade for conservation doesn’t leave much time for looking back

 

Seasons of Opportunity

Everything in our world has a specific time (a season) in which to accomplish a specific work—a “season” that begins (opportunity) and ends (time’s up). I can feel the season is changing. The leaves turning colors, the air cooler, sunbeams casting shadows in different places. It feels like a seasonal change has begun in the northern hemisphere. Christmas is in four months, and 2015 is swiftly speeding by. Soon it will be autumn and time for the many Festivals of Light. Each season offers new opportunities. Then the season ends and new seasons take its place. Humanity, too, is given “seasons” of opportunity. We are in one of those opportunities now, to bring something new (Uranus) into our world, especially in the United States. Times of opportunity can be seen in the astrology chart. In the U.S. chart, Uranus (change) joins Chiron (wound/healing). This symbolizes a need to heal the wounds of humanity. Uranus offers new archetypes, new ways of doing things. The Uranus/Chiron (Aries/Pisces) message is, “The people of the U.S. are suffering. New actions are needed to bring healing and well-being to humanity. So the U.S. can fulfill its spiritual task of standing within the light and leading humanity within and toward the light.” Thursday, Aquarius Moon, Mercury enters Libra. The message, “To bring forth the new order in the world, begin with acts of Goodwill.” Goodwill produces right relations with everyone and everything. The result is a world of progressive well-being and peacefulness (which is neither passive nor the opposite of war). Saturday is the full moon, the solar light of Virgo streaming into the Earth. Our waiting now begins, for the birth of new light at winter solstice. The mother (hiding the light of the soul, the holy child), identifying the feminine principle, says, “I am the mother and the child. I, God (Father), I Matter (Mother), We are One.”

 

The New Tech Nexus

Community leaders in science and technology unite to form web-based networking program

 

Film, Times & Events: Week of August 28

Santa Cruz area movie theaters >
Sign up for Good Times weekly newsletter
Get the latest news, events

RSS Feed Burner

 Subscribe in a reader

Latest Comments

 

Land of Plenty

Farm to Fork benefit dinner for UCSC’s Agroecology Center, plus a zippy salsa from Teresa’s Salsa that loves every food it meets

 

If you knew you had one week to live, what would you do?

Make peace with myself, which would allow me to be at peace with others. Diane Fisher, Santa Cruz, Network Engineer

 

Comanche Cellars

Michael Simons, owner and winemaker of Comanche Cellars, once had a trusted steed called Comanche, which was part of his paper route and his rodeo circuit, from the tender age of 10. In memory of this beautiful horse, he named his winery Comanche, and Comanche’s shoes grace the label of each handcrafted bottle.

 

Cantine Winepub

Aptos wine and tapas spot keeps it casual