UCCE Humboldt - Del Norte Counties
University of California
UCCE Humboldt - Del Norte Counties

Redwood Valley Adaptive Management Project


HUMBOLDT COUNTY—When you think of bait, you probably envision worms or flies, not rhododendron leaves in mesh bags. But scientists have found a way to “bait” Phytophthora ramorum, the non-native pathogen that causes sudden oak death (SOD), by placing susceptible leaves in strategic locations in North Coast streams. If the leaf baits become infected with SOD, the scientists know that the pathogen is present in the watershed without having to comb the landscape for symptoms.

University of California Cooperative Extension (UCCE) employees, who coordinate most of the SOD-related research and monitoring in northern California, got a surprise in the spring of 2010, when leaves from a monitoring station near the mouth of Redwood Creek by Orick tested positive for the pathogen. This meant that trees were infected somewhere in the 200,000 acre watershed – more than 50 miles from the nearest known infestation, and farther north than the pathogen had ever been detected in California.

UCCE acted quickly to pinpoint the source of the waterborne spores, scouring the watershed for the very inconspicuous symptoms of SOD with the help and permission of public and private landowners and managers. By November 2010, they had narrowed the location to Redwood Valley, where they found dead tanoaks and several other infected hosts.

Given its proximity to extensive public, private, and tribal lands, the new infestation in Redwood Valley is a serious concern. The disease, which was discovered in the Bay Area in the mid-1990s, is found in 14 coastal counties in California, from Monterey to Humboldt, and has infested 10 percent of the at-risk areas in the state. P. ramorum thrives in the coastal climate, and has killed over a million tanoaks and true oaks over the past 15 years.

It’s still not clear how the pathogen got to Redwood Valley, but it could threaten the dense tanoak forests of the surrounding area, resulting in widespread tree mortality and increased fire hazard. As Bruce Moltzan, Plant Pathologist with the USDA Forest Service in Washington D.C., explained, “the control of this new infestation is a top priority for the agency’s Forest Health Protection Program, both locally and nationally.”

In spring 2011, federal and state agencies, including the USDA Forest Service, Cal Fire, and the Natural Resources Conservation Service (NRCS), joined forces with UCCE and quickly mobilized resources to control the pathogen in Redwood Valley and halt its spread to neighboring forests. Yana Valachovic, Forest Advisor for UCCE, explained that this was the moment everyone had been preparing for. “We’ve been closely monitoring the disease for years and anticipating a scenario like Redwood Valley, so we were ready to take action and respond quickly.”

Much of the on-the-ground effort has been completed by contractors and Cal Fire handcrews, who have created 100-meter buffers around infected trees by removing California bay laurel (pepperwood) and tanoak, the two hosts that most readily support P. ramorum spore production and spread. Infected plant material has been trucked offsite and donated to the nearby DG Fairhaven Power Company, piled and burned, or lopped and scattered onsite.

Funding from the American Recovery and Reinvestment Act (ARRA), the USDA Forest Service, and the NRCS has been critical to the swift response in Redwood Valley. ARRA funds have supported UCCE staff throughout the project, lending stability and guidance to the effort.

Landowner support has also been critical to the success of the project. Landowners in the valley have allowed monitoring and treatment activities on their properties, recognizing that their cooperation may keep the disease from spreading to other areas. Dan Cohoon works for Able Forestry, a company in Eureka that manages many of the private forestlands in the watershed; his connections with landowners made him a critical partner in the project. “We couldn’t just stand back and let the disease roll through the forests that we manage, and the landowners understood that,” he said.

Brandon LaPorte, manager of Cookson Ranch and one of the key landowner collaborators in Redwood Valley, has supported the project from the beginning. As LaPorte explained, “We’ve learned a lot about the disease through this project, and we certainly don’t want it getting worse here on the ranch or spreading beyond the valley.”

The first phase of treatment is currently wrapping up, and UCCE is beginning to monitor project efficacy and watch for spread of the pathogen beyond project boundaries. The Yurok and Hoopa tribes will be paying close attention to this effort, as they are only a ridge away from the infestation. Ron Reed, a Yurok tribal forester, commented that “Oaks are an important part of our culture and history, and we will do what we can to keep sudden oak death out of our forests.”

The Redwood Valley treatment project involved more than 20 private landowners, funding from 4 different sources, over 180 days of CAL FIRE crew time, thousands of laboratory samples, and the determination and collaboration of many individuals and organizations. The project demonstrates the value of stream monitoring as a detection tool for SOD, and the ability of agencies and landowners to collaborate swiftly and effectively to protect the region’s forest resources. Maybe most important – regardless of the future course that sudden oak death takes in the North Coast – is what this project shows about the ability of proactive communities concerned about the health of their landscapes to come together, attract the support of state and national authorities, and work to make things better.

For more information on the project or on sudden oak death monitoring in Humboldt County, contact Yana Valachovic at yvala@ucdavis.edu or (707) 445-7351. For more information on the disease, visit the California Oak Mortality Task Force website at www.suddenoakdeath.org.  

One of the Redwood Valley project areas before and after treatment. 



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