- Author: Katie Harrell
Reposted from the UCANR Green Blog
Overall, 3.5 percent of the trees (based on those areas sampled during the blitzes) were found to be P. ramorum positive, a threefold drop from 2017. Yet, in San Mateo, Santa Clara and Santa Cruz counties, infection levels were estimated to be as high as 19 percent, followed by 12.7 percent in the East Bay.
"Oaks and tanoaks were infected last year and will be showing symptoms such as bleeding in the stem and canopy drying this year and in the next two years to follow. Hence, despite a reduction of SOD infection on leaves of California bay laurels and leaves of tanoaks in 2018, we can expect a sharp increase in oak and tanoak mortality in 2018, 2019 and 2020."
Notable outbreaks were detected in Alameda (El Cerrito and Oakland urban parks, San Leandro, Orinda, Moraga), Marin (Novato, Day Island, Woodacre, Sleepy Hollow, McNears Beach, China Camp State Park, north San Rafael, Tiburon Peninsula, east and west peak of Mt. Tamalpais, Marin City), Mendocino (south of Yorkville), Monterey (Carmel Valley Village, Salmon Creek Trail in southern Big Sur), Napa (east Napa city), San Mateo (Burlingame Hills, west of Emerald Hills and south of Edgewood Rd, Woodside ), Santa Clara (Los Altos Hills, Saratoga, Los Gatos, along Santa Cruz Co border), Santa Cruz (along the Santa Clara Co border, Boulder Creek), and Sonoma (near Cloverdale, east and west of Healdsburg, west of Windsor, east of Santa Rosa, west of Petaluma) counties.
Several popular destinations where P. ramorum was found positive during the 2017 Blitz were negative for the pathogen in 2018, including Golden Gate Park and the Presidio of San Francisco, the UC Berkeley campus, and Mount Diablo State Park. Samples from San Luis Obispo and Siskiyou counties were also pathogen-free as were those from the southern portion of Alameda County.
“It is encouraging that SOD has yet to be found in the forests of California's northern-most counties, San Luis Obispo County and southern Alameda County,” said Garbelotto.
“It is also encouraging to see that despite its continued presence in the state for more than 20 years, SOD infection rates drop during drier years,” he said. “However, in 2018, we identified a number of communities across several counties where significant outbreaks were detected for the first time, and the Salmon Creek find in Monterey County is the southernmost positive WUI (wildland-urban interface) tree detection ever. Until the 2018 Blitz, only stream water had been found positive in the Salmon Creek area. We encourage everyone in affected counties to look at the Blitz results online and to attend one of the fall workshops to learn how to protect their oaks from SOD.”
Citizen-science SOD Blitz workshops
SOD Blitz Workshops are being held this fall in Santa Rosa (Oct. 10), Portola Valley (Oct. 16) and Berkeley (Oct. 17). The trainings will discuss Blitz results and recommendations for protecting oaks in the WUI. Workshops are intended for the general public, tree care professionals and land managers (see www.sodblitz.org for details). Two International Society of Arboriculture continuing education units will be offered at each training. Data collected from the Blitz (both positive and negative samples) have been uploaded to the SOD Blitz map (www.sodblitz.org ) as well as to SODmap (www.SODmap.org) and to the free SODmap mobile app, which can serve as an informative management tool for people in impacted communities.
Twenty-five SOD Blitz surveys were held in 2018 in the WUI of 14 coastal California counties from the Oregon border to San Luis Obispo County and included three tribal land surveys. The 304 volunteers surveyed approximately 13,500 trees and submitted leaf samples from over 2,000 symptomatic trees to the Garbelotto lab for pathogen testing.
SOD Blitzes are a citizen science program, which train participants each spring to identify symptomatic tanoak and California bay laurel trees in the WUI and to properly collect samples in the interest of generating an informative map of P. ramorum disease symptoms over time. Samples are tested for the presence of the pathogen at UC Berkeley and results are posted electronically each fall. Now in its eleventh year, the SOD Blitz program is one of the first in the world to join researchers and volunteers in a survey for a tree disease.
SOD Blitz surveys were made possible thanks to funding from the US Forest Service State and Private Forestry, Midpeninsula Regional Open Space District, and the PG&E Foundation. The Blitzes were organized by the UC Berkeley Garbelotto lab in collaboration with the National Park Service, Presidio Trust, San Francisco Public Utilities Commission, Midpeninsula Regional Open Space District, Save Mount Diablo, Land Trust of Santa Cruz County, East Bay Regional Park District, Santa Lucia Conservancy, Sonoma State University, UC Santa Cruz Arboretum, Los Padres National Forest, City and County of San Francisco Department of Recreation and Parks, UC Berkeley Botanical Garden, and California Native Plant Society.
For information on the status of P. ramorum/SOD tree mortality in California wildlands, see the US Forest Service 2018 Aerial Detection Survey results at https://www.fs.usda.gov/detail/r5/forest-grasslandhealth/?cid=fseprd592767.
For more information on the SOD Blitzes, visit www.sodblitz.org or contact Katie Harrell at (510) 847-5482 or firstname.lastname@example.org. For more information on Sudden Oak Death and P. ramorum, visit the California Oak Mortality Task Force website at www.suddenoakdeath.org or contact Harrell.
- Author: Sarah Yang
Efforts to predict the emergence and spread of sudden oak death, an infectious tree-killing disease, have gotten a big boost from the work of grassroots volunteers.
A joint study reveals the power of citizen science in SOD Blitz, a survey project in which volunteers are trained to identify symptoms of sudden oak death. Led by Matteo Garbelotto at UC Berkeley and Ross Meentemeyer at North Carolina State University, the study was published today (Friday, May 1) in the journal Frontiers in Ecology and the Environment.
Sudden oak death is a fungus-like disease that has felled hundreds of thousands of trees in California. Crowdsourcing the survey and sampling work allowed researchers to gather information that would otherwise be too impractical and cost-prohibitive to obtain. Researchers then used the data to create a model that predicts the presence of the sudden oak death pathogen, Phytophthora ramorum, based upon such variables as rainfall and density of host trees.
Study authors compared the model based upon crowdsourced data gathered from the 2008-2013 blitzes with models using “pre-Blitz” research observations collected from 2000 to 2007. They found the SOD Blitz model to be more powerful, correctly predicting the presence of the pathogen 74 percent of the time, compared with models based on other sources of data.
“This paper shows that volunteers are as proficient as professionals in collecting data after they get some initial training,” said study principal investigator Garbelotto, an adjunct professor and cooperative extension specialist at UC Berkeley's Department of Environmental Science, Policy and Management. “The data we got from SOD Blitz resulted in the formulation of the best predictive model yet about the spread of sudden oak death in California. Additionally, we were able to identify new infestations and identify trees that needed to be removed. In one case, in Atherton, tree removal resulted in the only successful eradication of the pathogen in North America.”
The SOD Blitz model also revealed novel findings about the spread of the disease, finding that average population density and average maximum temperature were negatively correlated with the presence of the sudden oak death pathogen.
“The population density finding is important because of the debate about the role of humans in spreading sudden oak death disease,” said Garbelotto. “From this work we can say that humans are not currently spreading the disease, and that the pathogen is doing well spreading on its own.”
Beginning the Blitz
Jean Morrell, a retired biologist living on the Santa Lucia Preserve in Monterey County, learned about sudden oak death in 2007 through an on-site presentation and subsequent hike with Garbelotto that was organized for the homeowners on the preserve. The event provided the seeds for the idea of the SOD Blitz as a way to get more people – particularly other homeowners on the preserve – engaged. For Morrell, the idea kicked off a round of phone calls and personal outreach to her neighbors.
Garbelotto launched SOD Blitz the next year, in 2008, and it has since grown into one of the largest citizen science projects in the country, incorporating 21 coastal communities in California. Each spring researchers reach out to participants through news stories, radio announcements, community groups and other recruitment methods.
Participants go through mandatory, on-the-ground training by professionals to learn how to detect and sample infected trees. Training workshops last about an hour, and then volunteers are provided with symptom detection guides, a mobile mapping tool and packets for storing leaf samples.
“When it comes to predictive models, the more data the better,” said study lead author Meentemeyer, a professor of forestry and environmental resources and director of the Center for Geospatial Analytics at North Carolina State University. “This is especially true in less-studied urban ecosystems and people's backyards, where research scientists typically have little to no data. But the data need to be good, otherwise researchers are left dealing with a lot of noise. Motivated people, given a minimal amount of training, are clearly able to provide information that researchers need.”
‘People want to protect their trees'
In any one year, the return rate of participants ranges from 15 percent to as high as 40 percent, Garbelotto noted.
“From that first Blitz, we developed a core group of workers that have continued their interest and have followed up year to year,” said Morrell. “Sudden oak death is in all of our backyards, and it will have an effect on our neighborhoods. This is why we can engage people in the program. It not only allows participants to monitor their own space, but also, if they so desire, they can tromp out into the woods and do work in more remote areas. One only has to give up some ‘sweat equity' to participate, and the results are available to everyone at no cost. It's a win- win.”
Many participants are attracted to SOD Blitz by a shared love of the environment.
“I am an environmentalist, and my passion is trees. I believe they are the lungs of the Earth,” said Debbie Mendelson, who recruits SOD Blitz volunteers as a member of the Woodside Sustainability and Conservation Committee. “I think first and foremost, people want to protect their trees. Then there are folks who want to do something for the good of their community.”
Mendelson noted that SOD Blitz has also provided an opportunity to engage students in science. She has given presentations at local high schools about sudden oak death and citizen science. “I think it is a fantastic opportunity for students who have an interest in science to hear a scientist speak in an understandable and warm manner,” she said.
This year's SOD Blitz recruitment has already begun. Community meetings will be held at various locations through early June for those interested in learning more.
Once verified, data from SOD Blitz is uploaded and freely available online.
The National Science Foundation, U.S. Forest Service, Gordon and Betty Moore Foundation and PG&E Foundation helped support this work.
- Citizen Science Helps Predict Risk of Emerging Infectious Disease (Link to Frontiers in Ecology and the Environment study)
- SOD Blitz Project
- Citizen Scientists Key to Halting Sudden Oak Death (LiveScience op-ed)
- UC Berkeley a pioneer in citizen science
Will tanoak die out – is it worth saving? Tanoak (Lithocarpus densiflorus) is a California native hardwood tree common in the forest of Northern California and susceptible to Sudden Oak Death (SOD). Since tanoak is not a commercial tree should we just let it die? Tanoak has stumped manufacturers and researches alike trying to find a place for it in the market. It has many first-rate material properties but it has a reputation of being very difficult to dry without creating serious drying defects. The Fifth Sudden Oak Death Science Symposium was held in Petaluma, CA from June 19-22 to address the current knowledge of SOD and devoted a day to shed light on tanoak’s worth. The conference brought together scientists, researchers, and other experts to share information and solutions. More information on the conference presentations can be found at the conference website.
Friday’s session focused on tanoak’s importance and value. Its history and background were discussed first, summarizing its uses, advantages vs. disadvantages and economic viability. This was followed by a discussion of the efforts and studies being done to prevent tanoak trees from succumbing to SOD. The conference did an excellent job of connecting people, bringing people from different fields together to share knowledge and expertise on how to use and protect tanoak.
A presentation, titled “Tanoak as a Forest Product Recourse: Past, Present, and Future”, by John Shelly and Steve Quarles, two University of California forest products experts was presented by Steve, currently employed at the Insurance Institute for Business & Home. This presentation looked at tanoak as a potential lumber resource and compared it to more traditional hardwood species. Tanoak has a rich history as an acorn food source for Native Americans, a source of tannin—a natural chemical used to produce leather from animal hides, firewood, lumber, and pulp for paper. Compared to Northern red oak (a benchmark species), tanoak is stronger and harder, however it is more difficult to dry and exhibits greater tangential and radial shrinkage. More information is available at the UC Woody Biomass Hardwood Utilization webpage. An accumulation of experience from various researches and practitioners has led to core knowledge of best practices. These include avoiding the dark-colored core zone as it cannot be dried without defects, quarter-sawing lumber to improve dimensional stability, and using a drying schedule of air drying to 30% MC followed by a mild kiln-drying schedule. Additionally restraining the movement of wood as it dries by placing a uniform weight of about 150 lbs/ft2 on top of the lumber stack as it dries is known to be beneficial in reducing warp.
Some people are concerned that removing trees that are inflicted with the SOD tree disease pathogen will increase the risk of spreading the disease. Research reported by Shelly however, indicated that the very low risk of spreading the disease when fresh cut wood is transported to different locations disappears entirely once the wood is processed and dried. In fact, using diseased wood my even have some positive benefits. Further information is presented at: http://ucanr.org/sites/WoodyBiomass/HardwoodUtilization/SOD/ .
One such potential benefit is the presence of spalted wood –an early stage of decay—often found in SOD diseased trees. This, combined with the insect tunnels often associated with SOD infected trees creates an appealing aesthetic appearance, often called character wood. This character has the potential to set it apart from other woods. However, it was noted that spalted wood should not be used for flooring because the hardness of the wood with incipient decay is greatly reduced making it too soft for flooring. The interesting appearance of spalted wood can be very attractive in furniture, art, and craft uses. This could create a niche market for SOD-diseased tanoak that is unique, appealing to select buyers.
The participants in the tanoak session also had the opportunity to view an exhibit of a display of pictures, a slide show, and examples of tanoak lumber and finished products (e.g. flooring and furniture). The pictures and slide show depicted tanoak lumber being cut and quartered, then dried. Here the audience could see the preparation process—from forest to flooring—as well as examples of drying effects. Many people’s questions revolved around the option of using tanoak for flooring and its expected durability. Another common topic was the amount of unutilized tanoak in California forests. It is clear that there is continuing interest in finding uses for this tree. The UC experts concluded that with expansion of the market and improvements in the processing we could see a dramatic increase in the use of tanoak across California.
- Editor: Sophie Kolding
- Author: Yana Valachovic
- Author: Pamela Kan-Rice
University of California Cooperative Extension employees, who coordinate most of the sudden oak death-related research and monitoring in Northern California, got a surprise in the spring of 2010, when samples from a monitoring station near the mouth of Redwood Creek near Orick in Humboldt County 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.
Federal and state agencies, including the USDA Forest Service, CAL FIRE and the Natural Resources Conservation Service, joined forces with UC Cooperative Extension and quickly mobilized resources to control the pathogen in Redwood Valley and halt its spread to neighboring forests. Local landowners have also played a key role.
Yana Valachovic, UC Cooperative Extension advisor in Humboldt County and forestry expert, explained that she and her agency partners had been preparing for this moment.
“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,” Valachovic said.
The UCCE staff leads an extensive sudden oak death monitoring program on the North Coast, and one of their detection strategies involves "leaf-baiting" in streams. Using this technique, they “bait” Phytophthora ramorum, the non-native pathogen that causes sudden oak death, 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.
After they detected the pathogen in Redwood Creek, 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. By November 2010, the scientists had narrowed the location to Redwood Valley, where they found dead tanoaks and several other infected host plants.
Given its proximity to extensive public, private and tribal lands, the infestation in Redwood Valley was 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 5 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.
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, the USDA Forest Service and NRCS enabled the swift response in Redwood Valley. UCCE used ARRA funds, also known as federal stimulus funds, to hire four people to work on the project, lending stability to the effort.
Landowner support has been critical to the success of the project, according to Valachovic. More than 20 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.
(NRCS Forester) inspecting a treated area
“We couldn’t just stand back and let the disease roll through the forests that we manage, and the landowners understood that,” said Dan Cohoon, who works for Eureka-based Able Forestry, which manages many of the private forestlands in the watershed.
Brandon LaPorte, manager of Cookson Ranch and one of the key landowner collaborators in Redwood Valley, has supported the project from the beginning. 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, “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 project highlights the value of stream monitoring as a detection tool for SOD, but it also demonstrates 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 the 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.
The community collaboration is being honored with the Two Chiefs’ Award. The award, which is given jointly by the NRCS and the Forest Service, highlights projects from across the country each year, recognizing exemplary partners who have worked collaboratively to support conservation and forest stewardship. Valachovic will accept the award on behalf of the federal, state, tribal and private partners involved the project at an event in Davis on Wednesday, May 16.
For more information about sudden oak death disease, visit the California Oak Mortality Task Force website at www.suddenoakdeath.org.
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University of California Division of Agriculture and Natural Resources