- Author: Kara Manke
Reposted from the UC Berkeley News
Two tanoak trees in Del Norte county tested positive for the pathogen known to cause sudden oak death, reports a team of collaborators from Cal Fire, UC Cooperative Extension and SOD Blitz. (UC Berkeley photo courtesy Matteo Garbelotto)
A team of collaborators including the citizen science project SOD Blitz have detected the first cases of the infectious tree-killing pathogen Phytophthora ramorum in California's Del Norte county.
The pathogen, a fungus-like water mold that causes sudden oak death, has ravaged millions of native oaks and tanoaks along California's central and northern coasts since it was first introduced in the United States in the late-1980s.
The discovery in Del Norte marks the first time that sudden oak death has been found in a new county since the its emergence in nearby Trinity county in 2014, and brings the total number of affected California counties to 16.
“Now every California coastal county between Oregon's Curry County and the very southern border of Monterey County are infested, although the extent and distribution of infested areas within each county is extremely variable” said Matteo Garbelotto, an adjunct professor of environmental science, policy and management at the University of California, Berkeley, and founder and director of the SOD Blitz program.
“If the infestation in Del Norte were to expand, not only it would affect local resources, but it would also provide a bridge connecting the genetically distinct Oregon and California infestations, possibly further facilitating the adaptation of the pathogen to West Coast coastal forests,” said Garbelotto, who also serves as cooperative extension specialist for University of California Agriculture and Natural Resources. “It's a good thing that we detected it, because the sooner we know, the more options are available to minimize the impact of the disease.”
Each year, the University of California, Berkeley-led SOD Blitz project has employed volunteers from around the state to scour their local forests for signs of new outbreaks of the pathogen. Del Norte County has been monitored for these signs since 2004 by collaborators from UC Cooperative Extension, UC Berkeley, UC Davis, and Cal Fire. This year, the SOD Blitz brought additional sampling infrastructure and diagnostic expertise to the effort.
The two infected trees are located in Jedediah State Park about five miles east of Crescent City. (Photo by Yana Valachovic)
Hundreds of tree samples from uninfested San Luis Obispo county were also tested as part of this year's SOD Blitzes, but no cases were found.
The strain identified in Del Norte is the one called NA1, which is commonly found in California, rather than the emergent and potentially deadlier EU1 strain common in Europe and recently detected in Oregon.
The new finding has been reported to the California Department of Food and Agriculture (CDFA), and has no regulatory implications until the results are officially confirmed by the CDFA.
A new threat in Del Norte
The two infected trees in Del Norte county are located in Jedediah State Park about five miles east of Crescent City, reports Chris Lee, a forest pathologist with Cal Fire who organized this year's SOD Blitzes in Humboldt and Del Norte counties.
“The tanoak trees are located among old-growth redwoods, pretty far from the existing infestations we know of in Oregon and in northern Humboldt County,” Lee said. “Fortunately, past experiences indicate that redwoods suffer only minor damage from this pathogen. Little to almost no mortality of other tanoaks can be observed in the immediate surroundings at this site so far.”
The researchers also conducted follow-up testing on surrounding trees in the area but no additional cases of the pathogen were found.
“We have been monitoring this county for years and I had been hopeful that it would be spared from the disease,” said Yana Valachovic, forest advisor and county director for the UC. Cooperative Extension office in Del Norte and Humboldt Counties and co-sponsor of the Humboldt-Del Norte SOD Blitz. “A round of secondary sampling in nearby trees did not yield the pathogen making it difficult to speculate how the disease may have arrived and the extent of the infestation. Over the coming months we will be working with the landowners and managers of the region to help them assess the situation.”
Two volunteers collect samples during an SOD blitz. (UC Berkeley photo by Doug Schmidt, Garbelotto Laboratory)
More than a decade of Blitzes
Since Garbelotto launched the SOD Blitzes in 2007, thousands of volunteers have combed through California's coastal forests in search of signs of Phytophthora ramorum, the pathogen, which causes oozing cankers, browning leaves, and eventual death in infected oak and tanoak trees.
“The Blitzes started because we were and still are facing the necessity of precisely defining the extent of the SOD infestation over a gigantic range, and it was basically impossible for us to hire enough people to actually survey they entire coast of California,” Garbelotto said.
For each Blitz, Garbelotto partners with local organizations to recruit and organize volunteers. After a short training session, participants, many of whom are private landowners, survey a designated area for hints of the pathogen, which is often spread through infected bay laurel leaves and tanoak twigs.
Suspicious-looking leaves and twigs, along with details about the location, are sent to Garbelotto's lab at UC Berkeley, where they undergo a rigorous analysis and DNA testing to confirm the presence of the pathogen.
Every fall, their findings are combined with data from researchers as well as state and federal government agencies and made publicly available on the web (www.SODmap.org).
Every year, the results of the SOD Blitzes are compiled data from state and federal government agencies and made publicly available on the web. Green icons identify the locations of tree samples that tested negative for the sudden oak death pathogen, and red icons indicate trees that that tested positive for the pathogen. (UC Berkeley image by Doug Schmidt, Garbelotto Laboratory)
“Everybody who attends the SOD Blitzes is great, they are really interested and want to protect their trees,” said Kim Corella, a forest pest specialist at CalFire who has been organizing the SOD Blitzes in San Luis Obispo county since 2013.
In 2019, there were 22 local SOD Blitzes ranging from San Luis Obispo county in the south to Del Norte in the north. A total of 455 volunteers participated, 16227 trees were surveyed and 9000 leaves from 1732 trees were sampled and tested at UC Berkeley.
Though the SOD Blitzes have identified a number of new outbreaks, this is the first time that the project has uncovered infections in a new county.
“Our citizen science program run by UC Berkeley has been successful thanks to many collaborators, including UC Cooperative Extension, Cal Fire, the California Native Plant Society and the San Francisco Public Utilities Commission, just to name a few,” Garbelotto said. “Our project is providing key research findings to protect California Natural resources, highlighting the relevance Citizen Science has in the modern world.”
The project is supported by the US Forest Service, State and Private Forestry as well as the National Science Foundation, the Gordon and Betty Moore Foundation and the Pg&E Foundation.
- 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.
Video of Dr. Matteo Garbelloto describing the three steps to managing sudden oak death.
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 kmharrell@ucdavis.edu. 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
Reprinted from the UC Berkeley News Center.
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.
RELATED INFORMATION
- 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
