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Posts Tagged: Matteo Garbelotto

Phytophthora invasions linked to ecological restorations

Dead and dying coffeeberry (Frangula californica) shrubs are clearly visible in a failing restoration in a coastal scrub site in San Mateo County, dominated by shrubs with occasional small groups of trees. Phytophthora crassamura and P. megasperma were both isolated directly from symptomatic tissue and from the rhizosphere (i.e. soil and fine roots) of diseased plants. Photo by Laura Sims.

Biological invasions are one of the three main causes for biodiversity loss globally, together with urbanization and climate change. Not unlike animals and plants, microbes can become invasive in non-native ecosystems. Some microbial invasions can lead to novel plant diseases with direct and detrimental effects on terrestrial ecosystems. The plant trade, both international and domestic, is thought to be a major pathway for the introduction and spread of exotic plant pathogenic microbes. Some introductions are accidental, but systematic introductions are significantly more detrimental for the integrity of natural ecosystems.

In a new study published in the journal Biological Invasions,  Matteo Garbelotto, a Cooperative Extension specialist and adjunct professor in the Department of Environmental Science, Policy, and Management (ESPM), investigates whether multiple species of the plant killer genus Phytophthora—which includes the infamous Sudden Oak Death pathogen—could have been brought into natural habitats during restoration projects.  Through one of the first controlled studies on the subject, Garbelotto and Laura Sims, a study co-author at Louisiana Tech University, found that plants used in restoration projects often were infected and killed by one or multiple Phytophthora species. 

From surveys of control undisturbed sites near failing restorations, as well as plant production facilities providing the plant stock used in these restorations, the authors were able to conclude that these pathogens were not already present in restored habitats. Rather, they were introduced through plants or soil contaminated in the plant production facilities themselves.

The researchers tested six plant species for the presence of Phytophthora in 14 study sites across three San Francisco Bay Area counties. A statistical analysis found significantly higher percentages of Phytophthora occurrences on plants and soil in restoration sites and adjoining disturbed sites than in control undisturbed sites, where no Phytophthoras were isolated. The researchers found greater rates of disease symptoms and plant death, as well as a lack of regeneration, where Phytophthoras were present. 

“All other studies so far simply reported the presence of these soil borne pathogens in restorations, but without any solid experimental evidence that they were introduced through the restoration efforts,” says Garbelotto. “In this light, the paper is transformative. The fact that Phytophthoras were found in all restoration sites studied and on multiple plant hosts shows these are not isolated occurrences, but that habitat restoration projects in the near past have repeatedly and systematically resulted in the introduction of these aggressive pathogens.” He adds that the absence of these pathogens in neighboring unrestored and undisturbed sites suggests that at least some of the species found may be exotic, and particularly deadly, for plant hosts that have not previously encountered them. 

Clockwise from upper left, healthy plant, Diplacus aurantiacus plants infected with Phytophthora and canker from which Phytophthora megasperma was isolated. Photos by Laura Sims

“The second key result of our study was the finding that these pathogens are spreading invasively through infested soil and water well outside the borders of restorations”, says co-author Laura Sims. “This indicates that extremely costly restoration projects, rather than restoring the integrity of the ecosystem, may further deteriorate its health, by introducing invasive plant pathogens. Historically, man has never been able to eradicate these pathogens, once they have established in natural habitats. We have shown such establishment is happening in natural habitats near the restoration sites we studied”

The study was partially conducted in the Presidio of San Francisco, a national park site. “Plantings and landscape restorations are a big part of what we do in the Presidio,” says Christa Conforti, biologist and Integrated Pest Management Specialist with the Presidio Trust. “This study shows that restorations have unwittingly introduced plant pathogens that cannot feasibly be eradicated, and that repeated introductions are particularly dangerous. This evidence justifies investing our resources to ensure we take significant precautions when using nursery-grown plants in our landscapes, to help us meet our mission of protecting biodiversity and native ecosystems into the future.”

As a faculty member in ESPM, Garbelotto researches exotic forest diseases, fungal ecology, biodiversity, geonomics, wood decay and tree stability, and the management of forest diseases. He also runs a citizen science initiative in California to find and combat the exotic disease sudden oak death (SOD), known to have decimated native oak and tanoak populations. Garbelotto was featured in Breakthroughs magazine in 2019. The lab he runs also provides diagnostic services and forensic evidence on factors leading to tree failure.

The full study, titled “Phytophthora species repeatedly introduced in Northern California through restoration projects can spread into adjacent sites,” can be found on the Biological Invasions  website. 

Related articles:

Soil- and waterborne Phytophthora species linked to recent outbreaks in Northern California restoration sites

Three new Phytophthora detection methods, including training dogs to sniff out the pathogen, prove reliable

Coordinated response to inadvertent introduction of pathogens to California restoration areas

Posted on Monday, March 22, 2021 at 10:08 AM
  • Author: Jacob Shea, UC Berkeley
Focus Area Tags: Environment

New mobile app identifies hazardous trees for public safety

The UC ANR mobile app Evalutree asks a series of questions then calculates a hazard score for trees. Oak tree failure photo from UC ANR Publication 3518 Oaks in the Urban Landscape

"Trees are poems that the earth writes upon the sky,” wrote Kahlil Gibran. But trees falling into power lines have sparked catastrophic fires and falling trees have injured nature lovers.

To prevent power outages, PG&E looks for trees near power lines that need to be trimmed or removed. To prevent power outages and other mishaps caused by failing trees, Matteo Garbelotto, UC Cooperative Extension forest pathology specialist at UC Berkeley, has incorporated science into a mobile application that can be used to determine whether a tree presents a hazard and should be removed.

“PG&E was doing tree surveys with pencil and paper,” said Garbelotto, who saw the manual process as fraught with opportunities for error. A paper record needs to be sent to a central collection site where it is transcribed. In the transcription process, mistakes can be made. And there's no way of verifying if a person actually examined the tree to fill out the form.

Ph.D. student Mike Johnson uses Evalutree to assess the health and economic value of oak woodlands.

“Why don't you do a digital survey?” he asked a PG&E tree surveyor. “Using a tablet or phone, the data could be shipped directly, in real time, to the San Francisco office. Using a phone or GPS device, you will know the precise location of the tree and know the worker did the job. If there's a fire, you have proof.”

PG&E Corporation Foundation, the philanthropic arm of the utility, gave Garbelotto a $70,000 grant to develop the app he envisioned for determining which trees are hazards.

“Developed by dedicated UC Berkeley researchers, the tool will provide benefits for other utilities and the forestry industry as they work to create safe and healthy forests. The easy-to-use mobile platform collects data in real time and creates a record that the survey was completed including relevant details like “when,” “where” and “who,” said Stephanie Isaacson, director of community relations for PG&E.

The UC Cooperative Extension tree disease expert created a list of questions that help evaluate tree health. For example, in addition to asking if the tree leaning toward a power line, surveyors are asked, Are there obvious signs of internal decay? Is there a large wound on the tree?

“If a tree has a wound of 5 inches or more, there is a good chance there is significant decay behind the wound,” Garbelotto said. “If there is a mushroom or conk growing on the tree, that portion of the tree is dead and the branch or whole tree may fall down.”

The app, which Garbelotto has dubbed “Evalutree,” can be used for more than powerline safety.

The app generates a tree hazard map.

UC Berkeley Ph.D. student Michael Johnson has been using the app to evaluate different species of trees.

“We have just started our third field season using the app on a project for the Department of Defense that quantifies the health and economic value of the oak woodlands on the 100,000-acre Vandenberg Air Force Base,” said Johnson. “We started with coast live oak the first summer, added tanoak the second summer, and have expanded to bishop pine this summer.” 

The mobile app has simplified data collection for Johnson, who is in the Forest Pathology and Mycology Lab at UC Berkeley.

“I used pencil and paper studying postfire aspen regeneration on Forest Service land in Northern Arizona in 2012-2013, where I also did my master's work on ponderosa pine decay in 2013-2015,” Johnson said.

He described his undergraduate work collecting data with pencil and paper carried in a tatum, a 8.5-inch by 12-inch metal case with a clipboard, compared with working with the Evalutree phone app.

“Each day would start with making sure that we had all of our data sheets packed in our bulky field tatums,” Johnson said, “making sure our GPS points were preloaded in a separate, expensive GPS device, making sure that our camera had batteries and that we had dry erase markers for our small white board so that we could indicate which plot each photograph belonged to. 

“After the fieldwork was complete, we would spend weeks doing data entry, trying to make out the scrawled numbers and notes – smeared with charcoal and raindrops – and sorting and compiling the data, photos and GPS points. It was time-consuming and painstaking, to say the least.”

For his graduate research, Johnson was able to enter data directly into a spreadsheet on a field computer. “At the end of the field work, I would just have to compile the data from the computer, photos from the camera, and GPS points from the Garmin to make a report,” he said. 

“Evalutree has changed all of that. Instead of field tatums and multiple bulky devices, I walk out into the field with a lab cell phone. The app has preloaded survey questions, the ability to connect photographs to specific plots, and drops GPS points at each plot and tree that I survey.” 

Evalutree's assessment process leads to a tree hazard rating.

Working in the U.S. Defense Department's sprawling, undeveloped landscapes, Johnson said, “We are often in the field all day without internet or phone connectivity. The app is prepared to meet this challenge and relies on our phone's internal storage and pre-existing GPS functionality to order and store our data with precision accuracy. At the end of the day – when we have returned to civilization and technology – we simply upload all of our surveys for the day and I immediately have my data and reports in multiple formats, including pdf, xls and kml files, at my fingertips. 

“Within minutes, I can update my maps to show the exact location of all of the day's surveys, start crunching data in Excel, or print out a report with the photographs from each plot for my boss,” Johnson said. 

Garbelotto, the UC Cooperative Extension specialist, would like to make the technology available to cities and companies that manage trees.

“The app can be used by any agency or government that owns or manages a significant number of trees and needs to run surveys on a regular basis to ensure these trees are not at risk of failing, causing property damage or, worse,  casualties or injuries to people,” Garbelotto said.

“The surveys can be easily customized for different projects,” he said. “It can be used for campgrounds or parks to calculate the likelihood of a tree failing and likelihood of causing damage. You could have an answer within minutes of submitting the survey.” 

For more information about Evalutree, contact Garbelotto.

This story was updated July 21 to add a quote from PG&E.

Posted on Tuesday, July 21, 2020 at 11:01 AM

Citizen science SOD Blitz starts April 11 with new COVID-19 safety measures

Matteo Garbelotto examines bay laurel for sudden oak death symptoms at the UC Berkeley campus.

With Californians sheltering in place to stop the spread of new coronavirus COVID-19, the annual citizen science project to map sudden oak death disease has been redesigned to ensure the safety of participants. The first in a series of SOD blitzes of 2020 will be April 11 in Napa. The events are free.

“We have been able to redesign the 2020 SOD Blitzes to make them a safe and legal activity that allows volunteers to exercise outdoors, and this powerful citizen science program will help us protect our forests' health,” said Matteo Garbelotto, UC Cooperative Extension forest pathology specialist and adjunct professor in the Department of Environmental Science, Policy and Management at UC Berkeley and event organizer.

Sudden oak death disease has killed more than 50 million of the state's iconic oaks and tanoak trees between Humboldt County and Monterey County, threatening survival of several tree species. In 2019 alone, 1 million tanoaks succumbed to sudden oak death, according to 2019 tree mortality data released by the U.S. Forest Service.

“The presence of new SOD strains is alarming and the SOD blitzes are the best, if not the only, program to intercept them before they spread,” Garbelotto said.

SOD Blitz volunteers will register online and take the training online at to learn how to identify SOD symptoms and to carefully collect symptomatic leaves from California bay laurels and tanoaks. Collection and survey materials, which have been prepared in a sterile environment, will be picked up by participants at a local SOD Blitz station conveniently located near a parking lot. They can return samples to the same SOD Blitz station or by mail.

As citizen scientists, volunteers should focus on following safety guidance as well as adhering to research protocols. Social distancing – at least 6 feet away from other volunteers – and clean “housekeeping” rules will be strongly enforced when picking up or returning materials and during leaf collection.

For parents who are home schooling their children, this is an activity that the family can do together. 

Garbelotto encourages tree care specialists to participate in the SOD blitzes.

“Besides offering free bay laurel and tanoak tests for their clients, we now offer tree care professionals free enrollment in UC Berkeley Forest Pathology Laboratory's OakSTePprogram, which allows them to test oaks for SOD infection,” Garbelotto said.

For more information, visit or email the organizer of the SOD Blitz in your community (See schedule below).

Symptoms of sudden oak death disease on a bay laurel leaf.

Sudden Oak Death Blitzes 2020

All collection materials will be provided, but participants need a mobile phone or GPS device to install the free SODmap mobile app. 

New format due to COVID-19

1. Training (30 minutes) and sign-up (5 minutes) must be done online at before collecting the sampling materials at the SOD Blitz Stations in the locations specified below. Please sign up before you start the survey, and preferably when you take the online training.

2. Once at your local SOD Blitz Station you can pick up one or two collection packets following the social distancing rules of the State of California clearly specified in the online training.  Stay at least 6 feet from other collectors. Bring your own pencil. Each packet allows you to sample 10 trees. Do not pick more unless you discussed it with the organizer. 

3. Before you start the survey, make sure you have downloaded the free App “SODmap mobile” to determine the exact location of the trees you sample.

4. Each SOD Blitz has a start and end date, including the hour. You can pick up materials at the start time and you have to return your samples and any unused collection materials by the end date and cutoff time.

5. You can sample private properties with the owner's permission, alongside public roads and in parks or open spaces that are open to the public. 

6. If you have any questions, please email your local organizer. Thank you so much for your participation.

Napa Blitz

Saturday, April 11 at 10 a.m. to Tuesday, April 14, 10 a.m.

SOD Blitz Station located on front porch of the Napa County Agriculture Commissioners Office Building 1710 Soscol, Napa

Please mail samples to UC Berkeley using the preprinted mail labels and postage included in each packet.         

Contact: Bill Pramuk

For a schedule of SOD Blitzes at other locations, visit

Posted on Friday, April 3, 2020 at 2:05 PM
Focus Area Tags: Environment

Volunteers needed to stop SOD from killing oak trees

Dead tanoaks surrounded by Douglas firs in Humboldt County. Sudden oak death threatens survival of several tree species. Photo by Yana Valachovic

The mobile app SODmap shows trees that have been sampled. The red pins indicate the tree tested positive for SOD.
In California, sudden oak death disease has killed more than 50 million of the state's iconic oaks and tanoak trees between Humboldt County and Monterey County, threatening survival of several tree species. In 2019 alone, 1 million tanoaks succumbed to sudden oak death (SOD), according to 2019 tree mortality data released by the U.S. Forest Service.

“Two new dangerous SOD strains are at the doors of our forests,” said Matteo Garbelotto, UC Cooperative Extension forest pathology specialist in the Department of Environmental Science, Policy and Management at UC Berkeley. To assess the movement of SOD, he has mobilized citizen scientists for what he calls “SOD blitzes.” The first in a series of SOD blitzes of 2020 will be April 11 in Napa.

“We had some great results last year and participation continued to be good after 13 years of SOD blitzes,” Garbelotto said.

In Sonoma County, the 2019 SOD infection rate doubled that of 2018, and in Napa County, SOD detection was four times higher than the previous year. In the East Bay, between Richmond and San Leandro, SOD infection spiked – from 1% to 12%. The SOD infection rate tripled – from 6% to 18% on the western slopes of the Santa Cruz Mountains in San Mateo County.

Phytophthora ramorum, the pathogen that causes SOD, most often spreads on the leaves of infected California bay laurel (shown here) and tanoak.

As the disease expands its path of forest destruction, the UC Cooperative Extension scientist says more volunteers are needed to sample trees.

“The disease is moving to new counties outside of the current area of infestation,” Garbelotto said. “Even in our Bay Area neighborhoods, SOD of 2019 is not the same SOD of 10 years ago: different distribution, new local outbreaks, and new hosts are emerging, as the disease becomes more and more established in its new home.”

Garbelotto sees the SOD blitzes as the only hope for early detection of the new SOD strains.

SOD blitz volunteers are trained to identify SOD symptoms and to carefully collect symptomatic leaves from bay laurels and tanoaks. Photo by Doug Schmidt

“If these new strains arrived and spread in our forests, they could deliver a fatal blow to our forests,” he said. “By collecting symptomatic plant material in their neighborhoods, volunteers will make the most significant contribution possible to intercept these strains.” 

Volunteers are taught to identify SOD symptoms and to carefully collect symptomatic leaves from California bay laurels and tanoaks. Participants in the SOD blitzes will be asked to quantify their efforts to stop SOD to show public interest in saving oaks and tanoaks when applying for funds to defeat the tree-killing disease.

Garbelotto is encouraging tree care specialists to participate in the SOD blitzes.

“We have enhanced the benefits for tree care professionals who participate in the blitzes,” Garbelotto said. “Besides offering free bay laurel and tanoak tests for their clients, we now offer them free enrollment in UC Berkeley Forest Pathology Laboratory's OakSTeP program, which allows tree care professionals to test oaks for SOD infection. It could be enormously beneficial to everybody.”

For more information about the SOD blitzes, visit or See the 2020 SOD Blitz schedule at

Posted on Monday, March 9, 2020 at 9:01 AM

2019 SODBlitz shows Sudden Oak Death on the rise in California

Sudden Oak Death (SOD), a serious exotic tree disease, threatens the survival of tanoak and several oak species in California. Currently, SOD infects trees in 14 coastal California counties, from Monterey to Humboldt. The disease, which was estimated to have killed over 50 million oaks and tanoaks over two decades, has changed the coastal forests composition in Northern California and Southern Oregon.

Though SOD occurs in patches, the overall infection area continues to grow with each passing year. Researchers had previously discovered that Phytophthora ramorum, the pathogen that causes SOD, most often spreads on the leaves of infected California bay laurel and tanoak. Forest managers can use proactive methods for controlling the disease — including sanitation, chemical treatments, and the targeted removal of bay trees — but such tools are preemptive in nature, only useful before oaks and tanoaks are infected. Timely detection of the disease in these species is therefore critical to slowing the epidemic.

UCCE specialist Matteo Garbelotto refers to a resource provided to citizen science volunteers who participate in the 2019 SOD Blitz. More than 400 participants helped gather data this year. (Photo: Jim Block)

With this in mind, UC Berkeley joined with over 30 local organizers in 2019 to assemble 25 SOD Blitzes staffed by trained volunteers. More than 400 volunteers were taught to identify SOD symptoms and to carefully collect symptomatic leaves from California bay laurels and tanoaks. Armed with this training, the teams surveyed 16,227 trees across 16 California counties, collecting approximately 9,000 leaves from 1,732 symptomatic trees. Samples were sent to the UC Berkeley Forest Pathology and Mycology Laboratory for processing and analysis.

The benefits of SOD Blitzes are becoming increasingly clear. Importantly, they educate the community about Sudden Oak Death, getting locals involved in detecting the disease while creating detailed maps of infected areas. Analyses of these maps help forest managers figure out where proactive measures, such as chemical treatments or tree removal, most effectively stop an infestation. All results from the data collection are made publicly available on, and on the SODmap mobile app available at the Apple Store and at Google Play. (Results can also be accessed directly on the UC Berkeley Forest Pathology and Mycology Laboratory website.)

Using the app allows anyone to estimate the risk of oak infection, specific to their current location. While standing next to a tree of interest, a person can tap the app's “RISK” button and determine whether an oak is in danger of contracting SOD. In addition, results meetings and treatment training workshops will be held for the public in various Bay Area locations during fall 2019.

Matteo Garbelotto, UC Cooperative Extension specialist and adjunct professor in the Department of Environmental Science, Policy, and Management, has led the SOD Blitzes for 12 years. The program enrolls approximately 500 volunteers yearly to canvas California woodlands for symptoms of SOD.  Results of the surveys are made available nearly in real-time, immediately after completion of the lab analysis.

“We estimate that as many as two to three million people may have accessed the SOD Blitz results to determine whether trees on their property may be at risk,” Garbelotto said. “This is a huge success and shows the great societal value that citizen science has, and it highlights the importance of collaborating with volunteers on issues that are relevant to safeguard trees that are an important part of California's natural heritage.”

2019 SOD Blitz Results

Across the state, the number of trees infected with SOD, along with the estimated SOD infection rate, has almost doubled since 2018. In some areas, infection rates were as much as 10 times higher than the previous year. These results suggest that the overall risk of oak infection by SOD is rising.

Spikes in the estimated SOD infection level at certain locations are particularly noteworthy; for example, from 1 to 12 percent in the western part of the East Bay between Richmond and San Leandro, including distinct outbreaks discovered in El Cerrito, Kensington and Berkeley. The western slopes of the Santa Cruz Mountains in San Mateo County have also seen an increase in SOD infection rate (from 6 to 18 percent), which may make safeguarding recreational venues and ecologically important forest sites more difficult. In Sonoma County, the 2019 SOD infection rate was approximately double that of 2018, and in the same timeframe, Napa saw a fourfold increase in detection. Peninsula towns between Redwood City and Los Altos Hills had a very high infection rate (21.6 percent) with an expansion of outbreaks to the east and north.

Some additional key results that came from the 2019 SOD Blitzes include:

  • Two tanoaks were positive for SOD in a state park east of Crescent City in Del Norte County, marking the first report of SOD for the county. This was an important finding because, until 2019, Del Norte was the only county free of the disease in the area between the vast California infestation and the Southern Oregon outbreak. The SOD Blitz finding does not have immediate implications for regulations, but regulations will be imposed once CDFA can confirm the finding.
  • An extensive survey of San Luis Obispo failed to identify SOD; however, multiple trees were found to be infected in the southernmost canyon of Monterey County. Previously, this canyon had only provided positive findings from water monitored by UC Davis scientists, but not from trees.
  • Although Humboldt County has a few significant SOD outbreaks, and Trinity County has a marginal SOD outbreak in its southwestern border, SOD Blitzes in tribal lands in Humboldt and Trinity counties did not yield any SOD positives.
  • San Francisco parks, including the Presidio, were negative for a second year in a row, suggesting that disease management practices have been successfully implemented in the area.
  • Several cases were identified in the northern neighborhoods of the City of Napa. No positives had been found in this area since 2011.
  • All isolates of the pathogen belonged to the NA1 lineage, which is more easily treated and common in the region. This is good news because of uncertainty about the potential virulence of the EU1 lineage recently discovered in Oregon forests.

A sampling of other noteworthy 2019 SOD Blitzes results follow. More results are available on the websites and app:

  • The first infected Bay laurel was identified a few miles east of the town of Mendocino (Mendocino County) along the Comptche-Ukiah Road.

  • Multiple SOD positive trees were identified between Guerneville and Duncan Mills in Sonoma County. The Russian River area has long been known to be affected by SOD.
  • An outbreak was identified in southwestern Petaluma, while infestations were confirmed in Bennett Valley, Santa Rosa and east of Rohnert Park.
  • Multiple infestations were identified in Marin County, including the ones northeast of San Rafael, Larkspur, Woodacre, Mount Tamalpais, Marin City and north of Inverness.
  • In the Peninsula, SOD was identified in Burlingame Hills, northern Woodside, Emerald Hills, Palomar Park, Portola Valley. In Los Altos Hills and Loyola, SOD positive trees were detected both East and West of Interstate 280. An outbreak was detected west of Saratoga.
  • High levels of infection were identified all along Skyline between Bear Gulch Road and Highway 17, and on the western slopes of the Santa Cruz Mountains between Skyline and Pescadero.
  • SOD was confirmed between Felton and Santa Cruz and between Aptos and Santa Cruz.
  • In Monterey County, the chronic Big Sur outbreak was once again confirmed to be active, while the disease appeared also in drier areas of the Carmel Valley, where it had been absent for a few years.

The SOD Blitz program was funded in part by the U.S. Forest Service's State and Private Forestry Organization and by the Midpeninsula Regional Open Space District. It was also made possible by a collaboration with the California Native Plant Society, CalFire, the Humboldt/Del Norte and Sonoma County UC Cooperative Extension, the Sonoma County UC Master Gardeners, the U.S. National Parks, California State Parks, the East Bay Regional Parks, the San Francisco Public Utility Commission, Mid-Pen Open Space, the UC Santa Cruz Arboretum, Santa Cruz Open Space, the Santa Lucia Conservancy, the Karuk and Hoopa Nations, the Mendocino Botanical Garden, the City and County of San Francisco Parks and Recs Office, and Strybing Arboretum. Many individuals, who have generously devoted their time and efforts, have been pivotal for the existence and success of the program.



Posted on Thursday, November 14, 2019 at 8:36 AM
Tags: Matteo Garbelotto (20), SOD (6), Sudden Oak Death (38)
Focus Area Tags: Environment

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