Sudden oak death (Phytophthora ramorum) and utility hazard trees
Phytophthora ramorum kills tanoak and red-group oaks and only spots the leaves of bay laurel, redwood and Douglas-fir. The rule reaching a line clearance crew is 3 CCR 3700, a CDFA quarantine over sixteen entire counties governing intrastate movement of host wood and chips. Infected coast live oaks failed at 34 percent against 3.5 percent for symptom-free trees.
A coast live oak dies over a 12 kV span in Napa County. Felling it is the simple part. What goes wrong afterward is the chip truck, because from the moment that wood is on the trailer it is a regulated article, and the boundary the regulation cares about is the county line.
Sudden oak death is caused by Phytophthora ramorum. It gives a line clearance program two obligations that sit in two different codes and answer to two different agencies. One is a hazard tree that loses strength faster than most inspection cycles run. The other is a quarantine that decides where the debris is allowed to go.
The rule that reaches the chipper is a CDFA quarantine
California's instrument is 3 CCR 3700, Oak Mortality Disease Control. It names the pest in one line and the ground in the next:
(b) Regulated Area. The regulated area for the pest is: The entire counties of Alameda, Contra Costa, Del Norte, Humboldt, Lake, Marin, Mendocino, Monterey, Napa, San Mateo, Santa Clara, Santa Cruz, San Francisco, Solano, Sonoma and Trinity.
Sixteen entire counties, and the whole county is the unit every time. Del Norte is the newest of them, added by emergency regulation and then made permanent by an amendment filed with the Secretary of State on November 17, 2021 and effective the same day.
What the regulation covers includes the material a removal produces:
(3) Unprocessed wood and wood products (including but not limited to bark chips, mulch and firewood -- except when completely free of bark) of the plants listed in paragraph (c)(1) as bole hosts and plant products of the plants in paragraph (c)(1)
The restriction runs one direction. Covered articles are prohibited movement out of the regulated area except under an official certificate, a permit from an authorized agricultural official specifying containment conditions, or direct-route through-movement of material that originated outside the area. Inside the sixteen counties, the regulation is silent.
So the practical test at the end of the shift is not whether the tree was diseased. It is which county the truck unloads in. A circuit that leaves Napa County heading east ends in Yolo County, which sits outside the regulated area, and a load of oak chips crossing that line without a certificate or permit is the violation.
Sonoma County is ringed entirely by regulated counties, and the same crew working there all week stays clear of the question by geography alone. Where a permit is refused, 3 CCR 3700(e) gives seven calendar days to appeal, a hearing within 48 hours of a timely appeal, and a decision within 24 hours of the hearing.
The federal quarantine governs interstate movement only
The federal rule is easy to reach for and wrong for this job. 7 CFR 301.92-2(b)(1) names exactly the material a crew generates:
Nursery stock, decorative trees without roots, unprocessed wood and wood products, and plant products, including firewood, logs, lumber, wreaths, garlands, and greenery of proven host plant taxa
But 7 CFR 301.92-4(a) is headed "Interstate movement of regulated and associated articles from quarantined areas," and it governs movement out of the state. Bark chips and mulch are handled harder still. Section 301.92-2(a)(1) makes them a restricted article, and 301.92-4(b)(1) lets a restricted article move interstate only under a permit issued under 7 CFR part 330.
All of that stops at the state line. A truck running Napa to Yolo answers to 3 CCR 3700, and the official who enforces it is the county agricultural commissioner.
January 1, 2027: the host list moves out of the regulation
CDFA has completed a rulemaking that changes how 3 CCR 3700 identifies a host. The schedule is published on CDFA's own regulations page.
Step | Date |
Noticed in the California Regulatory Notice Register | March 13, 2026 |
Comment period on the modified text | July 9 to July 24, 2026 |
Submitted to the Office of Administrative Law | July 29, 2026 |
Filed with the Secretary of State | September 8, 2026 |
Effective | January 1, 2027 |
The change deletes the species list printed inside the regulation and replaces it with a pointer:
(1) Plants and plant parts (except acorns or seed) listed in the document "APHIS Lists of Proven Hosts of and Plants Associated with Phytophthora ramorum",pages 1-6, dated September 2022, which is hereby incorporated by reference.
Anyone who has learned to read the current list should notice one thing. The version in force today uses an asterisk to mean that the bole is included, which is why tanoak, coast live oak, canyon live oak, California black oak and Shreve's oak all carry one. The incorporated APHIS document uses the same symbol for the opposite proposition:
Unmanufactured wood and wood products, including firewood, logs, and lumber of species listed above are not regulated. See Federal Regulations, 7 CFR 301.92 - 301.92-2
In that document tanoak carries an asterisk and coast live oak stands clean. Same symbol, same species, reversed meaning, in two documents that will both be findable online next year. That question belongs to the county agricultural commissioner for the destination county, asked before the truck is loaded.
Two California county lists, and they disagree in three places
The quarantine list is one of two county lists California maintains for this pathogen. 14 CCR 1052.1(a)(6)(E), in the Forest Practice Rules, limits the "isolated infestation" emergency condition to fifteen counties.
County | In the CDFA quarantine, 3 CCR 3700(b) | In the Forest Practice Rules, 14 CCR 1052.1(a)(6)(E) |
San Francisco | Yes | No |
Trinity | Yes | No |
San Luis Obispo | No | Yes |
A San Luis Obispo County crew sits outside the movement quarantine and inside the list that triggers a forestry emergency condition. Both lists are correct. They answer different questions, written by different agencies under different statutes, and the working habit is to name which one you are reading.
The pathogen kills five hosts and only spots the rest
CDFA's own statement of reasons for the 2026 amendment sets out the division:
Since the mid-1990s, Phytophthora ramorum has killed millions of tanoak trees and several oak tree species (coast live oak, California black oak, Shreve oak, and canyon live oak), and caused twig and foliar diseases in numerous other plant species, including California bay laurel, Douglas fir, and coast redwood.
Species | What the pathogen does | Killed |
Tanoak, Notholithocarpus densiflorus | Bole canker, fastest decline of any host | Yes |
Coast live oak, Quercus agrifolia | Bole canker, slower decline, failure while green | Yes |
California black oak, Quercus kelloggii | Bole canker | Yes |
Canyon live oak, Quercus chrysolepis | Bole canker | Yes |
Shreve's oak, Quercus parvula var. shrevei | Bole canker | Yes |
California bay laurel, Umbellularia californica | Leaf spots, and the main source of inoculum | No |
Coast redwood, Sequoia sempervirens | Needle and shoot lesions | No |
Douglas-fir, Pseudotsuga menziesii var. menziesii | Needle and shoot lesions | No |
Valley oak, blue oak, Oregon white oak | Not thought to be susceptible | No |
Two consequences follow for anyone carrying an inventory. The white oaks sit inside a different problem, which is why Mediterranean oak borer and sudden oak death describe separate stems. And the species that survives this pathogen is the species that spreads it, which makes coast redwood and Douglas-fir in a corridor relevant as carriers rather than as casualties. The California Oak Mortality Task Force's August 2025 Del Norte County surveys returned positives from tanoak sprouts and branches and also from the foliage of bay laurel, coast redwood and Pacific rhododendron.
The failure rate is 34 percent against 3.5 percent
The number that matters to a hazard tree program comes from a seven-year case-control study by Ted Swiecki and Elizabeth Bernhardt of Phytosphere Research. They read 150 circular plots of 8 meter radius at 12 locations in Marin, Sonoma and Napa Counties, every September from 2000 through 2006.
Between 2000 and 2006, the failure rate of trees that had SOD symptoms in 2006 (34%) was about 10 times that of trees that remained free of P. ramorum canker symptoms (3.5%). The failure rate among tanoaks that developed P. ramorum canker symptoms by 2006 was 26%, compared with a 3% failure rate in tanoaks that were asymptomatic in 2006.
That is the whole case for treating a confirmed canker as a structural finding rather than a plant health note. The same report gives the clock on tanoak. Of the tanoaks that first became symptomatic between 2001 and 2006, 33 percent died within 2 years of the symptoms appearing.
Coast live oak already carries the longest documented failure record of any species on California circuits. This pathogen multiplies that baseline by ten on the trees it has infected.
Failure comes before death, and soon after it
The same study records where the failures start:
Nearly three quarters of the initial substantial failures in SOD-affected coast live oaks occurred in dead trees or dead stems of live trees. However, in live coast live oak trees with P. ramorum canker, more than half of the observed initial failures occurred in live stems or branches.
The Sudden Oak Death Guidelines for Arborists, issued by the California Oak Mortality Task Force in July 2021, states the timing:
The wood of P. ramorum-infested trees appears to decay rapidly, often resulting in failure within a few months of dying. Diseased trees heavily colonized by bark and ambrosia beetles and the Hypoxylon fungus may fail before they have died (while they are still green).
Set that against the interval between visits. A tree found green and symptomatic in March can be structurally unsound by August while the record still shows it standing and alive. The findings that carry the risk all sit on the lower trunk: the bleeding canker, the Annulohypoxylon thouarsianum fruiting bodies on the bark, and the beetle boring dust in the fissures.
A crown assessment made from the road misses every one of them. What the ground inspection is looking for, and at what level, is settled in the field hazard tree assessment the program specifies. On this species it is looking at bark at eye height.
The guidelines put the climbing hazard ahead of the reliability hazard:
Oak and tanoak trees infected or killed by P. ramorum are prone to rapid decay and unpredictable failure. Arborists and other tree care professionals need to be very cautious about climbing P. ramorum-infected or killed trees.
The bay laurel under the conductor is the inoculum source
California bay laurel survives this pathogen and is the reason oaks near it die. Swiecki and Bernhardt measured the geometry on 247 coast live oaks and published it in the Proceedings of the Sudden Oak Death Third Science Symposium, PSW-GTR-214, pages 181 to 194:
Disease risk and severity were greatest at bay foliage-oak trunk distances of 1.5 m or less and were minimal at a distance of 10 m or more. Bay cover within 2.5 m of the trunk was a stronger predictor of disease risk and severity than the minimum bay-trunk distance.
In feet that is roughly 5 feet for maximum risk, 8 feet for the cover measurement that predicts best, and 33 feet for the distance at which risk goes small. The COMTF arborist guidance turns the same finding into two round numbers: consider removing bay laurels whose canopies sit within 15 feet of the trunks of valued oaks, and when pruning major limbs over 4 inches diameter, consider taking bay branches within 8 feet.
This is the one place where the clearance work and the disease work point the same direction. A directional prune that takes bay canopy out from under a primary removes some of the foliage that drips inoculum onto the oak standing 20 feet away. Record it as a side effect. GO 95 Rule 35 and PRC 4293 are silent on the pathogen, and a bay outside the clearance envelope stays where it is.
What happens to the material, and what that collides with
The COMTF guidance for work inside the quarantine area runs tighter than the regulation:
Within the quarantine area, host material (e.g., wood, bark, brush, chips, leaves, or firewood) from tree removals or pruning of symptomatic or non-symptomatic host plants should remain on site to minimize pathogen spread.
Three further practices come with it. Schedule removals June to October and hold diseased-tree removal out of November to May, when wet conditions favor spread. Skip the stump grinder, because the equipment picks up contaminated soil and carries it to the next job. Clean mud, leaves and woody debris off the chipper and the trucks before leaving the site.
Two of those collide with the rest of the work. Leaving host chips under the span runs against what a site clean standard grades, and it adds surface fuel inside a corridor that may also owe a PRC 4292 pole clearing. The June-to-October window is the same window that already carries the pre-fire-season push and sits inside a calendar with several other seasonal locks on it. Both conflicts get resolved locally. The COMTF document is guidance, and the utility's own vegetation specification decides which practice wins on the day.
The one rule written for this pathogen is a timber instrument
California does have a regulation aimed squarely at controlling sudden oak death in the field. It is 14 CCR 1052.5, Emergency Notice for Outbreaks of Sudden Oak Death Disease, in the Forest Practice Rules, and it carries a distance in feet:
(4) designate for treatment or removal the host hardwood species in the infested areas and within 330 feet of the infestation area to control the spread of SOD consistent with Forest Pest Specialist concurrence in (3) above;
Everything about that instrument belongs to somebody else. A Registered Professional Forester prepares it. It requires certified lab testing results confirming P. ramorum. It requires written concurrence from a Department Forest Pest Specialist. Subsection (c) incorporates the COMTF Sudden Oak Death Guidelines for Forestry, revised August 2010, by reference, which makes a guidance pamphlet part of the rule for anyone filing one.
The same title places utility work elsewhere. 14 CCR 1104.1(c) exempts this from the Conversion Permit and Timber Harvesting Plan requirements of that article:
The clearing of trees from Timberland by a private or public utility for construction of gas, water, sewer, oil, electric, and communications (transmitted by wire, television, radio, or microwave) rights-of-way, and for maintenance and repair of the utility and right-of-way.
That exemption is capped by the rule's own Table of Normal Rights-of-Way Widths, which is the table discussed in right-of-way width and easement width. So the 330-foot designation and the Forest Pest Specialist concurrence both live inside a harvest document, and a crew standing under a conductor with a dead tanoak in front of it files neither. Authority to cut comes from the easement and the clearance rules. The only sudden oak death instrument that reaches the work is the CDFA quarantine, and it reaches the truck.
What a sudden oak death record has to carry
An entry reading "dead oak, removed, Sonoma County" survives an audit of the clearance and leaves the next inspector nothing to act on. Seven entries make it usable, and each one traces to something published above.
Entry on the form | Why it earns its space |
Binomial, down to variety where the species splits | Killed host, foliar host, and outside the problem are three different dispositions |
Origin county, plus the county the load ends in | Whether 3 CCR 3700(d)(1) is engaged at all |
Symptom seen, with its height on the bole | Canker, Annulohypoxylon fruiting bodies and boring dust are lower-trunk findings |
Crown condition, logged in its own line | A canker stands on its own evidence, and failures happen in live stems |
Measured gap from nearest bay foliage to the oak trunk | The 1.5, 2.5 and 10 meter thresholds from the published study |
Where the wood and chips ended up, by destination county | The certificate or permit question, answered before the load moves |
Observation date, and the observer by name | Decay runs in months, so the age of the finding is part of the finding |
One tree, entered: pole and span identified, 12 kV, circuit named, Marin County. Quercus agrifolia, 31 inches diameter at breast height, two scaffolds over the primary. Examined on foot on June 16 by a named Consulting Utility Forester. Bleeding canker on the north face of the bole at 4 feet, approximately 18 inches long, with three Annulohypoxylon thouarsianum fruiting bodies within 2 feet of it and fine boring dust in the bark fissures below. Crown full and green.
Nearest California bay laurel foliage approximately 4 feet from the trunk, canopy overhanging the conductor. Prescribed as a removal under the utility specification rather than a prune, per the removal-or-prune call that specification governs. Work scheduled July rather than deferred to the fall cycle. Wood and chips retained on site below the pole clearing, destination county Marin, stump cut low and the grinder left on the truck.
Every clearance requirement on that span was satisfied the day the tree was last pruned. The quarantine asked only about the truck, and GO 95 asked only about the wire. What the entry buys is the September look at the same stem, and on a species that can fail with a green crown, that look is the entire margin.
Further reading
Coast live oak in the utility right of way: The host with the longest documented failure record on California circuits, and where those failures start.
Mediterranean oak borer: the emerging North Bay oak threat: The other North Bay oak problem, on the white oaks this pathogen is thought to leave alone.
Seasonal restrictions on California utility vegetation work: The calendar the June-to-October removal window has to fit inside.
Frequently asked questions
Which California counties are under the sudden oak death quarantine?
Sixteen entire counties, named in 3 CCR 3700(b): Alameda, Contra Costa, Del Norte, Humboldt, Lake, Marin, Mendocino, Monterey, Napa, San Mateo, Santa Clara, Santa Cruz, San Francisco, Solano, Sonoma and Trinity. Del Norte was the most recent addition, made permanent by an amendment filed with the Secretary of State on November 17, 2021 and effective the same day. The regulated area is the whole county in every case, so the county line is the only boundary to check.
Can a crew haul chips from a sudden oak death removal across a county line?
Out of the regulated area, only under one of the three conditions in 3 CCR 3700(d)(1): an official certificate, a permit from an authorized agricultural official specifying containment conditions, or movement that originated outside the regulated area and passes through by direct route without delay. Within the sixteen-county area the regulation imposes no movement restriction. The federal rule at 7 CFR 301.92-4 governs interstate movement, so a Napa to Yolo haul answers to the California regulation and the county agricultural commissioner. California Oak Mortality Task Force guidance goes further than either rule and asks that host material from removals or pruning stay on the site it came from.
Can a sudden oak death tree fail before it dies?
Yes. The California Oak Mortality Task Force states that trees heavily colonized by bark and ambrosia beetles and the Hypoxylon fungus "may fail before they have died (while they are still green)." In the Swiecki and Bernhardt case-control study, more than half of the first observed failures in live coast live oaks carrying P. ramorum canker occurred in live stems or branches.
Does removing bay laurel for clearance help the oak next to it?
It can. Risk and severity of P. ramorum canker in coast live oak were greatest where bay foliage sat 1.5 meters or less from the oak trunk and minimal at 10 meters or more, and bay cover within 2.5 meters of the trunk predicted risk better than minimum distance did. A directional prune that takes bay canopy out from under a conductor removes some of the foliage that rains inoculum onto nearby oak trunks. Treat that as a side effect of the clearance work rather than as a prescription.
Is there a California rule written specifically for sudden oak death control?
14 CCR 1052.5, Emergency Notice for Outbreaks of Sudden Oak Death Disease. It is a Forest Practice Rules instrument, prepared by a Registered Professional Forester, requiring certified lab results and written concurrence from a Department Forest Pest Specialist, and it designates host hardwoods for removal within 330 feet of the infestation area. It governs Timber Operations. A utility clearing its own right of way for maintenance is exempt from the Conversion Permit and THP requirements under 14 CCR 1104.1(c).
