Bark beetle complexes and conifer mortality in utility corridors
A beetle-killed conifer over a span is reached by CPUC General Order 95 Rule 35, which applies once the company has actual knowledge that dead, rotten or diseased trees overhang or lean toward the line. California's statewide Tree Mortality state of emergency ended March 24, 2026. On timberland, 14 CCR 1104.1(e)(3) adds clearance for Danger Trees.
A crew standing under a span in the northern Sierra in September is looking at conifers that were killed by an event the state formally closed out six months ago. The statewide Tree Mortality state of emergency was proclaimed on October 30, 2015. On March 24, 2026, Governor Newsom signed a proclamation terminating it, in a batch with open fire, storm and drought emergencies.
The standing dead are still standing. What changed on that date is where the obligation comes from. A line-clearance program that built its dead-conifer workflow on the emergency now has to point at the instrument underneath it, and that instrument is one paragraph of GO 95 Rule 35 that turns on two words: actual knowledge.
This piece covers the beetles that produce that knowledge problem, the interval between death and the appearance of death, and what may be cut and filed once the tree is identified.
The emergency ended on March 24, 2026, and the standing dead stayed up
The 2015 proclamation was built in two steps. Directive 1 told four agencies to draw the map:
The Department of Forestry and Fire Protection, the California Natural Resources Agency, the California Department of Transportation, and the California Energy Commission shall immediately identify areas of the State that represent high hazard zones for wildfire and falling trees using best available science and geospatial data.
Directive 2 then attached utilities to that map:
State agencies, utilities, and local governments to the extent required by their existing responsibilities to protect the public health and safety, shall undertake efforts to remove dead or dying trees in these high hazard zones that threaten power lines, roads and other evacuation corridors, critical community infrastructure, and other existing structures.
Read the qualifier in the middle. Even at the height of the emergency, the directive bound utilities only to the extent required by their existing responsibilities. It pointed at an obligation that already existed. What it did add was a map, a priority, and a procedural shortcut: directive 15 suspended CEQA, Division 13 of the Public Resources Code, for the purposes of carrying out directives 1, 2, and 5 through 8.
The termination proclamation prints the row plainly. Tree Mortality, 10/30/2015, Statewide. And it says what goes with it:
having found pursuant to Government Code section 8629 that the conditions of extreme peril to the safety of persons and property underlying the State of Emergency proclamations listed below no longer exist, therefore proclaim that the States of Emergency proclaimed on the following dates and in the following jurisdictions no longer exist, effective immediately. Accordingly, any Executive Order provisions related to the terminated states of emergency are no longer in effect.
Three things go. The high hazard zone trigger, the CEQA suspension for that work, and the proclamation's own priority language. The tally the emergency was built on stays useful as history: the proclamation recited a Forest Service estimate of over 22 million trees already dead in October 2015, with tens of millions more expected inside the year.
The paragraph that makes a dead conifer the company's problem
Rule 35 carries a separate sentence for dead wood, distinct from the clearance sentence a crew works to at the pole:
When a supply or communication company has actual knowledge, obtained either through normal operating practices or notification to the company, that dead, rotten or diseased trees or dead, rotten or diseased portions of otherwise healthy trees overhang or lean toward and may fall into a span of supply or communication lines, said trees or portions thereof should be removed.
It reaches the whole tree and the dead part of a live one. The trigger is the lean and the overhang, and the cause of death is left open. A beetle-killed white fir leaning toward a span is inside it for the same reason a storm-broken top is. The clearance side of Rule 35 is a different obligation with a different measurement.
Two words are worth sitting with. The clearance sentence says the minimum clearances shall be maintained. This sentence says the trees should be removed. The difference is on the page. What it amounts to in a proceeding is for the Commission, and Exception 3 to the same rule reserves that call explicitly, allowing the Commission to direct prompt remedial action "whether or not the nonconformance gives rise to penalties."
The operative phrase for a beetle program is the other one. The duty attaches on actual knowledge, and the rule names two ways that knowledge arrives: the company's own normal operating practices, or notification from somebody else. Rule 35 leaves the frequency of those practices to other instruments. The inspection cycle sets that, and what a patrol is required to see against what a detailed inspection adds decides whether a fading crown becomes knowledge this year or next.
A complex is several agents, and the beetle is often the last
The word in the title is the state's own. The 2025 California Forest Pest Conditions report uses it for the fir engraver, the beetle working on the true firs that made up more than 71 percent of the tree mortality that survey recorded in 2025:
While this beetle can kill true firs on its own, it is often part of a pest complex where several biotic agents including root disease, dwarf mistletoes, and other insects contribute to tree decline.
That matters at the pole because the beetle is frequently the last agent in a sequence. The same report records a pest complex of mountain pine beetle, stalactiform rust and dwarf mistletoe killing more than 30 lodgepole pine. It records fir engraver, woodborers and Armillaria root disease together killing roughly ten white firs over 30 inches in diameter at North Grove Campground.
The species a California program actually meets make a short list. UC IPM's Pest Notes Publication 7421 gives host and attack position for each, which is where on the stem a pre-inspector should be looking.
Beetle | Hosts on a California circuit | Where it attacks | Generations a year, UC IPM |
Western pine beetle (Dendroctonus brevicomis) | Coulter and ponderosa pines | Midtrunk, then spreads up and down | 2 to 4 |
Mountain pine beetle (D. ponderosae) | Pine, frequently lodgepole and sugar | Midtrunk of large trees, 5 to about 30 feet | 1 to 2 |
Jeffrey pine beetle (D. jeffreyi) | Jeffrey pine | Midtrunk of large trees, 5 to about 30 feet | 1 to 2 |
Red turpentine beetle (D. valens) | Pines, rarely fir | Lowest 2 to 8 feet of trunk and the large roots | 0.5 to 2 |
Engraver beetles (Ips spp.) | Pine | Near the top of the stem | 1 to 5 |
Fir engraver (Scolytus ventralis) | White and red fir | Deep two-armed galleries across the grain | 1 to 2 |
Cedar and cypress bark beetles (Phloeosinus spp.) | Arborvitae, cypress, junipers, redwood | Twigs, then trunk of dead or dying trees | 1 to 2 |
Douglas-fir beetle (D. pseudotsugae) | Douglas-fir | Windthrown stems and pathogen-infected live trees | unlisted |
Red turpentine beetle is the row most often over-read. UC IPM records that it rarely kills trees and that prominent pitch tubes on the lower trunk nearly always indicate its presence. Pitch tubes at four feet on a ponderosa record stress.
The concrete case for the complex is at Calaveras Big Trees State Park. Four sugar pines over 30 inches in diameter in the North Grove were mass attacked and killed by mountain pine beetle after a prescribed burn in spring 2024. The report records minimal trunk scorch and no crown scorch.
Thick duff around the bases let the fire sit on the roots and girdle the cambium below ground. The injury that invited the beetle sat under the duff line, out of reach of a ground inspection. A corridor produces the same injury by other means, through grading at a pole, trenching for a riser, or compaction under a track machine.
The tree is dead before it looks dead
This is the section that decides whether a program finds these trees or inherits them. UC IPM states the sequence plainly:
Frequently the infestation is diagnosed after the beetles have vacated the tree. For example, when reddish brown foliage is observed the tree is dead and the new generation of bark beetles has already emerged from the tree. Fading foliage throughout the tree crown indicates a dead tree and no insecticide treatment will be effective.
A red crown is a closed file. The signs that arrive earlier are physical and low on the tree:
Fresh pitch tubes on the bark surface.
Sawdust-like frass in bark crevices, on the ground, or caught in spider webs.
Yellow or yellow-green needles, which come before brown.
Emergence holes, which mean the brood has already left.
Two field errors run in opposite directions, and both are documented in the state's own reports.
The first is trusting a defense that held. Fresh fir engraver attacks near Yuba Pass on the Tahoe National Forest in 2023 showed heavy resin streaming, which reads in the field as the tree winning. The 2024 revisit found that about 30 percent of those trees had died or lost their tops. A pitched-out attack is a finding to re-inspect, not a finding to close.
The second is reading color as recency. The 2024 report records that new mortality on the eastern slopes of Mount Lassen was hard to separate from old, "due to prior years' dead trees retaining their dead needle complement for multiple years, especially red fir."
A red fir can hold brown needles across more than one inspection cycle. A crown carries condition, and the year of death has to come from somewhere else. A record that logs "red crown, 2026" for a tree that died in 2023 has started the failure clock three years late.
The survey a program used to lean on shrank by three quarters
For a decade, California programs have borrowed knowledge from the USDA Forest Service Aerial Detection Survey, which flies a 4 to 5 mile grid with two observers and sketch-maps recent mortality. In 2024 it covered 40.1 million acres and recorded elevated mortality on roughly a million of them, with approximately 5.2 million dead firs across 750,000 acres and approximately 810,000 dead trees over 150,000 acres attributed to western pine beetle.
The 2025 report opens its survey section differently:
Most of the Region was not surveyed in 2025, however approximately 9.8 million acres were surveyed ... Areas surveyed include the Southern Bay Area, Central Coast, and Southern California along with much of the Southern Sierra Nevada Range where the concurrent drought conditions were most severe.
Coverage fell from 40.1 million acres to 9.8 million. The northern interior, the northern Sierra and the north coast sit outside the 2025 numbers entirely. The report says so directly about the lingering mixed conifer mortality there: "It is unknown how this situation progressed since none of these areas were surveyed in 2025."
That has a specific consequence for Rule 35. Knowledge obtained through normal operating practices is the company's own practices. Where a program's dead-conifer prioritization has been drawing on ADS polygons, in most of the state the 2025 layer is blank, and a 2024 layer is now two flying seasons old. Whatever the system of record carries for those circuits this cycle was put there by a patrol, an inspector, or a customer call.
The failure clock starts at death, and the report comes later
A beetle-killed conifer becomes an urgent tree on a schedule, and the schedule is published. The summary in Knapp's study of long-term dead wood in Sierra Nevada mixed conifer is direct:
Most snags remain standing 5 years after tree death but then begin to rapidly fall between the 5th and 15th years (Keen, 1955). Larger diameter snags with higher amounts of heartwood generally fall more slowly than smaller trees with less heartwood (Keen, 1955). Rate of snag fall varies by species, with fir snags remaining upright longer, on average, than pine.
Three practical readings. A tree killed in the 2020 to 2022 drought is entering its rapid-fall window now. A fir stands longer than a pine of the same size, so a stand of standing dead fir is a longer-lived inventory problem than a stand of dead ponderosa. And the largest stems, which are the ones that reach a conductor from outside the cleared width, are the slowest to come down, which means they sit in the fall zone the longest.
Whole-tree failure is also the last event in the sequence. The tops and limbs go before the stem does, and a conductor strung under a crown meets the branches on the way. The fall-zone arithmetic for a tall conifer is set out elsewhere in this set, and it is the arithmetic that decides which of these trees is in scope at all.
What may be cut on timberland, and what is filed first
A distribution circuit in the Sierra frequently runs across classified timberland, and on timberland cutting trees is timber operations. The exemption a utility works under is 14 CCR section 1104.1, subsection (c):
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. The said right-of-way, however, shall not exceed the width specified in the Table of Normal Rights-of-Way Widths for Single Overhead Facilities and Single Underground facilities and the supplemental allowable widths.
The tabulated widths at 1104.1(d) are narrower than most crews expect.
Overhead electric, single circuit | Exempt width |
0 to 33 kV | 20 feet |
34 to 100 kV | 45 feet |
101 to 200 kV, pole | 75 feet |
101 to 200 kV, tower | 80 feet |
201 to 300 kV, tower | 125 feet |
301 kV and above, tower | 200 feet |
Twenty feet stops well short of a 120-foot white fir standing 60 feet off the centerline. The provision that reaches it is subsection (e)(3), which allows "Additional clearance for removal of Danger Trees as defined in 14 CCR § 895.1." That definition is the one that decides the question, and it was written for this exact situation:
"Danger Tree" means any tree located on or adjacent to a utility right-of-way or facility that could damage utility facilities should it fall where (1) the tree leans toward the right-of-way, or (2) the tree is defective because of any cause, such as: heart or root rot, shallow roots, excavation, bad crotch, dead or with dead top, deformity, cracks or splits, or any other reason that could result in the tree or main lateral of the tree falling.
Dead or with dead top is named in the list. A beetle-killed conifer adjacent to the right-of-way qualifies on the face of the definition, and the Forest Practice Rules allow it to be cut as a supplement to the 20 feet. The definition then points the reader at chapter VII of the Powerline Fire Prevention Field Guide, 1977, which is the reference text the regulation still cites.
The paperwork is a single form. RM-73, revised April 2025, is the Public Agency, Public or Private Utility Right of Way Exemption, filed through CalTREES or to the CAL FIRE Forest Practice Manager for the county. It names the Licensed Timber Operator, the timberland owner of record, the timber owner of record, the utility, and an on-site contact. Its terms are short and worth holding:
The Director determines within fifteen days of receipt whether the notice is complete and accurate.
No timber operations may be conducted until the notice of acceptance is received.
A valid copy of the notice and the acceptance stays on site during operations.
The exemption is valid for one year from the date accepted.
One year is the term to watch in a mortality event. A program that filed in March for a circuit it expects to revisit after the fall flight season is filing again.
The wood is brood material until somebody makes it otherwise
A felled beetle-killed conifer keeps its role in the outbreak. Freshly cut wood attracts beetles, and wood from a tree killed last season may still hold developing brood. There is no general California statute on the movement of bark beetle wood.
Public Resources Code section 4714.5 prohibits moving eucalyptus wood containing live eucalyptus longhorned borers or their larvae in trucks or trailers, and that is one insect on one host. For conifers the decision belongs to the program, and the state's own guidance is CAL FIRE Tree Notes #3, which prints the clocks:
To be effective, lop and scatter slash within one week of slash creation. As an alternative, avoid activities in pine stands that will place "green" slash on the ground from February through June. To be effective, the remaining techniques must be completed within five weeks of slash creation or before beetle broods emerge
One week for lop and scatter, five weeks for anything else. Chipping is named as very effective and destroys most brood present, which is the disposal route most line-clearance programs already own. Debarking, piling and burning are the others. For material held rather than chipped, the tarping spec is six mil clear plastic with 12 inches of overlap sealed along the ground, tarped for one season from April 1 until November 1. Black plastic fails, because the beetles chew through it.
Two of the timing rules collide with the working year, and they disagree with each other. CAL FIRE says avoid putting green pine slash on the ground February through June. UC IPM puts the pine pruning window outside February to mid-October. A clearance program working to a compliance date will break one window or the other. What it can do is record which one it worked to and why, treat the slash inside the five weeks, and keep the loads local.
On the plastic the two sources also differ, with CAL FIRE specifying six mil and UC IPM recommending ten mil, so a program writing a standard should name which source it followed. Slash handling and site cleanup and the seasonal restrictions already on the circuit are where these rules land in practice.
What a bark beetle record has to carry
A dead conifer file is defended on the date knowledge was acquired and on the basis for the call. A photograph of a red crown leaves both blank. The fields worth carrying:
Field | Why it is there |
Host species and diameter | Decides which beetles are plausible and how long the snag will stand |
Attack signs and the height they were seen | Pitch tubes at 4 feet and pitch tubes at 20 feet point at different insects |
Crown condition, in words | Green, fading yellow-green, or brown, rather than "dead" |
Estimated year of death and its basis | Red fir holds brown needles for years; state the evidence |
Date and source of knowledge | Patrol, detailed inspection, customer notification, or aerial layer with its vintage |
Associated agents present | Conks, mistletoe, root disease, fire scar, recent excavation near the base |
Distance and lean relative to the right-of-way | Whether 14 CCR 1104.1(e)(3) is being relied on |
Exemption number and acceptance date | Where the work is on timberland |
Disposition of the material and the date | Chipped, debarked, burned, or hauled, against the five-week clock |
Two of those rows exist only because of this subject. The estimated year of death is what converts a static inventory of snags into a queue ordered by the 5-to-15-year fall window. The date and source of knowledge is what Rule 35 is written around, and in a year when most of California went unflown, it is the row that will be hardest to fill and the one most likely to be asked about.
Further reading
Douglas-fir near power lines: height, fall zone and fire risk: The conifer whose fall zone the standing dead keep refilling, and the flatheaded fir borer that is not a bark beetle.
Pitch canker and California pines: what line-clearance crews watch for: The other California conifer agent whose regulation lands on the wood rather than on the standing tree.
Post-fire hazard trees: Where the fire-injured conifer goes next, which is into the brood material for the following spring.
Frequently asked questions
Did the end of the tree mortality emergency change what a utility has to do about dead conifers?
It changed the source of the obligation, not the obligation. The Proclamation of a State of Emergency signed October 30, 2015 ordered that "State agencies, utilities, and local governments to the extent required by their existing responsibilities to protect the public health and safety, shall undertake efforts to remove dead or dying trees in these high hazard zones that threaten power lines." Governor Newsom terminated that proclamation on March 24, 2026, and the termination states that "any Executive Order provisions related to the terminated states of emergency are no longer in effect." What is left standing is the ordinary law, principally the second paragraph of GO 95 Rule 35, which never depended on the emergency and does not mention high hazard zones.
Can a crew tell from the ground that a conifer has been attacked?
Sometimes, and the window is short. UC IPM's Pest Notes Publication 7421 says that infestation status is determined by inspecting the trunk or limbs for fresh pitch tubes or frass, peeling a small portion of outer bark, and inspecting foliage for yellow or yellow-green needles. The same publication records the more common outcome: "Frequently the infestation is diagnosed after the beetles have vacated the tree. For example, when reddish brown foliage is observed the tree is dead and the new generation of bark beetles has already emerged from the tree." A record that says "pitch tubes at 12 feet, frass in bark crevices, crown still green" is worth more than one that says "red crown."
Does cutting a beetle-killed conifer on timberland need a Timber Harvesting Plan?
Not when the work fits the utility right-of-way exemption. 14 CCR 1104.1(c) exempts clearing of trees from timberland by a private or public utility for construction of electric rights-of-way and for maintenance and repair of the utility and right-of-way, capped at the widths in the table at 1104.1(d). A single overhead electric circuit at 0 to 33 kV gets 20 feet. Subsection 1104.1(e)(3) then allows "Additional clearance for removal of Danger Trees as defined in 14 CCR § 895.1," and that definition includes a tree that is "dead or with dead top." The notice is CAL FIRE form RM-73, and no operations may be conducted until the notice of acceptance is received.
What has to happen to the wood?
No California statute reaches bark beetle wood generally. Public Resources Code section 4714.5 prohibits moving eucalyptus wood containing live eucalyptus longhorned borers or their larvae in trucks or trailers, and that is a single-species rule. For conifers, the operative guidance is CAL FIRE Tree Notes #3, which says to lop and scatter within one week of slash creation, and that the remaining treatments, which are piling and burning, chipping and debarking, "must be completed within five weeks of slash creation or before beetle broods emerge." Chipping is named as effective and is what most line-clearance programs already own.
How long does a beetle-killed conifer stand?
Long enough to be missed on one cycle and not on the next. The summary in Knapp's 2015 paper on dead wood in Sierra Nevada mixed conifer is that "Most snags remain standing 5 years after tree death but then begin to rapidly fall between the 5th and 15th years," citing Keen 1955, and that fir snags remain upright longer on average than pine. Larger diameter snags with more heartwood fall more slowly. The limbs go first, which is why the conductor usually meets the tree before the ground does.
