Fir engraver beetle

Trees affected

White fir and grand fir (the true firs)

Where in our area

Mountain communities around Lake Tahoe and the Carson Range, and firs planted in yards

Key sign

Horizontal galleries under the bark, red-brown boring dust in bark cracks, no pitch tubes

Damage

Dead tree tops, dead patches of bark, or a dead tree

Nevada 2023 survey

12,440 acres of fir engraver mortality, up from 7,616 acres in 2022

The fir engraver was the most common cause of tree mortality in Nevada's 2023 forest survey. The fir engraver (Scolytus ventralis) is a small shiny black beetle. It does the most harm to firs that are already stressed by drought, crowding or root trouble. This page covers how to recognize its damage, what an arborist checks, and when pruning or removal is the right call. Battle Born Tree Service does not spray, inject or apply products to trees. We identify the problem, prune out dead or hazardous wood and remove trees that cannot be saved.

How do you recognize fir engraver damage?

The adult beetle is about a fifth of an inch long, shiny and black, and you are unlikely to see it. What a homeowner can see is the tree. A fir that is attacked may show a top that thins and browns while the lower crown stays green, or a crown that fades all over. The Forest Service guide for the fir engraver describes attacks that kill the top of the tree, a patch of bark or the entire tree.

Look at the bark and the base of the trunk too. Fir engraver attacks leave reddish-brown boring dust in the bark crevices of larger trunks. Unlike pine beetles, the guide says the fir engraver does not make pitch tubes, so a fir with no pitch tubes is not in the clear. The clearest sign is under the bark, where the beetle's egg galleries run across the grain, horizontally, for several inches. Peeling bark off a standing tree is a job for the arborist, not the homeowner.

Which trees and which elevations?

The main hosts are white fir and grand fir. In Northern Nevada that means the true firs of the Sierra Nevada and the Carson Range, which are the forests above our mountain towns: Glenbrook (6,243 feet), Zephyr Cove (6,258), Stateline (6,284), Incline Village (6,437) and Kingsbury (7,126). White fir is also planted in yards in lower towns, though the valley floors have few firs. The beetle's hosts are true firs, so a browning pine near a fir is more likely a different problem. See bark beetles in pines and white fir.

Why do firs get attacked?

The fir engraver goes after trees that are already weak. The guide lists drought and stress as the usual setting, and dry years leave firs with less resin to fight the beetle. Roots matter as well: a fir with decaying roots or butt rot is an easy target, and the Forest Service also lists a root disease complex that damages white fir at high elevation. See root and trunk decay and drought stress and dieback.

Beetle pressure moves with the weather. Nevada's 2023 forest health report counted 12,440 acres of fir engraver mortality, up from 7,616 acres in 2022, and called it the most common agent of mortality that year. The same report said mountain pine beetle and pinyon ips fell sharply after a wet winter, but that does not mean true firs are out of danger.

What does an arborist check?

An arborist checks how much of the crown is dead, looks for boring dust to tell the fir engraver from other causes, and inspects the roots and base. They also look at nearby firs and at what is in the way of a safe removal.

• How much of the crown is dead or fading, and whether the damage is only at the top
• Boring dust and galleries, to tell the fir engraver from other causes of browning such as root rot or drought
• The condition of the roots and base, since decay there changes the plan
• Other firs nearby, and whether a dead or dying fir leans over a house, driveway, play area or road
• What is in the way of a safe removal, such as wires, a roof or a steep slope

When is pruning or removal the answer?

If only the top of a fir has died and the rest of the crown is healthy, an arborist may take out the dead top and dead limbs and watch the tree. See dead wooding. If the whole crown has faded, the tree is dead and removal is the usual step. Dead firs become brittle, so do not wait for a windstorm to decide. A dead fir near a house or a power line is a job for a crew with the right equipment, and for some trees that means crane-assisted removal.

In the Tahoe Basin, a dead tree that could fall on a house does not need a TRPA permit, but a live tree over 14 inches in diameter does, and the agency decides. See the Tahoe 14 inch rule. If any part of the tree is in a power line, stay away and call NV Energy. If anyone is hurt, call 911. For anything else, call 775.232.8243 and we will schedule a consultation with an ISA Certified Arborist.