Bark beetles in pines and firs

Bark beetle profiles

Pine Bark Beetles Dendroctonus frontalis and Ips species (I. calligraphus, I. grandicollis, I. avulsus) Pine bark beetles are tiny beetles that breed in the inner bark of pines. The southern pine beetle and three Ips engraver beetles are the main tree-killing species in the Southeast, and once beetles successfully colonize a pine, the tree can't be saved. Pine Engraver Ips pini The pine engraver is a small bark beetle that breeds in freshly cut pine material and attacks stressed or newly planted pines, killing tops or whole trees; it almost never attacks healthy pines in years with normal rainfall. No photo yet Western Pine Beetle Dendroctonus brevicomis The western pine beetle is a native bark beetle that attacks the trunks of ponderosa pines, killing trees weakened by drought, fire, disease or crowding, often in groups. Douglas-fir Beetle Dendroctonus pseudotsugae The Douglas-fir beetle is a native bark beetle that breeds in windthrown, fire-scorched or weakened Douglas-firs; when downed or damaged trees are plentiful, populations build and spill over into healthy trees, killing them in groups. Mountain Pine Beetle Dendroctonus ponderosae Mountain pine beetle is a native bark beetle of western North America whose outbreaks can kill millions of pines. Red Turpentine Beetle Dendroctonus valens Red turpentine beetles attack the lower trunk of pines, even near the root collar and below ground. Black Turpentine Beetle Dendroctonus terebrans Reddish pitch tubes on the lower few feet of a pine trunk often mean black turpentine beetles; numerous attacks can kill the tree. Spruce Beetle Dendroctonus rufipennis The spruce beetle is a native bark beetle and a major cause of spruce death in North America, especially in Alaska and the Rocky Mountains.

Signs of a bark beetle attack

Look for yellow, orange or reddish-brown boring dust in the bark crevices and at the base of the tree, small shot-hole exit holes in the bark, and needles turning yellow to red.^[3]

• Woodpeckers flaking off the outer bark to reach the larvae is a common sign on ponderosa pines attacked by western pine beetle.^[5]
• Pitch streamers on the trunk can also mark an attack; Douglas-fir beetle attacks are often most plentiful midway up the trunk.^[8]

Telling the beetles apart by their tunnels

Peeling back a piece of bark from a dying tree shows the gallery pattern, which differs by species.^[5][7]

• Pine engravers (Ips beetles) leave branching tunnels etched into the inner bark and often attack the tops of trees or small material.^[3][1][4]
• Western pine beetles cut winding, criss-crossing galleries in ponderosa pine.^[5]
• Douglas-fir beetles lay eggs in niches alternating on opposite sides of a gallery that runs along the trunk.^[7]

Which trees are at risk

Newly planted trees and trees stressed by drought, root injury, soil compaction or disease are attacked first; during outbreaks the beetles can kill healthier trees too.^[1][2][5]

• Pine engraver populations build in fresh pine slash and cut material and then move into nearby standing pines.^[2][4]
• Douglas-fir beetles breed in windthrown or fire-damaged Douglas-firs and attack standing trees a year or two later.^[6]

Protecting landscape trees

Prevention works far better than treatment, because a tree that bark beetles have colonized usually can't be saved.^[1][3]

• Water trees during drought and avoid root injury and soil compaction.^[1]
• Don't leave fresh pine slash or firewood near live pines through spring and summer, and remove infested trees before new beetles emerge.^[2][5]
• Thin crowded stands of pine and Douglas-fir to keep the remaining trees vigorous.^[5][6]
• Preventive trunk sprays on valuable trees, or MCH repellent pouches for Douglas-fir, must go on before the beetles fly in spring.^[5][3][6]

Common questions

Can a tree with bark beetles be saved?

Usually not once the beetles are established; removing it promptly protects nearby trees.^[3][5]

Why do bark beetles attack my pines after a drought?

Outbreaks usually build in trees weakened by drought, fire, root disease, soil compaction or crowding.^[5]

Sources

1. Colorado State University Extension, “Ips Beetles (Fact Sheet 5.558, W. Cranshaw; copy hosted by Utah State University).” extension.usu.edu/pests/uppdl/files/factsheet/05558.pdf (accessed 2026-10-17)
2. Wisconsin DNR Forest Health Protection (hosted by UW Forestry Extension), “The Pine Engraver Bark Beetle (Ips pini) in Northern Wisconsin (FHP-2).” forestry.extension.wisc.edu/files/2017/09/FHP-2.pdf (accessed 2026-10-17)
3. Montana State University Extension (Urban IPM), “Engraver Beetles (Ips spp.).” urbanipm.montana.edu/entomology/resources/fact-sheets/engraver-beetles.html (accessed 2026-10-17)
4. Oregon Department of Forestry, “Ips beetles (Forest Health Fact Sheet).” oregon.gov/odf/documents/forestbenefits/ips.pdf (accessed 2026-10-17)
5. Oregon Department of Forestry, “Western Pine Beetle (Forest Health Fact Sheet, March 2017).” egov.oregon.gov/odf/Documents/forestbenefits/Western%20Pine%20Beetle.pdf (accessed 2026-10-17)
6. Idaho Department of Lands, “Douglas-fir Beetle (Forest Pest Fact Sheet, 2020).” www.idl.idaho.gov/wp-content/uploads/sites/2/2020/03/2016-single-pest-fact-sheet-Douglas-fir-Beetle_3_19_2020.pdf (accessed 2026-10-17)
7. USDA Forest Service, “Douglas-fir Beetle (Forest Insect & Disease Leaflet 5, rev. February 2014; M. M. Furniss and S. J. Kegley; copy hosted by Montana DNRC).” dnrc.mt.gov/_docs/forestry/Forestry_Assistance/Forest_Pests/Douglas-firBeetle-FIDL.pdf (accessed 2026-10-17)
8. USDA Forest Service (DecAID), “Douglas-Fir Beetle (DecAID Advisor species account).” apps.fs.usda.gov/decaid/views/douglas_fir_beetle.html (accessed 2026-10-17)