Northern spruce engraver

How to identify it

• Adults are small, 4.0 to 4.8 mm long, cylindrical and reddish-brown to black, with four spines along the outer margin of the concave rear end of the wing covers. The third spine is conical with an acute tip, shaped like the ace of spades, which separates this beetle from other boreal Ips species; it is also typically larger and wider than they are.^[1]
• Spruce beetle is the main confusion. Spruce beetles are larger, 4.4 to 7.0 mm, with evenly rounded wing covers that have no spines, and their head is visible from above; the engraver's is not.^[1]
• Under the bark the egg galleries form a tuning-fork or Y shape and are kept clear of frass by the parent beetles, often etched onto the surface of the wood. Spruce beetle galleries can be partly blocked with frass.^[1]
• The first external sign is reddish-brown boring dust at the entrance holes, in bark crevices and on the ground around the trunk, usually in distinct piles that mark individual holes. Unsuccessful attacks with pitch are rarely seen, unlike with spruce beetle, and on windthrown trees and log decks engraver entrance holes are more often on the upper surfaces while spruce beetle attacks are underneath.^[1]

Look-alikes

Where it lives

Boreal and sub-boreal forests of North America, with a range that generally follows its main host, white spruce. The beetle has been recorded from Alaska, Maine, Michigan, Minnesota, Montana and Washington and from nearly all Canadian provinces; other hosts are Engelmann spruce, Lutz spruce and, rarely, black or Sitka spruce.^[1]

US map: public records from 2 states since 1990 (GBIF). View the map

Biology and life cycle

Males start the gallery in the phloem and are joined by up to four females in a central nuptial chamber. The mated females extend the arms of the tuning fork and lay about 50 eggs each in individual niches along the walls.^[1]

Eggs are oblong, pearly white and under 1.5 mm; larvae hatch in 7 to 10 days, feed on phloem through four instars and reach about 3.3 mm, pupate after 4 to 5 weeks, and spend about 10 days as pupae. New adults usually leave the tree before winter, most staying under the bark a few weeks first, then dropping to the ground to overwinter in the litter beneath the brood tree.^[1]

There is normally one generation a year throughout the range. Adults begin flying from overwintering sites in late April to late May in both Alaska and Minnesota and continue to mid-July, with peak flight in early to mid-June, once daytime temperatures pass about 62 degrees F. Most fly only about 100 feet, though some have been recorded moving up to a quarter mile. In Alaska adults establish a single gallery system in a brood tree and do not re-emerge to attack again.^[1]

Production from a single tree can be large: in eastern Canada, 2,000 mated pairs produced as many as 22,000 beetles from a 48-foot section of infested white spruce, and gallery density in Alberta white spruce averaged 20 breeding galleries per square foot of bark.^[1]

The beetles carry bluestain fungi that may also harm the tree. A University of British Columbia survey of beetles and galleries from felled spruce and logs in northern British Columbia and the Yukon identified 13 ophiostomatoid fungal species, among them Leptographium fruticetum, L. abietinum, Ophiostoma bicolor, O. manitobense and O. piceaperdum plus eight undescribed species; L. fruticetum, described as a new species from this beetle, was the most dominant and was isolated repeatedly, which the authors suggest may indicate a specific relationship with the beetle.^[1][2][3]

Damage and signs

• Adults colonize the stems and larger branches of standing trees and are also frequently found in fallen trees, slash from harvest and thinning, and storm-broken debris more than 2 to 3 inches in diameter. Larval mining kills the phloem and outer xylem, which tops large trees and kills small ones outright.^[1]
• Needles fade from dark green through pale yellowish-green to red as early as a month after attack, by July in interior Alaska, and most foliage has faded and dropped by the end of the first summer. That is faster than spruce beetle, whose killed trees usually do not discolor until the following year.^[1]
• Outbreaks follow disturbance: wildfire, wind and ice storms, heavy snow, river flooding, bank erosion, road and house building, utility rights-of-way and logging all leave breeding material. Water stress and dense stands raise susceptibility, older stands are less able to defend themselves, and during intense outbreaks even spruce 1 to 2 inches in diameter are attacked and killed. Trees with up to 60 percent of their circumference girdled by porcupines still repelled attacks, but above that mortality went up.^[1]
• Large outbreaks change the stand: removing the canopy can increase understory diversity and leave a fuel complex of big dead wood and flammable dry grasses such as bluejoint reedgrass. Wildlife that needs live mature spruce, including Townsend's warbler, ruby-crowned kinglet, spruce grouse and red and flying squirrels, may be affected negatively, while moose and other early-successional species may benefit.^[1]

Health risk

A forest insect with no reported effect on people; the leaflet describes damage to spruce only.^[1]

Control

Prevention

The main preventive strategy is thinning followed by proper slash management, aimed at keeping stands healthy and growing at a moderate rate. Suppression measures are short-term responses, so vulnerable sites should be re-inspected for new activity rather than treated once and forgotten.^[1]

During harvest or thinning, minimize mechanical damage to the trees you are keeping, practice good logging sanitation and limit soil compaction and disturbance around the root zones of residual spruce.^[1]

Sanitation

Handle the slash. Only spruce slash under 4 inches in diameter can be left untreated, because it produces far fewer beetles than larger pieces; cull logs and tops should be limbed, cut into short lengths and exposed to sunlight, and scoring larger pieces with a chain saw promotes phloem drying though it is costly. As a general rule, anything that dries and ages the phloem faster helps. Keep firewood piles and slash decks away from live trees.^[1]

Traps and physical control

Prescribed fire in late summer and early fall, already used in interior Alaska for fuels reduction and wildlife habitat, can also destroy adults overwintering in the litter. Solar heating of slash piles and decked logs under heavy plastic sheeting, used for bark beetles in the western United States, has not been shown to work in Alaska.^[1]

Pesticides

Males produce an aggregation pheromone of ipsenol, ipsdienol and cis-verbenol that draws in both sexes; synthetic versions are sold and have been used as trap baits for mass trapping and monitoring, with moderate success in trap-out operations during interior Alaska fuels projects in the early 2000s. These compounds are not EPA registered for direct application, though behavioral chemicals used in traps need no registration and can be used in consultation with forest health professionals. A behavioral interruptant combining trans-conophthorin and verbenone has protected individual spruce in Alaska and may be worth the cost for high-value trees in yards, campgrounds and administrative sites.^[1]

For high-value uninfested spruce, bole sprays of carbaryl or permethrin applied with a hydraulic sprayer above 325 psi kill attacking beetles; 2 percent carbaryl protected individual trees from engravers and spruce beetles for at least two years. These preventive treatments go on from late fall to late April, before dispersal flight, usually spraying to runoff up to about 40 feet. Check current registrations with a county agricultural agent or state extension specialist.^[1]

Related profiles

• Spruce Beetle
• Pine Engraver
• Eastern larch beetle
• Pine Sawyers

Common questions

How do I tell this from spruce beetle?

Size, spines and gallery. The engraver is 4.0 to 4.8 mm with four spines on each side of the concave rear and a head hidden from above; spruce beetle is 4.4 to 7.0 mm, has evenly rounded, spineless wing covers and a visible head. Engraver galleries are tuning-fork shaped and free of frass, and its killed trees fade within the first summer rather than the next year.^[1]

Will leaving my thinning slash cause an outbreak?

Slash is the main breeding material. Pieces under 4 inches in diameter produce far fewer beetles and can be left, but larger cull logs and tops should be limbed, cut short and exposed to sun so the phloem dries, and slash decks and firewood piles should not sit next to live spruce.^[1]

Can I protect a single high-value spruce?

Yes, two ways. A trans-conophthorin and verbenone interruptant has protected individual trees in Alaska, and a bole spray of carbaryl or permethrin applied before the spring flight protects trees for a season or more, with 2 percent carbaryl giving at least two years in trials.^[1]

Sources

1. USDA Forest Service, Pacific Northwest Region, Forest Health Protection, “Forest Insect & Disease Leaflet 180: Northern Spruce Engraver (Burnside, Holsten, Fettig, Kruse, Schultz, Hayes, Graves and Seybold, September 2011).” www.fs.usda.gov/foresthealth/docs/fidls/FIDL-180-NorthernSpruceEngraver.pdf (accessed 2026-11-10)
2. Antonie van Leeuwenhoek (Springer), “Massoumi Alamouti, Kim, Humble, Uzunovic and Breuil (University of British Columbia). Ophiostomatoid fungi associated with the northern spruce engraver, Ips perturbatus, in western Canada. Antonie van Leeuwenhoek 91 (2007) 19-34, PMID 17066342.” pubmed.ncbi.nlm.nih.gov/17066342/ (accessed 2026-11-10)
3. Mycologia (Mycological Society of America), “Massoumi Alamouti, Kim and Breuil (University of British Columbia). A new Leptographium species associated with the northern spruce engraver, Ips perturbatus, in western Canada. Mycologia 98 (2006) 149-160, PMID 16800314.” pubmed.ncbi.nlm.nih.gov/16800314/ (accessed 2026-11-10)
4. iNaturalist, “Ips perturbatus taxon page (order and family).” www.inaturalist.org/taxa/222276 (accessed 2026-11-10)