Forest & Grassland Health

Northern Spruce Engraver & Other Ips spp.

Ips perturbatus (Eichhoff), 
I. tridens (Mannerheim), I. borealis Swaine, I. pini (Say), Pseudips concinnus (Mannerheim), P. mexicanus (LeConte) 

Host(s) of Ips perturbatus in Alaska:

White spruce (Piceae glauca), black spruce (P. mariana),  Lutz spruce (P. glauca x sitchensis), and Sitka spruce (P. sitchensis)

Habitat(s): phloem, inner bark, and bark

Damage: Beetle larvae feeding in phloem tissue can girdle trees, resulting in tree mortality.

Photos

Click on image for larger version.

High resolution photograph of Ips perturbatus in lateral view

I. perturbatus, lateral view.

High magnification photograph of the declivital spines on male Ips perturbatus specimen

I. perturbatus male, declivital spines, lateral view.

A photo of Ips sp. galleries with three adult Ips beetles and empty egg chambers

 Ips sp. larval galleries.

Photograph of an Ips sp. gallery with larvae in the egg chambers

Ips sp. larval galleries.

A lateral view of an Ips sp. specimen imagedby scanning electron microscope.

SEM image of I. perturbatus, oblique view.

Current Status (2020 Update)

No notable areas of northern spruce engraver damage were observed during the 2020 ground surveys or imagery interpretation efforts. Damage from northern spruce engraver is typically mapped along streams and rivers and in areas with natural disturbances such as fire and wind.  Ips spp. were responsible for 1,071 acres of damage in 2019.

Historic Activity

High populations of engraver beetles caused white spruce mortality on 43,000 acres along the south side of the Brooks Range, and in the McGrath area, in 2008. High populations are common in river-bottom spruce stands of interior Alaska, particularly those periodically flooded along the Yukon, Porcupine, Chandalar, and Tanana Rivers. 

Symptoms, Biology, & Impacts 

Adult engraver beetles are small (3.0 to 4.9 mm long), cylindrical, reddish-brown to black beetles who have a distinct declivity (concave area) on their posterior end with 3 to 4 pairs of tooth-like spines along the outer margins. Species of engraver beetle are differentiated mainly by those spines. Engraver beetles normally completes its life cycle in one year throughout its range, although some observations suggested that the adult stage may last nearly two years while some species can have two generations per year. Adults overwinter as adults primarily in forest litter beneath their brood trees, though occasionally under the bark of the host material in which they developed depending on species. In Alaska, adults begin flying from overwintering sites in late April to late May and continue to mid-July, with peak flight in early to mid-June. The exact timing of emergence depends on temperature. Dispersing beetles attack fresh host materials soon after emergence. Galleries are initiated in the phloem by males, which are later joined by and mate with up to four females in a central nuptial chamber. Mated females extend egg galleries (the arms of the “tuning fork”) that radiate from the central nuptial chamber and deposit eggs in individual niches along the gallery walls. Eggs are oblong, pearly white, and less than 1.5 mm long. Larvae hatch from eggs in 7 to 10 days and feed on phloem tissue. These larvae are stout, cylindrical, legless grubs that pass through four instars (stages) and reach a length of about 3.3 mm at maturity. They develop into pupae after 4 to 5 weeks. Pupae are opaque white, inactive, and somewhat similar in size and shape to adults. The pupal stage lasts approximately 10 days. Pupae transform to new adults and usually exit the host material before the onset of winter. In most cases new adults remain under the bark of the infested tree for a few weeks before moving to their overwinter location. In Alaska, adults have been observed to only establish a single gallery system in a brood tree; adults do not re-emerge and reattack the same or neighboring trees or host logs. Large diameter infested spruce can produce enormous quantities of new adults.  

These beetles are known for their opportunistic use of trees damaged by fire, drought, flooding, and human development activities that alter forest stands. The first evidence of engraver beetle attack is the presence of fine, yellow-red boring dust in bark crevices. Preferred host material includes freshly cut logs, and tops of weakened trees. Trees with dead and dying tops are evidence of engraver beetle damage and mortality. 

At first glance, engraver beetles may be confused with spruce beetle (Dendroctonus rufipennis). However, spruce beetles are larger (about 4.4 to 7.0 mm long) with its head visible when viewed from above and elytra (wing covers) that are evenly rounded, without spines along the elytral declivity. Engraver egg galleries are also kept free of frass by parent adults unlike spruce beetle galleries that can be partially blocked with frass. Unlike spruce beetle damage and injury, pitch-tubes are rarely formed in response to engraver beetle infestations. 

Guidelines for Reducing Damage 

Direct control operations generally are not used against Ips as outbreaks develop and disappear rapidly, usually within three years. To reduce engraver beetle population buildup and damage, maintain healthy spruce stands. This can be accomplished by removal of over-mature, densely grown, diseased, and dying trees. Damaged and windthrown trees should be removed or used or destroyed by cutting, burning, chipping, or burying. Partially burned trees in the fringe area of a wildfire should be harvested immediately after the fire if the fire occurs in early spring; otherwise, harvest during the late summer, fall or winter. Timber harvests should be scheduled after July and before February. This ensures that all breeding material produced during the harvest is at least three months old by the time of the beetles flight, rendering it less suitable then fresh material. Infested wood should not be stacked or stored in areas surrounded by live trees. Freshly cut spruce should have the bark removed and/ or be spilt for rapid drying as soon as possible following harvest. Cull logs, tops, and slash greater than 4 inches in diameter should be limbed and cut into short lengths. The material should then be processed or stacked. Insecticides can be used to protect high-value trees from beetle attack.  

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Western Ips spp. with Host, Distribution & Impacts

Species Name

Hosts

Common Name

Distribution

Impacts

Ips 
perturbatus 

(Eichhoff) 

Picea glauca,
P.  engelmannii,
P. lutzii
(P. glauca x sitchensis)
Rarely:
P. mariana,
P. sitchensis

Northern spruce engraver

Throughout Interior, SC, and SE Alaska

Breeds in logged, slashed, and windthrown trees; overwinters as adults in leaf litter underneath their brood trees

I. tridens 
(Mannerheim) 

Picea engelmannii,
P. glauca, 
P. sitchensis

 -

Interior, SC, and SE AK, including the Kenai Peninsula.

Attacks weakened and downed trees

I. borealis
Swaine 

P. glauca,
P.
x lutzii, 
P. engelmannii

 -

Interior & SC, AK, including the Kenai Peninsula.

Associated with I. perturbatus in white spruce, with narrower egg galleries

I. pini 
(Say) 

Pinus ponderosa,
P. contorta,
P. flexilis,
P. jeffreyi,

other Pinus spp.
also Piceae

Pine engraver

SE AK (Douglas Is., Ketchikan)

Attacks windfallen trees, recently cut logs, and slash; 1-5 generations per year, depending on locality and season length

Pseudips (=Ips)
concinnus

(Mannerheim) 

P. sitchensis,
P. × lutzii

Sitka spruce “Ips”

 SC & SE AK, Kodiak Is.

Attacks injured, dying, and downed Sitka spruce

Pseudips (=Ips) 
mexicanus 
(Hopkins) 

 

Pinus contorta,
P. radiata,
P. albicaulis,
P. attenuata,
P. flexilis,
P. muricata,

other Pinus spp.

Monterey pine “Ips”

 SE AK (Juneau, Douglas Is.)

Commonly associated with other bark beetle species; attacks living, injured, dying, and downed pines

Table References: Burnside et al. 2011, Furniss et al. 2002, Graves et al. 2008
https://www.barkbeetles.org/ips/Westips.html


Resources and Publications 

Burnside, R. E., Holsten, E. H., Fettig, C. J., Kruse, J. J. Schultz, M. E., Hayes, C. J., Graves, A. D., and S. J. Seybold. 2011. Northern Spruce Engraver Forest Insect and Disease Leaflet. FIDL-180. Available here

Furniss, M. M., Holsten, E. H., Schultz, M. E. 2002. Species of Alaska Scolytidae: Distribution, hosts, and historical review. Entomological Society of British Columbia, 99: 83-92.

Graves, A. D., Holsten, E. H., Ascerno, M. E., Zogas, K. P., Hard, J. S., Huber, D. P., ... & Seybold, S. J. 2008. Protection of spruce from colonization by the bark beetle, Ips perturbatus, in Alaska. Forest ecology and management256(11): 1825-1839.

Holsten, E. H. 2013. Engraver Beetles in Alaska. USDA Forest Service, Alaska Region, State and Private Forestry. Leaflet R10-TP-155. Available here or here

Holsten, E. H., Hennon, P., Trummer, L., Kruse, J., Schultz, M., & Lundquist, J. 2008. Insects and Diseases of Alaskan Forests. USDA Forest Service, Alaska Region, State and Private Forestry, Forest Health Protection. Publication R10-TP-140, 55. Available here.  

 

Content adapted from Insects and Diseases of Alaskan Forests (2008) p.78-80 (available here) and Engraver Beetles in Alaska Forest Health Leaflet (available here or here). 

For more information about this agent, contact Entomologist Dr. Sydney Brannoch at sydney.brannoch@usda.gov. Content prepared by Dana Brennan, Biological Science Technician.

 

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