Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Datasheet

Dendroctonus rufipennis
(spruce beetle)

Toolbox

Datasheet

Dendroctonus rufipennis (spruce beetle)

Pictures

Top of page
PictureTitleCaptionCopyright
Tree mortality in Engelmann spruce, caused by D. rufipennis, in Wallowa-Whitman National Forest, Oregon, USA.
TitleDamaged stand
CaptionTree mortality in Engelmann spruce, caused by D. rufipennis, in Wallowa-Whitman National Forest, Oregon, USA.
CopyrightWilliam M. Ciesla
Tree mortality in Engelmann spruce, caused by D. rufipennis, in Wallowa-Whitman National Forest, Oregon, USA.
Damaged standTree mortality in Engelmann spruce, caused by D. rufipennis, in Wallowa-Whitman National Forest, Oregon, USA.William M. Ciesla
Aerial view of mortality of Picea glauca caused by D. rufipennis. Kenai Peninsula, Alaska, USA.
TitleAerial view of mortality
CaptionAerial view of mortality of Picea glauca caused by D. rufipennis. Kenai Peninsula, Alaska, USA.
CopyrightWilliam M. Ciesla
Aerial view of mortality of Picea glauca caused by D. rufipennis. Kenai Peninsula, Alaska, USA.
Aerial view of mortalityAerial view of mortality of Picea glauca caused by D. rufipennis. Kenai Peninsula, Alaska, USA.William M. Ciesla
D. rufipennis adult.
TitleAdult
CaptionD. rufipennis adult.
CopyrightWilliam M. Ciesla
D. rufipennis adult.
AdultD. rufipennis adult.William M. Ciesla

Identity

Top of page

Preferred Scientific Name

  • Dendroctonus rufipennis (Kirby, 1837)

Preferred Common Name

  • spruce beetle

Other Scientific Names

  • Dendroctonus borealis Hopkins, 1909
  • Dendroctonus engelmanni Hopkins, 1909
  • Dendroctonus obesus (Mannerheim, 1843)
  • Dendroctonus piceaperda Hopkins, 1901
  • Dendroctonus similis LeConte, 1857
  • Hylurgus obesus Mannerheim, 1843
  • Hylurgus rufipennis Kirby, 1837

International Common Names

  • English: Alaska spruce beetle; beetle, Alaska spruce; beetle, eastern spruce; beetle, Engelmann spruce; beetle, red-winged pine; beetle, sitka-spruce; beetle, spruce; eastern spruce beetle; Engelmann spruce beetle; spruce bark beetle
  • French: dendroctone d' Engelmann; dendroctone de l'épinette; dendroctone de l'epinette sitka

Local Common Names

  • Germany: Riesenbastkaefer, Sitkafichten-; Sitkafichten Riesenbastkäfer

EPPO code

  • DENCRU (Dendroctonus rufipennis)

Taxonomic Tree

Top of page
  • Domain: Eukaryota
  •     Kingdom: Metazoa
  •         Phylum: Arthropoda
  •             Subphylum: Uniramia
  •                 Class: Insecta
  •                     Order: Coleoptera
  •                         Family: Scolytidae
  •                             Genus: Dendroctonus
  •                                 Species: Dendroctonus rufipennis

Notes on Taxonomy and Nomenclature

Top of page This insect was originally described as Hylurgus rufipennis by Kirby in 1837. J.L. LeConte placed it in the genus Dendroctonus in 1868. Prior to 1963, six species of spruce inhabiting Dendroctonus were recognized in North America. Wood (1963) synonymized these species under the name D. obesus. However, D. rufipennis (Kirby) was an older name and had priority. Wood corrected this oversight in 1969 and established D. rufipennis as the proper name (Schmid and Frye, 1977).

Description

Top of page Eggs

Eggs of beetles of the family Scolytidae are smooth, ovoid, white and translucent. Spruce beetle eggs (1-2 mm long) are deposited in short rows along both sides of the egg gallery at a rate of between 4 and 14 eggs per centimetre of gallery (Holsten et al., 1989).

Larvae

The larval stages of insects of the family Scolytidae are all similar in appearance and difficult to separate. They are white, 'c'-shaped, legless grubs. The head capsule is lightly sclerotized, amber in colour with dark, well-developed mouthparts. The abdominal segments each have two or three tergal folds and the pleuron is not longitudinally divided. The larvae do not change as they grow. Spruce beetle beetle larvae pass through four larval instars and are 4-6 mm long when mature (Holsten et al., 1989).

Pupae

Scolytid pupae are white and mummy-like. They are exarate, with legs and wings free from the body. Some species have paired abdominal urogomphi. The elytra are either rugose or smooth, sometimes with prominent head and thoracic tubercles.

Adults

Adults are blackish-brown to black with reddish-brown or black elytra. They are cylindrical and range in length from 3.4 to 5.0 mm (average 4.2 mm) long and about 3 mm wide. The elytra are 2.5 times the length of the pronontum (Wood, 1982; Holsten et al., 1989).

Distribution

Top of page

D. rufipennis is found throughout the range of spruce in North America, from eastern Canada, south along the Appalachian Mountains, west across the boreal forests of Canada and Alaska and south along crests of the Rocky Mountains and Cascades to northern California, Arizona and New Mexico (see map in Holsten et al., 1989).

See also CABI/EPPO (1998, No. 61).

Distribution Table

Top of page

The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

Continent/Country/RegionDistributionLast ReportedOriginFirst ReportedInvasiveReferenceNotes

Africa

South AfricaAbsent, invalid recordCABI/EPPO, 2004; EPPO, 2014

North America

CanadaWidespreadCABI/EPPO, 2004; EPPO, 2014
-AlbertaWidespreadNative Invasive Wood, 1982; CABI/EPPO, 2004; EPPO, 2014
-British ColumbiaWidespreadNative Invasive Schmid and Frye, 1977; Wood, 1982; CABI/EPPO, 2004; EPPO, 2014
-ManitobaWidespreadNative Invasive Wood, 1982; CABI/EPPO, 2004; EPPO, 2014
-New BrunswickWidespreadNative Invasive Wood, 1982; CABI/EPPO, 2004; EPPO, 2014
-Newfoundland and LabradorWidespreadCABI/EPPO, 2004; EPPO, 2014
-Northwest TerritoriesWidespreadNative Invasive Wood, 1982; CABI/EPPO, 2004; EPPO, 2014
-Nova ScotiaWidespreadNative Invasive Wood, 1982; CABI/EPPO, 2004; EPPO, 2014
-NunavutWidespreadNative Invasive Wood, 1982; CABI/EPPO, 2004
-OntarioWidespreadNative Invasive Wood, 1982; CABI/EPPO, 2004; EPPO, 2014
-Prince Edward IslandPresentEPPO, 2014
-QuebecWidespreadCABI/EPPO, 2004; EPPO, 2014
-SaskatchewanWidespreadCABI/EPPO, 2004; EPPO, 2014
-Yukon TerritoryWidespreadNative Invasive Wood, 1982; CABI/EPPO, 2004; EPPO, 2014
MexicoAbsent, unreliable recordEPPO, 2014A record for Mexico in CABI/EPPO (1997) is now considered erroneous.
USAWidespreadCABI/EPPO, 2004; EPPO, 2014
-AlaskaWidespreadNative Invasive Wood, 1982; Ciesla and Coulston, 2002; CABI/EPPO, 2004; EPPO, 2014
-ArizonaWidespreadNative Invasive Schmid and Frye, 1977; Wood, 1982; CABI/EPPO, 2004; EPPO, 2014
-CaliforniaWidespreadNative Invasive Wood, 1982; CABI/EPPO, 2004; EPPO, 2014
-ColoradoWidespreadNative Invasive Schmid and Frye, 1977; Wood, 1982; Ciesla and Coulston, 2002; CABI/EPPO, 2004; EPPO, 2014
-IdahoWidespreadNative Invasive Wood, 1982; CABI/EPPO, 2004; EPPO, 2014
-MaineWidespreadNative Invasive Wood, 1982; Weiss et al., 1985; CABI/EPPO, 2004; EPPO, 2014
-MichiganWidespreadNative Invasive Wood, 1982; CABI/EPPO, 2004; EPPO, 2014
-MinnesotaWidespreadNative Invasive Wood, 1982; CABI/EPPO, 2004; EPPO, 2014
-MontanaWidespreadNative Invasive Wood, 1982; CABI/EPPO, 2004; EPPO, 2014
-NevadaWidespreadNative Invasive Wood, 1982; Weiss et al., 1985; CABI/EPPO, 2004; EPPO, 2014
-New HampshireWidespreadCABI/EPPO, 2004; EPPO, 2014
-New MexicoWidespreadNative Invasive Schmid and Frye, 1977; Wood, 1982; CABI/EPPO, 2004; EPPO, 2014
-New YorkWidespreadNative Invasive Schmid and Frye, 1977; Wood, 1982; CABI/EPPO, 2004; EPPO, 2014
-OregonWidespreadNative Invasive Wood, 1982; Ciesla and Coulston, 2002; CABI/EPPO, 2004; EPPO, 2014
-PennsylvaniaWidespreadNative Not invasive Wood, 1982; CABI/EPPO, 2004; EPPO, 2014
-South DakotaWidespreadCABI/EPPO, 2004; EPPO, 2014
-UtahWidespreadNative Invasive Schmid and Frye, 1977; Wood, 1982; CABI/EPPO, 2004; EPPO, 2014
-VermontWidespreadNative Invasive Wood, 1982; Weiss et al., 1985; CABI/EPPO, 2004; EPPO, 2014
-WashingtonWidespreadNative Invasive Wood, 1982; Ciesla and Coulston, 2002; CABI/EPPO, 2004; EPPO, 2014
-WisconsinWidespreadCABI/EPPO, 2004; EPPO, 2014
-WyomingWidespreadNative Invasive Schmid and Frye, 1977; Wood, 1982; Ciesla and Coulston, 2002; CABI/EPPO, 2004; EPPO, 2014

Risk of Introduction

Top of page Adult spruce beetles are relatively strong fliers and can fly at least 2-3 km in search of new hosts. In addition, their small size makes them subject to dispersal by air currents. Other life stages are confined to the cambium layer and inner bark and are not subject to natural dispersal.

Pathways for human-assisted dispersal include transport of unprocessed pine logs or lumber, crates, pallets and dunnage containing bark strips. It is conceivable that larvae, pupae and overwintering adults could survive an ocean voyage and be introduced into a new location. Should this new location have spruce forests, it could become established and cause severe damage. A related North American species of Dendroctonus, the red turpentine beetle (D. valens) has recently been introduced and established in China and has killed more than 6 million pines in recent years (Sun et al., 2003).

Habitat

Top of page Populations of D. rufipennis typically develop in windthrown trees and large numbers of emerging brood adults attack standing trees. Outbreaks typically occur in mature spruce forests.

Hosts/Species Affected

Top of page D. rufipennis attacks all species of spruce (Picea spp.) within its geographic range (Holsten et al., 1989). In eastern North America, red spruce (Picea rubens) is attacked. Across the transcontinental boreal forests, white spruce (Picea glauca) is attacked. In the Rocky Mountains, Engelmann spruce (Picea engelmannii) is the primary host. In the Pacific Northwest and coastal regions of Alaska, Sitka spruce (Picea sitchensis) and Lutz spruce (Picea x lutzii [Picea lutzii]), a naturally occurring hybrid of P. glauca and P. sitchensis, are attacked.

Normally D. rufipennis does not attack Picea mariana (black spruce). However, in outbreak situations, black spruce trees as small as 2 inches in diameter at breast height have been successfully attacked (Holsten E, USDA Forest Service, Alaska, personal communication, 2004).

Host Plants and Other Plants Affected

Top of page

Growth Stages

Top of page Vegetative growing stage

Symptoms

Top of page Trees attacked by spruce beetle are killed. However, the needles of spruces do not fade or discolour during the first year of attack. During the second summer following attack, most needles turn a yellowish colour. The needles on different branches of the same tree may discolour at different times. Needles are readily washed from dead trees by thunderstorms, leaving the upper crowns of exposed twigs with a yellow-orange to reddish hue.

On standing trees, the most conspicuous evidence of attack is the presence of reddish-brown sawdust in the bark crevices on the bole and around the base of infested trees. Less noticeable evidence of attack includes entrance holes without sawdust and sawdust-clogged entrance holes. Masses of resin may accumulate around the entrance holes. These symptoms are most visible in the summer following attack and become less noticeable later in the year.

Sawdust in bark crevices and on the ground directly below the stems is a sign of infestation on windthrown trees and residual trees from harvesting operations. Spruce beetles are most common on the lower surfaces of fallen trees.

During the first autumn and winter following attack, trees are typically debarked by woodpeckers in search of larvae.

The removal of the bark of infested trees should reveal egg and larval galleries and life stages of the spruce beetle (Holsten et al., 1989).

List of Symptoms/Signs

Top of page
SignLife StagesType
Leaves / yellowed or dead
Stems / gummosis or resinosis
Stems / necrosis
Stems / visible frass
Whole plant / frass visible
Whole plant / plant dead; dieback

Biology and Ecology

Top of page Life History and Habits

The genus Dendroctonus consists of 19 species worldwide. Most occur on conifers in North and Central America. Two species: Dendroctonus armandi, native to China, and D. micans are found in Palearctic conifer forests (Wood, 1982). Several species are important forest pests, capable of reaching epidemic levels and killing thousand of trees. The genus Dendroctonus contains some of the most destructive forest insects in North and Central America.

In the Rocky Mountains, a generation of spruce beetle typically requires 2 years to complete. However, they can complete a generation in 1 year on warm sites at low altitudes or may require 3 years in cool, shaded locations on north-facing slopes. Two-year cycle spruce beetles may emerge between May and October, depending on local temperature. They attack soon after emergence. Adults emerging from August to October may represent a re-emergence of parent adults or the movement of maturing brood adults to overwintering sites.

Females bore through the outer bark and, after attracting a male and mating, construct egg galleries in the cambium layer and inner bark. Egg galleries are slightly wider than the adults and are tightly packed with frass and boring dust except for the terminal portion of the gallery. Total gallery length is about 13 cm. Eggs are deposited in short rows along both sides of the egg gallery at the rate of between 4 and 14 eggs per centimetre of gallery.

Larvae bore outward from the egg gallery, and feed communally for the first two instars. The third and fourth instars feed in individual galleries. The larval stage is the predominant life stage during the first winter, although some parent adults and eggs may also be present. Two-year cycle spruce beetles pupate about 1 year after attack by the parent adults. Pupation generally lasts 10-15 days and takes place in cells at the end of the larval galleries.

The second winter is passed in the adult stage, either in pupal sites or at the base of infested trees. During the following summer, the brood adults emerge from their overwintering sites and attack new host material.

In Alaska, 2 years are required to complete a generation. In eastern North America and in the coastal areas of the Northwest, a 1-year cycle may be more common. Adults emerge and attack from June to August and the brood overwinters as larvae. They resume development the following spring and emerge as adults in June (Holsten et al., 1989).

Natural enemies

Top of page
Natural enemyTypeLife stagesSpecificityReferencesBiological control inBiological control on
Beauveria bassiana Pathogen
Coeloides dendroctoni Parasite Larvae
Dinotiscus dendroctoni Parasite Larvae
Enoclerus lecontei Predator Adults/Larvae/Pupae
Medetera aldrichii Predator Larvae
Rhopalicus tutele Parasite Canada Picea
Roptrocerus xylophagorum Parasite Larvae
Thanasimus undatulus Predator Adults/Larvae/Pupae

Notes on Natural Enemies

Top of page The natural enemy complex of the spruce beetle has been studied extensively and consists of a complex of parasitoids, invertebrate and vertebrate predators and nematodes. Three species of woodpeckers are known predators. The northern three-toed woodpecker (Picoides tridactylus) is the most effective because it feeds exclusively on the boles of trees. The effects of insect parasitoids and predators on spruce beetle populations can be quite variable. In some cases they can kill large numbers of spruce beetle life stages but have a minimal effect on the overall population (Schmid and Frye, 1977).

For further information on the natural enemies of D. rufipennis, see Bellows et al. (1998) and Schmid and Frye (1977).

Plant Trade

Top of page
Plant parts liable to carry the pest in trade/transportPest stagesBorne internallyBorne externallyVisibility of pest or symptoms
Stems (above ground)/Shoots/Trunks/Branches adults; eggs; larvae; nymphs; pupae Yes Pest or symptoms usually visible to the naked eye

Wood Packaging

Top of page
Wood Packaging liable to carry the pest in trade/transportTimber typeUsed as packing
Solid wood packing material with bark Spruce - crating, pallets, dunnage Yes

Impact

Top of page The spruce beetle is considered the most destructive insect pest of spruce forests in North America. This insect is normally present in small numbers in weakened or windthrown trees, large pieces of logging residues or fresh stumps. However, under favourable conditions, outbreaks can develop and kill extensive forests over large areas. Spruce beetle populations typically increase following severe storms that result in extensive windthrow. Large numbers of beetles emerging from the windthrow can attack standing trees. Other factors that can trigger outbreaks include large volumes of spruce logging debris, cutting of seismic lines for oil and gas exploration and road construction. When outbreaks develop in mature spruce forests, larger diameter trees are usually attacked first but spruces of all diameter classes can be killed. Stands that are slow growing are especially susceptible to prolonged outbreaks (Furniss and Carolin, 1977; Schmid and Frye, 1977; Holsten et al., 1989).

North American spruce forests have a long history of spruce beetle outbreaks. According to early records, spruce beetle was first recognized as a pest of spruce in the north-eastern USA in the early 1800s, when several outbreaks killed large numbers of trees (Hopkins, 1901). These outbreaks continued until the beginning of the twentieth century but have since dwindled to smaller outbreaks covering several thousand acres, presumably due to a reduction in the area of mature spruce forests (Weiss et al., 1985). This insect has also been a serious pest in the Rocky Mountains and in portions of Oregon and Washington (Furniss and Carolin, 1977). Historical records summarized by Schmid and Frye (1977) report on outbreaks in western Colorado in the mid 1870s. During this same period an outbreak killed more than 90% of the spruce on more than 5300 ha in southern New Mexico. Another massive outbreak occurred in western Colorado between 1942 and 1948 following a severe storm resulting in extensive windthrow. Spruce beetle has been a continuing problem in portions of Alaska since the early 1970s. This outbreak began to increase significantly in 1992 and peaked in 1996 when nearly 460,000 ha were infested (Ciesla and Coulston, 2002).

Environmental Impact

Top of page During outbreaks, widespread tree mortality alters the character of forests with a significant spruce component. Outbreaks modify stand structure by lowering tree diameter, height and stand density. In some cases spruce forests have been replaced by less desirable species, such as subalpine fir (Abies lasiocarpa) or paper birch (Betula papyrifera). Large outbreaks significantly reduce aboveground water loss by transpiration due to loss of spruce foliage. Extensive spruce mortality also increases water yield, resulting in increased amounts of water in rivers, lakes and streams. As the dominant spruce trees are killed, increased forage develops, which benefits some wildlife species. However, outbreaks adversely affect those species dependent on mature spruce forests for habitat (Holsten et al., 1989).

Threatened Species

Top of page
Threatened SpeciesConservation StatusWhere ThreatenedMechanismReferencesNotes
Rangifer tarandus (reindeer)No Details; Ecosystem change / habitat alterationUS Fish and Wildlife Service, 1994
Tamiasciurus hudsonicus grahamensis (Mount Graham red squirrel)USA ESA listing as endangered species USA ESA listing as endangered speciesArizonaEcosystem change / habitat alterationUS Fish and Wildlife Service, 2007

Detection and Inspection

Top of page Look for pitch tubes and/or boring dust on the bark surface and the presence of galleries and insect life stages in the cambium and inner bark on unprocessed logs or dunnage, crating or pallets containing bark strips.

Similarities to Other Species/Conditions

Top of page Dendroctonus rufipennis is distinguished from the closely related D. murrayanae with great difficulty. Morphological characteristics that separate the two species include a more coarsely granulated frons on D. rufipennis. The male genitalia of the two species are also different. Field characteristics that can be used to separate these two species include host differences (D. murrayanae infests Pinus contorta) and gallery structure (Wood, 1982).

In Alaska, Canada and the north-eastern USA, the Allegheny spruce beetle (Dendroctonus punctatus) also attacks spruce. This insect may be distinguished from spruce beetle by its uniformly brown colour (Holsten et al., 1989). D. rufipennis also resembles to some extent the Douglas-fir beetle (D. pseudotsugae). However, D. pseudotsugae is found on Pseudotsuga menziesii (Furniss and Carolin, 1977).

To ensure positive identification, bark beetles believed to be a new introduction, should be examined by a taxonomist with expertise in the family Scolytidae.

Prevention and Control

Top of page Cultural Control

A number of cultural tactics, designed to modify forest conditions, are available to manage spruce beetle infestations. Infested and susceptible spruce can be removed from the overstorey to encourage regeneration of a new, healthy, vigorous forest. Partial cuts can be used to remove infested and susceptible trees to improve the growth of the residual stand. Trap trees, green trees of large diameter (>46 cm), can be felled before adult flight to attract flying beetles. Trap trees must be removed from forests before the brood completes development and emerges (Holsten et al., 1989).

Biological Control

No biological control programme has been developed for spruce beetle. Unless large volumes of favourable host material exist, this insect is kept at low levels by a combination of factors including a complex of natural enemies (Bellows et al., 1998).

Chemical Control

Several tactics involving chemicals have been used. The application of chemicals to the boles of infested trees to kill broods and emerging adults has been used. However, as is the case with other bark beetles, this procedure is expensive and of marginal effectiveness as long as forest conditions are favourable for the development of spruce beetle outbreaks. The boles of high value, uninfested trees in recreation sites or homesites can be sprayed with a residual insecticide to prevent attack. This treatment can protect trees for up to 2 years (Holsten et al., 1989).

Pheromonal Control

Aggregating pheromones can increase the effectiveness of trap trees. The anti-attractant pheromone methylcyclohexenone shows promise as a repellent but is not yet an operational pest management tactic (Holsten et al., 1989).

Mechanical Methods

Infested logging debris or windthrow can be exposed to direct sunlight to kill spruce beetle broods. Infested material is cut into 1.5-2 m lengths and rotated at 2-week intervals to expose the bark surface to the sun. This technique is effective in the Rocky Mountains but not in Alaska (Holsten et al., 1989).

Infested material can be piled and burned to destroy broods. Only the bark has to be burned (Holsten et al., 1989).

Field Monitoring

Monitoring of spruce beetle consists of aerial and ground surveys designed to locate groups of dead and dying trees and confirm the presence of infestations. In areas where this insect has a history of causing damage, these surveys are conducted on an annual basis. Attractant pheromones can also be used to monitor the relative abundance of adult beetles.

Integrated Pest Management

Integrated pest management of spruce beetle consists of monitoring of forests for the presence of infestations and management to keep forests in a healthy growing condition. Guidelines are available to rate the hazard of spruce forests for susceptibility to spruce beetle attack (Alexander, 1986). The removal of infested and high-risk trees, treatment of logging debris and windthrow, and the judicious use of trap trees are effective pest management tactics. Attacks in high value trees can be prevented by the application of insecticides. Many forests with a heavy spruce component and susceptible to outbreaks of spruce beetle occur at high altitudes (e.g. the Rocky Mountains) or remote, inaccessible areas (e.g. Alaska) where it is logistically difficult to implement pest management programmes. Therefore, this insect remains a major threat to North American spruce forests.

References

Top of page

Alexander RR, 1986. Silvicultural systems and cutting methods for old-growth spruce-fir forests in the central and southern Rocky Mountains. USDA Forest Service, Rocky Mountain Forest and Range Experiment Station, General Technical Report RM-GTR-126.

Bellows TS, Meisenbacher C, Reardon RC, 1998. Biological control of arthropod forest pests of the Western United States: a review and recommendations, 121 pp.

CABI/EPPO, 1998. Distribution maps of quarantine pests for Europe (edited by Smith IM, Charles LMF). Wallingford, UK: CAB International, xviii + 768 pp.

CABI/EPPO, 2004. Dendroctonus rufipennis. Distribution Maps of Plant Pests, No. 661. Wallingford, UK: CAB International.

Cibrián Tovar D, Méndez Montiel JT, Campos Bolaños R, Yates III HO, Flores Lara JE, 1995. Forest Insects of Mexico. Chapingo, México: Universidad Autonoma Chapingo. Subsecretaria Forestal y de Fauna Silvestre de la Secretaria de Agricultura y Recursos Hidraulicos, México. United States Department of Agriculture, Forest Service, USA. Natural Resources Canada, Canada. North American Forestry Commission, FAO, Publication 6.

Ciesla WM, Coulston J, 2002. Report of the United States on the criteria and indicators for sustainable management of temperate and boreal forests of the United States, Criterion 3 - Maintenance of ecosystem health and vitality, Indicator 15, Area and percent of forest affected by processes or agents beyond the range of historic variation. USDA Forest Service, On line: http://www.fs.fed.us/research/sustain/.

EPPO, 2014. PQR database. Paris, France: European and Mediterranean Plant Protection Organization. http://www.eppo.int/DATABASES/pqr/pqr.htm

Furniss RL, Carolin VM, 1977. Western Forest Insects. Washington DC, USA: US Department of Agriculture Forest Service, Miscellaneous Publication No. 1339.

Holsten EH, Thier RW, Schmid JM, 1989. The spruce beetle. USDA Forest Service, Forest Insect and Disease Leaflet 127.

Hopkins AD, 1901. Insect enemies of the spruce in the Northeast. USDA Bureau of Entomology, Washington D.C., Bulletin 28, 80 pp.

Schmid JM, Frye RH, 1977. Spruce beetle in the Rockies. USDA Forest Service, Rocky Mountain Forest and Range Experiment Station, Fort Collins, Colorado, USA. General Technical Report RM-49.

Sun J, Gillette NE, Miao Z, Kang L, Zhang Z, Owen DR, Stein JD, 2003. Verbenone interrupts attraction to host volatiles and reduces attack on Pinus tabuliformis (Pinaceae) by Dendroctonus valens (Coleoptera: Scolytidae) in the People's Republic of China. Canadian Entomologist, 135(5):721-732.

US Fish and Wildlife Service, 1994. In: Recovery Plan for Woodland Caribou in the Selkirk Mountains. US Fish and Wildlife Service, 71 pp.

US Fish and Wildlife Service, 2007. In: Mount Graham Red Squirrel (Tamiasciurus hudsonicus grahamensis). 5-Year Review: Summary and Evaluation. US Fish and Wildlife Service, 24 pp.

Weiss MJ, McCreery LR, Millers I, Miller-Weeks M, O'Brien JT, 1985. Cooperative survey of red spruce and balsam fir decline and mortality in New York, Vermont and New Hampshire, 1984. USDA Forest Service, Northeastern Area, Broomall, PA, USA, Report NA-TP-11.

Wood SL, 1963. A revision of the bark beetle genus Dendroctonus Erichson (Coleoptera: Scolytidae). The Great Basin Naturalist, 23:1-117.

Wood SL, 1982. The bark and ambrosia beetles of North and Central America (Coleoptera: Scolytidae), a taxonomic monograph. Great Basin Naturalist Memoirs, No. 6:1359 pp.

Distribution Maps

Top of page
You can pan and zoom the map
Save map