Dendroctonus rufipennis

Kirby, 1837

spruce beetle, great spruce bark beetle

Dendroctonus rufipennis, the spruce , is a bark beetle native to North America and a major pest of spruce forests. measure 4–7 mm in length and are among the larger bark beetles in spruce. The undergoes a facultative of 1, 2, or 3 years, with 2-year cycles being most common. have caused extensive tree mortality across western North America, particularly affecting Engelmann and white spruce. Climate warming and drought stress are key factors driving increases.

Dendroctonus rufipennis by (c) Matt Bowser, some rights reserved (CC BY), uploaded by Matt Bowser. Used under a CC-BY license.1919. Entomological Ranger W.E. Glendinning checking felled spruce infested with spruce beetle. Oregon Coast Range. (32870445253) by R6, State & Private Forestry, Forest Health Protection. Used under a Public domain license.Spruce bark beetle kill burned area after fire by U.S. Fish and Wildlife Service. Used under a Public domain license.

Pronunciation

How to pronounce Dendroctonus rufipennis: //dɛnˈdrɑktənəs ruːfɪˈpɛnɪs//

These audio files are automatically generated. While they are not always 100% accurate, they are a good starting point.

Identification

are 4–7 mm long, relatively large for a bark beetle. Attack signs include red boring dust in bark crevices and pitch tubes, particularly on weakened or recently dead trees. Galleries in the inner bark run parallel to the wood grain, approximately 12.5 cm long, with about 6 galleries per 929 cm². Larval galleries contain 3–4 groups with roughly 100 eggs per gallery.

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Habitat

Mature and overmature spruce forests; prefers large-diameter, slow-growing trees with reduced radial growth. Strongly attracted to blowdowns, cull logs, and freshly cut logs.

Distribution

Transcontinental North America: Canada (British Columbia, Alberta, Saskatchewan, Manitoba, Ontario, Quebec, Newfoundland and Labrador, Nova Scotia, Yukon, Northwest Territories, Nunavut, New Brunswick); USA (Alaska, Colorado, Wyoming, Montana, Maine, Arizona, Idaho, Utah, Michigan, Minnesota, Nevada, New Hampshire, New Mexico, New York, Oregon, Pennsylvania, South Dakota, Vermont, Washington, Wisconsin, California).

Seasonality

and attack period begins in June or soon after snowmelt around trees. construct tunnels for first in June, second tunnels in late July. Some brood 1 adults emerge in late July; others overwinter as mature larvae and emerge the following July.

Diet

Phloem of spruce trees (Picea spp.).

Host Associations

  • Picea glauca - primary white spruce
  • Picea engelmannii - primary Engelmann spruce
  • Picea sitchensis - Sitka spruce
  • Picea pungens - Colorado blue spruce

Life Cycle

Facultative 1-, 2-, or 3-year ; 2-year most common. One-year cycle occurs at lower elevations, warmer sites, or during abnormally warm years. Three-year cycle occurs at high elevations, cold sites, or during unseasonably cold years. hatch in 3–4 weeks. Larvae vary in size by onset of dormancy; development resumes following June, occurs during summer, in late summer or early fall. Adults emerge, fall or crawl to ground, and re-enter same tree to hibernate, often clumping under bark. Prepupal is facultative and temperature-dependent; daily below approximately 9°C above the developmental threshold (6.1°C) induce diapause, while 10°C or more above threshold averts diapause. Diapause induction occurs no later than third larval instar.

Behavior

Mass attacks on trees mediated by . construct galleries parallel to wood grain in inner bark. Parent females may produce sister : re-emerging to deposit additional eggs in new hosts later in the season. adults often clump together under bark. Adults re-emerge from hibernation in spring to fly to green trees, blowdowns, cull logs, or stumps.

Ecological Role

Primary disturbance agent in spruce forest ; accelerates by killing mature and overmature spruce. blue-stain fungus Leptographium abietinum, which may aggravate tree damage. Associated yeasts (particularly Wickerhamomyces canadensis) may affect fungal and growth through volatile emissions.

Human Relevance

Major pest of commercial forestry; responsible for billions of board feet of timber loss. in Alaska (1992–1999) destroyed 2.3 million acres; Utah (1990s) 122,000 acres; British Columbia losses of 3 billion board feet. Climate warming has increased outbreak frequency and severity. Management strategies include maintaining tree radial growth rates and removing blowdowns and cull material.

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