''Dendroctonus pseudotsugae'', the Douglas-fir beetle, is a species of
bark beetle
A bark beetle is the common name for the subfamily of beetles Scolytinae. Previously, this was considered a distinct family (Scolytidae), but is now understood to be a specialized clade of the "true weevil" family (Curculionidae). Although the ...
found in western North America. Three subspecies exist that correspond to the subspecies of
Douglas-fir
The Douglas fir (''Pseudotsuga menziesii'') is an evergreen conifer species in the pine family, Pinaceae. It is native to western North America and is also known as Douglas-fir, Douglas spruce, Oregon pine, and Columbian pine. There are three va ...
. The beetles also infest downed
Larch
Larches are deciduous conifers in the genus ''Larix'', of the family Pinaceae (subfamily Laricoideae). Growing from tall, they are native to much of the cooler temperate northern hemisphere, on lowlands in the north and high on mountains furt ...
trees.
Outbreaks often occur in conjunction with drought, root rot diseases, overcrowding, damage by insects that damage foliage, and environmental disturbance. This insect is part of the western forest ecosystem, playing a role in thinning weak trees in a stand.
Adult Douglas-fir beetles are light brown when young and become dark brown or black with reddish wing covers. They are somewhat hairy and range in size from 4.4 to 7 mm. The larvae are small, legless, the size of grains of rice, and white. Pupae are white to cream colored. Visible evidence of infestation includes patches of orange to reddish-brown boring dust in the bark or at the base of the tree. Resin streamers from attacks higher in the tree may also be present. Inside the bark, 6 to 30 inch egg galleries run parallel with the grain. Eggs are laid on either side of the gallery and when they hatch, the larvae mine perpendicular to the galleries.
References
External links
* http://www.fs.usda.gov/Internet/FSE_DOCUMENTS/stelprdb5187396.pdf
* http://www.barkbeetles.org/douglasfir/dfb.html
Beetles of North America
Scolytinae
Insect pests of temperate forests
Woodboring beetles
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