Eastern larch beetle
Dendroctonus simplex (LeConte) (Coleoptera: Curculionidae, Scolytinae)
Orientation to pest
Eastern larch beetle, Dendroctonus simplex (LeConte), is a native North American bark beetle whose only important host is eastern larch, Larix larcina (Du Roi ) K. Koch. The species overwinters as larvae or adults in galleries. Eggs are laid in groups along an egg gallery made by the female in the inner bark and outer sapwood. Larval tunnels are short and occur in the inner bark. There are up to three generations per year. Before the 1970s, this bark beetle was only known to attack dying or recently felled trees. Since then, however, a series of large outbreaks in healthy stands have occurred in both Canada and the United States. Some of these bark beetle outbreaks followed outbreaks of the defoliating larch sawfly Pristiphora erichsonii (Hartig), which had produced many stressed or dying larch trees. While the exact causes of these population fluctuations are unknown, some authors have attributed outbreaks to the maturing of larch stands over large areas, which lowers host resistance.
Hosts commonly attacked
Hosts of this species are eastern larch (L. larcina), and occasionally red spruce (Picea rubens Sargent).
Distribution
This bark beetle is found in the USA from New England south to West Virginia, and west to Minnesota. It is also found in Alaska and in Canada from the Atlantic to the Pacific coast.
Images of eastern larch beetle
| Figure 1. Adults of eastern larch beetle, Dendroctonus simplex, in galleries | Figure 2. Eggs of eastern larch beetle | Figure 3. Larva of eastern larch beetle |
| Figure 4. Pupa of eastern larch beetle | Figure 5. Larval galleries at surface of wood made by eastern larch |
Important biological control agents related to this pest species
Eastern larch beetle has a large complex of natural enemies that have been studied in a number of locations (see Van Driesche et al. 1996 for a review). Some of the natural enemies reported include the dolichopodid fly Medetera gaspensis Bickel and the rhizophagid beetle Rhizophagus dimidiatus Mannerheim (both predators) and the parasitoids Spathius canadensis Ashmead (Braconidae) and Rhopalicus tutela (Walker) and Roptrocerus xylophagorum (Ratzeburg).
Web links for information on eastern larch beetle
Articles
- Duncan, B. 1987. An illustrated guide to the identification and distribution of the species of Dendroctonus Erichson (Coleoptera: Scolytidae) in British Columbia. Journal of the Entomological Society of British Columbia 84: 101-112.
- Langor, D. W. and A. G. Raske. 1988. Annotated bibliography of the eastern larch beetle, Dendroctonus simplex LeConte (Coleoptera: Scolytidae).Information Report - Newfoundland Forestry Centre, Forestry Canada (N-X-266), 1988, 38 pp.
- Langor, D. W. and A. G. Raske. 1988. Mortality factors and life tables of the eastern larch beetle, Dendroctonus simplex (Coleoptera: Scolytidae), in Newfoundland. Environmental Entomology 17: 959-963.
- Langor, D. W. and A. G. A. Raske. 1989. A history of the eastern larch beetle, Dendroctonus simplex (Coleoptera: Scolytidae), in North America. Great Lakes Entomologist 22: 139-154.
- Van Driesche, R. G., S. Healy, and R. C. Reardon. 1996. Biological control of arthropod pests of the northeastern and north central forests in the United States: a review and recommendations. USDA FS, FHTET-96-19, Morgantown, West Virginia, pp. 58-59 http://www.forestpestbiocontrol.info/fact_sheets/documents/arthropodpestsnortheastern_northcentral.pdf
