Spruce Beetle Biological Control

Dendroctonus rufipennis Kirby

From: Bellows, Thomas S. ,Carol Meisenbacher, and Richard C. Reardon, 1998, Biological Control of Arthropod Forest Pests of the Western United States: A Review and Recommendations, USDA, FS, FHTET-96-21.

Origin: North America.

Range in North America: Throughout the range of Picea spp. (spruces).

Plant hosts and damage: In the West, primarily Picea engelmannii, Picea glauca, and Picea sitchensis. Adults bore into bark, create egg galleries between the bark and the wood, and oviposit. Larvae feed between the bark and the wood. Heavy infestations kill the host tree.

Natural Enemies: Vertebrate predators are known to include woodpeckers. The parasitic nematodes Sphaerularia dendroctoni Massey and Contortylenchus reversus Thorne infect adult beetles, but the impact of such infection on the beetles is unknown. In one study such nematode infection did not reduce adult fertility (McCambridge and Knight 1972). Fewer studies of the natural enemies of D. rufipennis have been reported than for other members of the genus (Table 7). A few studies have reported a number of predaceous or parasitic invertebrates associated with wood infested with D. rufipennis. These records may be viewed as tentative or possible natural enemies of this species. These association records include Dinotiscus dendroctoni (Ashmead), Dinotiscus eupterus (Walker), Medetera signaticornis Loew., Roptrocerus xylophagorum (Ratzeburg) and Rhyzophagus spp. (Gara et al. 1995), and Rhyzophagus dimidiatus (Massey and Wygant 1954). Thanasimus dubius Fab. is attracted to the D. refupennis aggregation pheromone (Lindgren 1992), indicating a possible predatory relationship.

Table 7. Natural enemies of Dendroctonus rufipennis

¹McCambridge and Knight 1972
²Gara et al. 1995

Pest Status:The beetle is normally present in small numbers in weakened or windthrown trees (Furniss and Carolin 1977). Outbreaks can occur, and cause extensive damage. In Colorado from 1942 to 1948, 3.8 billion board feet of spruce were killed by this beetle (Wygant and Nelson 1949). The life cycle varies, requiring a single year in coastal populations, 2 years in the main distribution of P. engelmannii, and 3 years at high elevations. Harvesting stands of overmature spruce is effective in preventing the development of outbreaks. Other silvicultural measures are discussed by Furniss and Carolin (1977).

Biological Control: No biological control program has been mounted against this species. Spruce beetle populations are normally kept at low levels by a combination of factors, which include predation by woodpeckers, insect predators and parasitoids, and possibly parasitic nematodes.

Recommendations: The start of an outbreak is difficult to detect in this species. Direct control can be costly, and management should be focused on prevention of outbreaks. Such management should include sanitation, timely harvesting, and monitoring for infestations. Natural enemies are little known for this species. Additional research into the impact of natural enemies and their ability to respond to population increases of their hosts may prove beneficial in defining practices that would more effectively utilize natural control.

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