GREATER EUROPEAN SPRUCE BEETLE
Dendroctonus micans (Kugelann)-- Scolytidae
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This bark beetle, probably native to coniferous forests of eastern Siberia, is one of only two Dendroctonus species occurring in the palearctic region. Dendroctonus micans is primarily a pest of spruce, Picea spp., but will occasionally attack Pinus sylvestris L. The beetle has been expanding its range for many years and is still spreading. About 200,000 ha are currently suffering from epizootics and recently invaded areas include Great Britain, France, The Georgian S.S.R. and Turkey (Grégoire et al. 1987, Evans 1985). In the inner parts of its range where the beetle has been established for a long time populations remain at low densities and it is not a pest.
This bark beetle differs from the more aggressive North American Dendroctonus species in that it attacks its host tree in low numbers, killing the bark in patches. Successive attacks over a period of five to eight years may be necessary to kill a tree except during beetle outbreaks (Grégoire 1985). The beetle shows kin-mating, gregarious larvae and apparently lacks associated pathogenic fungi that are characteristic of many Scolytidae. Dendroctonus micans has very few natural enemies which may be due to its unique biology that seems to protect the beetles from competitors and generalist natural enemies by the defenses of its living host (Everaerts et al. 1988).
One specific predator Rhizophagus grandis Gyllenhal is very abundant in areas where the bark beetle has been present for long periods of time. This rhizophagid beetle is believed to be responsible for maintaining the low, stable D. micans population in these areas (Kobakhidzi 1965, Grégoire 1976, Moeck & Safranyik 1984).
A massive biological control project was initiated against D. micans in Georgia S.S.R. in 1963 (Kobakhidze 1965). The spruce beetle had extended its range into Georgia following World War II in timber imported from the north. A predator relocation program was planned as the predator did not follow its host. Rhizophagus grandis was released in large numbers as larvae and adults on spruce trees infested by D. micans (Kokakhidze et al. 1968). Effective control apparently has been achieved (Grégoire et al. 1987, Dahlsten & Mills 1999).
First observed in the Massif Central of France in the early 1970's, D. micans was targeted for biological control in a program funded by the European Economic Community in 1983. Its main thrust was to establish the predator, R. grandis (Grégoire et al. 1987). A similar program was initiated in 1983 in Great Britain (Evans 1985, Evans & King 1987). Evaluations are still in progress, but knowledge that the predator is attracted to the frass of three North American Dendroctonus species (Miller et al. 1987) suggests its possible use against species other than D. micans (Dahlsten & Mills 1999).
REFERENCES: [Additional references may be found at: MELVYL Library ]
Dahlsten, D. L. & N. J. Mills. 1999. Biological Control of Forest Insects. In: Bellows, T. S. & T. W. Fisher (eds.), Handbook of Biological Control: Principles and Applications. Academic Press, San Diego, New York. 1046 p.
Evans, H. F. 1985. Great spruce bark beetle, Dendroctonus micans: an exotic pest new to Britain. Antenna 9: 117-21.
Everaerts, C., J.-C. Grégoire & J. Merlin. 1988. The toxicity of spruce monoterpenes to bark beetles and their associates. In: W. J. Mattson et al. (eds.), Mechanisms of Woody Plant Resistance to Insects and Pathogens. Springer-Verlag, New York. 416 p.
Grégoire, J.-C. 1976. Note sur deux ennemis naturels de Dendroctonus micans Kug. en Belgique. Bull. Ann. Soc. r. belge Entomol. 112: 208-12.
Grégoire, J.-C., M. Balsier, J. Merlin & Y. Naccache. 1987. Interactions between Rhizophagus grandis (Coleoptera: Rhizophagidae) and Dendroctonus micans (Coleoptera: Scolytidae) in the field and laboratory. Their application for the biological control of D. micans in France. Proc. Symposium on Potential for Biological Control of Dendroctonus and Ips Bark Beetles. Ann. Meeting Ent. Soc. Amer., 9 Dec. 1986. Reno, Nevada (in press).
Kobakhidze, D. N. 1965. Some results and prospects of the utilization of beneficial entomophagous insects in the control of insect pests in Georgian SSR (USSR). Entomophaga 10: 323-30.
Moeck, H. & L. Safranyik. 1984. Assessment of predator and parasitoid control of bark beetles. Canadian Forestry Service, Pacific Forest Research Center. Information Report BC-X-248. 24 p.