Ips sexdentatus

Name:   Ips sexdentatus
Pest Authorities:  (Boerner)
Taxonomic Position:  Insecta: Coleoptera: Scolytidae
Sub-specific Taxon:  
Pest Type:   Insect
Common Name(s):
   12-zähniger Kiefernborkenkäfer (German)
   Le stenographe (French)
   Perforadora de pino (Spanish)
   Six-spined engraver beetle (English)
   Tolvtannent barkbille (Norwegian)
   Bostrichus pinastri Bechstein
   Bostrichus stenographus Duftschmidt
   Dermestes sexdentatus Boerner
   Ips typographus De Geer
Numerical Score:  6
Relative Risk Rating:  High Risk
Uncertainty:   Very Uncertain
Uncertainty in this assessment results from: Uncertainty in this assessment results from lack of information on the ability of Ips sexdentatus to compete with the complex of Ips engraver beetles (25 species) indigenous to North America and become established.

Establishment Potential Is High Risk
The relevant criteria chosen for this organism are:  
  • Suitable climatic conditions and suitable host material coincide with ports of entry or major destinations.
  • Organism has demonstrated ability to utilize new hosts
  • Organism has active, directed host searching capability or is vectored by an organism with directed, host searching capability.
  • Organism has high inoculum potential or high likelihood of reproducing after entry.
Justification: Suitable climatic conditions exist for survival and establishment of Ips sexdentatus at most North American ports of entry. I. sexdentatus responds to both host and insect produced attractants giving it a directed host searching capability and a good likelihood of reproducing after introduction. I. sexdentatus could easily be introduced into North America via unprocessed conifer logs, or wooden crating, pallets or dunnage containing bark strips. Successful establishment of this insect is dependent on its ability to compete effectively with the large complex of Ips bark beetles indigenous to North America (25 species) including the North American six-spined engraver beetle, Ips calligraphus, which is its North American ecological equivalent.

Spread Potential Is High Risk
The relevant criteria chosen for this organism are:  
  • Organism has demonstrated the ability for redistribution through human-assisted transport.
  • Organism has a high reproductive potential
  • Potential hosts have contiguous distribution.
  • Newly established populations may go undetected for many years due to cryptic nature, concealed activity, slow development of damage symptoms, or misdiagnosis.
  • Organism has broad host range.
Justification: Ips sexdentatus adults are strong fliers capable of covering several km in search of suitable host material. They are also subject to wind dispersal. This insect could be easily introduced into North America via unprocessed conifer logs, or wooden crating, pallets and dunnage containing bark strips. This bark beetle was intercepted at US ports of entry on 157 occasions between 1985 and 2000 (Haack 2001). Newly established populations could go undetected for long periods because of its cryptic nature and similarity in appearance and habits of indigenous species ofIps. To most entomologists, Ips sexdentatus would appear to be similar in appearance to the North American six-spined engraver beetle, Ips calligraphus. Therefore, if this insect were to become established in North America, it is expected to behave in a manner similar to its indigenous counterpart. This would make eradication techniques difficult, if not impossible, to implement. I. sexdentatus is capable of attacking a large number of hosts and could adapt to North American pines.

Economic Potential Is Moderate Risk
The relevant criteria chosen for this organism are:  
  • Organism attacks hosts or products with significant commercial value (such as for timber, pulp, or wood products.
  • Damage by organism causes a decrease in value of the host affected, for instance, by lowering its market price, increasing cost of production, maintenance, or mitigation, or reducing value of property where it is located.
  • Organism may cause loss of markets (domestic or foreign) due to presence and quarantine significant status.
Justification: Assuming that this insect will behave in North America as it does in Eurasia, I. sexdentatus will confine its attacks to weakened, dying or dead trees. This insect would become one of the complex of Ips engraver beetles present in North America and would add little to the economic impact already caused by indigenous species.

Ips attacks introduce blue stain fungi, Ophiostoma spp., into host trees, which can result in loss of value.

Environmental Potential Is Moderate Risk
The relevant criteria chosen for this organism are:  
  • Introduction of the organism would likely result in control/eradication programs that may have potential adverse environmental affects.
Justification: Provided that Ips sexdentatus behaves in North America as it does in its natural range, little or no adverse environmental impact is expected. This insect would become one of a large complex of insect involved in the decomposition of dead wood.

Pines, Pinus spp. are the predominant hosts of this insect across its natural range. In Europe and the Near East, Scotch pine, Pinus sylvestris, Austrian pine, Pinus nigra, maritime pine, Pinus pinaster, Calabrian pine, Pinus brutia and Pinus heldrichii (=Pinus leucodermis) are reported hosts (Grüne 1979, Selmi n.d.). In Thailand, Pinus merkusii and Pinus caribaea (exotic) are hosts (Vongkalung 1990).

Other conifer hosts in Europe and Asia include: Abies alba, Abies normanndiana (=A. bormuelleriana), Larix decidua, Larix sibirica, Picea abies, Picea orientalis (Grüne 1979, Selmi n.d.) and Douglas-fir, Pseudotsuga menzeisii.

      Ips sexdentatus occurs from Turkey across Russia to China and south to Thailand (Selmi n.d., Vongkalung 1990). This insect is widely distributed in China and is reported from Gansu, Helongjiang, Henan, Jilin, Liaoning, Inner Mongolia, Shaanxi, Sichuan, Huanan and Yunnan Provinces (Zhu Chang-qing et al 1999, Zhang Zhizhong et al. 1997). It also occurs in Japan, Korea, Thailand, Turkey and Asian Russia (Wood and Bright 1992).
     This insect is widely distributed across Europe from the British Isles, Spain and France east to Turkey and European Russia (Browne 1968). Countires from which it is reported include Austria, Belgium, Bulgaria, Czech Republic, Denmark, England, Estonia, Finland, France (including Corsica), Germany, Greece, Hungary, Italy (including Sardinia), Latvia, Luxembourg, Netherlands, Norway, Poland, Portugal, Romania, Spain, Sweden, Switzerland, European Russia (Bright and Skidmore 2002, Wood and Bright 1992)
The genus Ips is a large genus of bark beetles (about 60 species) indigenous to conifer forests in Asia, Europe and North America. Twenty-five species are known from North American pines and spruces and several are regarded as important pests (Drooz 1985, Furniss and Carolin 1977, Cibrion Tovar et al. 1995, Wood 1982).

Ips sexdentatus prefers to attack large trees with thick bark. This insect typically has two generations per year with adult flight periods from April to May and July to August. In Mediterranean regions of Europe, I. sexdentatus can undergo a third generation (Abgrall and Soutrenon 1991). Attacks are initiated by the males, who construct nuptial chambers under the bark and are subsequently joined by 2-5 females. After mating, each female constructs a longitudinal egg gallery and deposits eggs in individual niches along each side of the gallery. The young larvae feed in galleries perpendicular to the egg galleries. Larval galleries increase as the larvae increase in body size. Pupation takes place in round chambers constructed at the ends of the larval galleries. Adults require maturation feeding before reaching sexual maturity (Abgrall and Soutrenon 1991, Grüne 1979).

Economic Impact:    Ips sexdentatus can kill trees of commercial importance. Ips attacks also introduce blue stain fungi, Ophiostoma spp., into host trees, which hasten the death of trees, discolor the wood and can result in loss of lumber grade and value.

Environmental Impact:   Because this insect confines its attacks to weakened, windthrown or recently cut trees, it has little or no adverse environmental impact. Ips sexdentatus usually confines its attacks to trees that have been weakened by site or climatic factors, other insects, fungi etc., recently cut trees or windthrow. This insect rarely attacks healthy vigorous trees and is generally considered to be a secondary insect throughout its native range. This bark beetle is often part of an insect complex that includes Ips erosus, Tomicus piniperda, T. minor, and twig beetles of the genus Pityogenes (Abgrall and Soutrenon 1991) that contribute to the decomposition of dead conifer wood.

Control:    Parasitoids, predators, and fungi are natural control agents of Ips sexdentatus. In a recent study in the Black Sea region of Turkey, two species of parasitoids and 26 predaceous insects were found associated with Ips sexdentatus (Yüksel 1997).

Silvicultural tactics, including the removal of severely weakened trees, is recommended to prevent buildup of infestations. Rapid salvage and processing or spraying of infested trees containing bark beetle brood with a contact insecticide is also used to reduce losses (Abgrall and Soutrenon 1991).

In Europe, where harvested logs are often left in the forest for extended periods, bark beetle breeding attacks are prevented by debarking the logs (Author’s observation).

Symptoms:    The first indication of attack by Ips sexdentatus is that infested trees fade from green to yellow to reddish brown.

Breeding attacks are characterized by the presence of reddish-brown boring dust on the bark surface of trees, freshly cut logs or windthrow. If relatively vigorous trees are attacked, pitch tubes are found in bark crevasses. The gallery pattern in the cambial region of infested trees consists of a nuptial chamber and two to five longitudinal egg galleries ca 15 to 35 cm long. Breeding attacks are accompanied by blue stain in the woody tissue (Abgrall and Soutrenon 1991).

Round exit holes, ca 4 mm in diameter, can be seen on the bark surface of trees where this insect has completed its life cycle and adults have emerged.

Morphology:    Ips sexdentatus is a large bark beetle, averaging 5.5-8.2 mm in length and dark brown in color. The adults are typical bark beetles of the subfamily Ipinae of the family Scolytidae. The head is covered by a thoracic shield and is not visible when viewed dorsally and the declivity is concave with each side is armed with a series of six conspicuous spines (Abgrall and Soutrenon 1991, Grüne 1979).

Eggs are pearly white. The larvae are white, c-shaped grubs with an amber colored head capsule. Mature larvae are from 5 to 8 mm long. The pupae are white, mummy-like and have some adult features including wings that are folded behind the abdomen.

Testing Methods for Identification:    Species identification of bark beetles (Family Scolytidae) must be done from the adult stage. Identification of insects suspected of being exotic species of Ips should be examined by a qualified insect taxonomist with expertise in the family Scolytidae.

Adult beetles are capable of flying up to 4 km (ca. 2.4 miles) in search of suitable host material (Byers 1995). In addition, adults are subject to dispersdal by wind.

Transport of unprocessed logs, wood products or wooden packing material, dunnage or pallets containing bark strips can provide a means of introduction of immature stages (larvae and pupae) and adults. During the period 1985-2000, Ips sexdentatus was intercepted at US ports of entry 157 times, mostly from wooden crating (Haack 2001).

Abgrall, J.F.; Soutrenon, A. 1991. La forêt et ses ennemis. Paris, France: Centre National du Machinisme Agricole du Genie Rural des Eaux et des Forets (CEMAGREF) (In French).
Bright, D.E.; Skidmore, R.E. 2002. A catalog of Scolytidae and Platypodidiae (Coleoptera), Supplement 2 (1995-1999). Ottawa: National Research Council (NRC) Press, 523 pp.
Browne, F.G. 1968. Pests and diseases of forest plantation trees - An annotated list of the principal species occurring in the British Commonwealth. Oxford, UK: Clarendon Press, 1330 pp.
Byers, J.A. 1995. Host tree chemistry affecting colonization in bark beetles. In: Carde, R.T; Bell, W.J., (editors). Chemical Ecology of Insects. New York: Chapman and Hall.
Cibrion Tovar, D.; Méndez Monteil , J.T.; Campos Bolaòos; Yates, H.O. III, Flores Lara, J. 1995. Forest insects of Mexico. North American Forestry Commission, FAO, Publication 6, 453 pp.
Drooz, A.T. 1985. Insects of eastern forests. USDA Forest Service, Miscellaneous Publication 1426, 608 pp.
Furniss, R.L.; Carolin, V.M. 1977. Western forest insects. USDA Forest Service, Miscellaneous Publication 273, 654 pp.
Grüne, S. 1979. Handbuch zur bestimmung der europaischen Borkenkäfer (Brief illustrated key to European bark beetles). Hannover, Germany: Verlag M.& H. Schaper, 182 pp. (In German and English).
Haack, R.A. 2001. Intercepted Scolytidae (Coleoptera) at United States ports of entry: 1985-2000. Integrated Pest Management Reviews 6(3): 253-282.
Selmi, E. n.d.. Scolytidae of Turkey. On line: Http://www.orman.istanbul.edu.tr/ento/.
Stephen, F.M.; Gregoire, J.C. 2001. Introduction and establishment of exotic bark beetles. Exotic Forest Pests Online Symposium, On line: http://exoticpests.aspnet.org/papers/stephen.htm.
Vongkalung, C. 1990. Chemical protection of freshly-felled pine and eucalypt logs in Thailand. In: Proceedings of the IUFRO Workshop on Pests and Diseases of Forest Plantations in the Asia-Pacific Region. FAO, Regional Office for Asia and the Pacific (RAPA), Bangkok, Thailand, RAPA Publication 1990/9, pp. 272-277.
Wood, S.L. 1982. The bark and ambrosia beetles of North and Central America (Coleoptera: Scolytidae), a taxonomic monograph. Great Basin Naturalist Memoirs 6, 1359 pp.
Wood, S.L.; Bright, D.E. 1992. A catalog of Scolytidae and Platypodidae (Coleoptera), Part 2: Taxonomic index. Great Basin Naturalist Memoirs 13, 1553 pp.
Yuksel, B. 1997. Predator and parasite relations affecting infestations of Ips sexdentatus in forests of the eastern Black Sea Region. Proceedings XI World Forestry Congress, Antalya, Turkey, 13-22 October 1997, Summaries of Voluntary Papers, Volume 1, Topic 5.
Zhang Zhizhong, et al. 1997. Forest entomology. Chinese Forest Press, 491 pp. (In Chinese).
Zhu Chang-qing, et al. 1999. Insect fauna of Henan - Coleoptera. Henan Scientific and Technological Publishing House, 413 pp. (In Chinese).
William M. Ciesla
Name and Address of the First Author:
William M. Ciesla
Forest Health Management International
2248 Shawnee Court
Fort Collins, CO
USA 80525
CREATION DATE:        08/18/01

Selected images from Forestry Images (www.forestryimages.org)
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Photo by Yves Bancillon,
Office National des Forêts - France


closeup showing head regulated U.S. exotic
Photo by Steve Passoa,


Photo by Gyorgy Csoka,
Hungary Forest Research Institute


Photo by Gyorgy Csoka,
Hungary Forest Research Institute


Photo by Gyorgy Csoka,
Hungary Forest Research Institute


larval sawdust deposition down of an attacked pine
Photo by Fabio Stergulc,
University of Udin