Taxonomic name: Ips typographus (DeGreer, 1775)
Synonyms: Bostrichus octodentalis Paykull , Dermestes typographus Linneaus, Ips japonicus Niijima
Common names: Buchdrucker (German), eight-toothed spruce bark beetle, European spruce bark beetle (English), Gran scolyte de l'epicea (French), Grandbarkbillen (Norwegian), Großer 8 - zähniger Fichtenborkenkäfer, Le typographe de l'epicea
Organism type: insect
Ips typographus the European spruce bark beetle has caused many problems in Europe and Asia. It is a pest that mostly infects damaged spruce trees, but can also damage healthy trees as well. The effects of this pest have caused a great deal of economic loss as well as ecosystem change. Populations have increased throughout Asia and Europe, and a possibility of further expansion can exist as a cause of increasing temperature change. The importance of managing this pest has been realized, and speculation exists for possible methods of controlling and preventing damage caused by this species.
natural forests, planted forests
Outbreaks of Ips typographus are triggered mainly by an abundance of preferred hosts (i.e. weakened or freshly dead trees of Picea abies above pole stage), e.g. created by heavy storm events, in combination with favorable climatic conditions. Alpine climates limit the distribution of I. typographus, although it does occur in the foothills and valleys of the European alps. Possibly as an effect of a warming climate, the species has recently been recorded in the subalpine vegetation belt. I. typographus, prefers physiologically weakened, damaged, windthrown, recently felled or overmature trees (CFIA, 2007). In wind-felled trees, with low or no resistance at all, beetles can colonize stems at lower densities and thereby avoid the strong competition that would be likely if the colonizing beetles were trying to overcome the defensive systems of healthy trees (Eriksson, Pouttu & Roininen, 2005). In spruce forests, it normally exists in low abundance. Its population fluctuation depends on presence of suitable brood material in the stands and good weather conditions during swarming (Feicht, 2004). Infestations are more severe in stands greater than 120 years old, with preference for trees between 70 and 150 years old. Stands less than 40 years old sustain very little damage (CFIA, 2007). Suitable climatic conditions and suitable host material coincide with ports of entry or major destinations (Eglitis, 2006). The European spruce bark beetle overwinters in the adult stage, generally in the duff near the tree where it developed. A few individuals remain beneath the bark during the winter, especially in the southern part of the insect's range (Eglitis, 2006).
Eruptive outbreaks of the European spruce bark beetle result in mass attacks of living trees and may cause tree mortality at landscape-levels (Baier, Pennerstorfer & Schopf, 2007). In fact, although this beetle species prefers damaged spruce trees, the beetles also frequently kill solitary spruce trees, for example on the edges of recently harvested clear-cuts (Eriksson, Neuvonen & Roininen, 2007). Under favorable conditions and during an high population level outbreak phase, it is able to attack healthy trees and is a primary factor causing direct tree mortality. Outbreaks can develop rapidly in spruce stands that are damaged by wind, snow, stressed by drought or air pollution (Grodzki, McManus, Knizek et al, 2004). During such outbreaks, the population may increase sufficiently to start an epidemic. In an epidemic situation, spruce bark beetles can overcome the resistance of healthy trees (Joensuu, Heliövaara & Savolainen, 2008). Successful bark beetle establishment is considered to occur in two successive steps. The first step is the tree's defenses are exhausted by pioneer beetles and second, final colonization of the tree occurs (Wermelinger, 2004). The damage by this species 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. In addition, this species may cause loss of markets (domestic or foreign) due to presence and quarantine significant status (Eglitis, 2006). Adults carry a number of associated fungi such as Ceratocystis polonica. This bluestain fungus is highly virulent and can kill healthy spruce trees. In addition, this fungus stains the wood with blue streaks, which reduces its commercial value (CFIA, 2007). Attacked trees die faster than would be expected by solely phloem girdling due to larval feeding. The fungi may dry the tissue and induce tracheid aspiration or vascular plugging (Wermelinger, 2004). The organism is expected to cause significant direct environmental effects, such as extensive ecological disruption. Furthermore, the killing of a large number of trees during outbreaks causes major ecological disruptions resulting in change of tree species composition to non-host trees and increased fuel for high intensity wildfires (Eglitis, 2006). Climate warming, occuring in the past decade or so, allows the bark beetle to complete life cycles at altitudes which were previously unsuitable for its development, and thus may seriously affect the protective functions of mountain forests with regard to rockfall, avalanches and soil erosion in P. abies dominated mountain regions (Seidl, Baier, Rammer et al, 2007). The spruce bark beetle is one pest that could pose significant risk to North American forests if it were introduced. The introduction of this exotic pest could result in significant changes in forest ecosystems, such as tree species conversion, deforestation of riparian communities, increased fuel loading, and loss of biodiversity (Tkacz, 2002).
Although the European spruce bark beetle can be a very serious forest pest, it also creates new breeding material for a variety of insect species. Dead and decaying wood, including trees killed by this species, constitute a habitat for a large number of harmless species (Eriksson, Lilja & Roininen, 2006).
Global climate change is likely to affect bark beetle dynamics among other things (Joensuu, Heliövaara & Savolainen, 2008). Both its outbreak range and its outbreak intensity are likely to increase in a warming climate (e.g., Jönsson, Harding, Bärring et al, 2007, Seidl et al. 2009). In addition, climate change has the potential to weaken host defence mechanisms e.g. via increased drought and further facilitate attacks by I. typographus (e.g. Seidl et al. 2008)
Ips typographus occurs in the distribution area of the Norway spruce and is spread throughout Europe - in an area between France, northern Norway, Sweden, Finland, northern Italy, Yugoslavia, Bulgaria, Caucasus and Siberia to the province Heilungkian and northern China (Walker, 2009)
The spruce bark beetle is one of the most aggressive and serious pests of spruce in Eurasia (Bakke, 1989). The spruce bark beetle has 21 countries of origin with the top 4 being Italy, Germany, Russia and Belgium (Stephen & Gregoire, undated). In addition, the spruce bark beetle is known to be the most destructive scolytid attacking spruce forests in Palaearctic regions (Faccoli & Stergulc, 2004). Bark beetle abundance decreases with increasing latitude. Latitude is probably best seen as a fudge factor embracing several more direct correlates of population carrying capacity (Okland & Bjornstad, 2003).
Introduction pathways to new locations
Natural dispersal: Ips typographus’ range is limited by the thermal environment rather than host availability in many regions of Eurasia. Climate change could thus facilitate the colonization of higher altitude and latitude Picea abies forests by means of natural dispersal (e.g., Seidl et al. 2009).
Solid wood packing material: Ips typographus is one of the most commonly detected pests traveling on solid wood packing material, even after the adoption of the 1995 regulations intended to prevent introductions of bark-associated insects (TNC, 2005).
Transportation of habitat material: Immature stages of Ips typographus are subject to redistribution by human assisted means, especially via wood products (unprocessed logs or lumber, crating, pallets and dunnage containing bark strips) (Eglitis, 2006).
Local dispersal methods
Natural dispersal (local):
Transportation of habitat material (local): Ips typographus has demonstrated the ability for redistribution through human-assisted transport (Eglitis, 2006).
Wind dispersed: Ips typographus is capable of dispersing more than several kilometers per year through its own movement or by abiotic factors such as wind, water or vectors (Eglitis, 2006).
Ips typographus is absent from Australia but listed as a 'High Impact Pest Species' (Walker, 2009).
Preventative measures: Silvicultural measures such as favouring mixed stands over pure Picea abies stands have been reported to reduce risk for I. typographus attack (Netherer and Nopp-Mayer 2005). Prompt salvage or debarking of windthrown material may help to limit population growth, but may be impractical when large areas are involved (Eglitis, 2006). The only chance to stop mass propagation of the European spruce bark beetle is to transport infested wood out of the stands (Feicht, 2004).
Integrated management: Mass trapping of Ips typographus in combination with other measures such as removal of infested trees, have to be included in an integrated control program (Bakke, 1989). In addition, mass trapping with pheromone-baited traps or trap trees has also been successfully used to suppress beetle populations and prevent outbreak conditions (EPPO).
Chemical: Direct controls have included the use of attractant and repellent pheromones to either trap out beetles or reduce attacks on suitable host material. Insecticides have also been used in direct control, but have a number of limitations in their application (Eglitis, 2006). Work has shown that the energy reserves of this species need to be depleted before the beetles will respond to pheromones (Wermelinger, 2004). An experiment was conducted in which treatment with the I. typographus-associated fungus C. polonica enhance the capability of spruce trees to resist later beetle attacks. Thus, this experiment lends support to the hypothesis that sublethal beetle/fungus attack may trigger inducible defense mechanisms in the trees that render them more resistant to later beetle attacks (Christiansen & Krokene, 1999). In addition, experiments undergone have shown protection of spruce with anti-attractants is possible using dispensers containing a blend of verbenone and NHV. Treatments with this method decreased the probability of attack and is said to work best in conditions of clear forest edges without to-beetle-attractive wind thrown or trap trees, even in the areas with high bark beetle population (Jakus, Schlyter, Zhang et al, 2003).
Biological: The entomopathogenic fungus B. bassiana is a naturally occurring pathogen of bark beetles, especially the European spruce bark beetle. It can be used for biological control of this species in three possible ways: treatment of fallen trunks, soil treatment around spruce trees against overwintering beetles, or a combination of the fungus with the commercially available and used pheromone traps (Kreutz, Zimmermann & Vaupel, 2004a). When considering the commercial use of this fungus for biocontrol of this species of bark beetle, its efficacy at different temperatures and RH is highly relevant. In general, the optimum temperature for the growth of entomopathogenic fungi is between 20 and 30 degrees celcius, with a minimum between 0 and 10 degrees celcius and a maximum between 30 and 35 degrees celcius (Kreutz, Vaupel & Zimmermann, 2004b).
Ips typographus larvae feed in the inner bark up to 10 m along the stem of the host tree. This species prefers thicker-barked stems with a minimum bark thickness of 2.5 mm and an optimum thickness of 5.0 mm (CFIA, 2007).
The European spruce bark beetle reproduces in newly wind-felled trees (Eriksson, Pouttu & Roininen, 2005). This species has high reproductive potential (Eglitis, 2006). Males excavate a nuptial chamber and are joined by 1 to 4 females. Females construct egg galleries in the inner bark radiating outward from the nuptial chamber. Vertical egg galleries are 10 to 20 cm long and are usually three-armed, but can be two-armed or multi-branched (CFIA, 2007). Gallery length varies with gallery density, but 10-12 centimeters is an average length (Eglitis, 2006). Approximately 50 eggs are laid on each side of the egg gallery (CFIA, 2007). However, females deposit up to 80 eggs preferably on the side of the maternal gallery that least interferes with other maternal galleries (Wermelinger, 2004). Larval galleries radiate at right angles to the egg gallery and become wider as the larvae grow (CFIA, 2007). Intraspecific competition at high breeding densities affects behavior. High densities result in shorter maternal galleries and thus reduced oviposition. The optimal density is at roughly 500 maternal galleries per square meter. The sex ratio of the progeny depends on the phase of gradation. Egg production has been found to depend on temperature, with a lower temperature threshold of 11.4 degrees celcius. With nonlinear models and optimum temperature of 30.4 degrees celcius for the juvenile development and 28.9 degrees celcius for reproduction were calculated (Wermelinger, 2004). Blue-stain fungi are normally transferred with the beetle and grow into wood around the gallery. Parent females also may leave the successfully colonized host and establish another brood in other trees or logs (i.e. “sister broods”). The European spruce beetle readily infests down host material, which contains fresh cambium. Windstorms frequently provide the breeding material for subsequent outbreaks, which can kill large numbers of trees (Eglitis, 2006).
The male beetle initiates a nuptial chamber. After manifold copulation with attracted females, each female gnaws a maternal gallery with egg-pockets along the sides of the gallery. Larvae from the laid eggs gnaw right-angled to the maternal galleries larval tunnels, which end in a pupal chamber. The pupae change into hairy, brown juveniles. After maturation, grub juveniles change into dark-brown, mature adults. The whole generation development from the copulation to the adult has a duration of 7-11 weeks (Kreutz, Zimmermann & Vaupel, 2004a). Adults finish maturation in the spring prior to their dispersal flight. These flights are initiated in response to air temperatures of 20 degrees celcius. The number of generations per year is dependent upon temperature. In the northern part of its range, it has one generation a year, but it can complete two generations per year further south (Eglitis, 2006). In Central European lowlands it frequently completes two generations per year and has been reported to reach three generations in recent climatically favourable years. A first generation having a high rate of reproduction means the beginning of a large second generation, which will produce many offspring flying in the next season (Faccoli & Stergulc, 2006). The lower developmental threshold for the spruce bark beetle has been computed to be 8.3 degrees celcius. With a nonlinear model, the threshold was around 6 degrees celcius. The heat sum for total development ranged from 334 degree-days to 365 degree-days (Wermelinger, 2004).
Reviewed by: Rupert Seidl, Institute of Silviculture, Department of Forest and Soil Sciences, University of Natural Resources and Applied Life Sciences. Vienna Austria
Compiled by: National Biological Information Infrastructure (NBII) & IUCN/SSC Invasive Species Specialist Group (ISSG)
Last Modified: Monday, 27 April 2009