Taxonomic name: Hylastes ater (Paykull)
Synonyms: Hylastes angusticollis Eggers, Hylastes pinicola Bedel, Hylesinus chloropus Duftschmidt, Ipsocossonus anomalus Oke 1934
Common names: bark beetle, black pine bark beetle, exotic bark beetle
Organism type: insect
Hylastes ater is considered a pest in many regions due to the damage that it causes to trees, specifically pine species. Although this species is native to Europe, it has recently been declared a pest there. In addition, the introduction of the species into other countries, usually by accidental means, has become an issue primarily due to the damage it causes to the species, Pinus radiata, which affects aspects of the economy as well as ecosystems. H. ater is a widespread species that could continue to cause problems if not properly inspected and managed.
Hylastes ater adults are cylindrical in form and are slate gray or shiny black in color. They have reddish-brown antennae and legs (CFIA, 2008). The elytra are coarsely punctate-striate, whereas the prothorax is finely punctate except for a conspicuous impunctate median ridge. The frons is marked with dense punctures (Walker, 2008). H. ater range in size from 3.5 to 5.5 mm long and 1.4 mm wide when they are adults. Viewed from above, H. ater has a small portion of head that projects beyond the pronotum. The head is projected downward and is prolonged into a short rostrum (CFIA, 2008). Eggs are pearly white in color, less than 1 mm long and about 0.4 mm wide with rounded ends and nearly parallel sides. The larvae are white, c-shaped, legless grubs with an amber colored head capsule. Pupae are also white, mummy-like, and they have some adult features which include wings that are folded behind the abdomen (Pasek, 2000). Newly emerged beetles are uniformly reddish-brown in color, but as they mature their color darkens. The elytra is the last to darken (Walker, 2008). In addition, adults are strong fliers (Pasek, 2000).
Please follow this link for diagnostic images of Black pine bark beetle Hylastes ater (Paykull) (Coleoptera: Curculionidae: Scolytinae: Hylesinini: Hylastina) (Walker 2008)
natural forests, planted forests
Hylastes ater primarily inhabit stumps and roots of felled pine trees or logs if they remain on site, and this species keeps close contact to the soil (Reay, Thwaites & Farrell, 2005). Experiments have shown that H. ater clearly prefer pine species when no choice could be made between alternative hosts. Although this species prefers species of pine as a host, results from experiments conducted in New Zealand on Pinus radiata plantations suggest that no adaptation is required by H. ater to convert to a non-native host (Leahy, Oliver, Leather et al, 2007). Host volatiles aid in the selection of the host. It has actually been shown that volatiles are the most powerful orientation cues for H. ater (Reay & Walsh, 2002a).
Hylastes ater is considered a pest in most areas that it inhabits. It is an important threat to the biosecurity of all forested countries (Brokerhoff, Jones, Kimberly et al, 2006). The reasons for its threatening status are due to the sapstain and other damaging fungi that it can vector (Glare, Reay, Nelson et al, 2008). H. ater vectors microorganisms that block the host's defenses, which causes a reduction of cellulose and pectin or produces large masses of fungal hyphai. It is easy for staining fungus to enter through the galleries that are created by H. ater (Lanfranco, Peredo & Ide, 2004). Most damage to hosts is actually caused by the female H. ater during ovarial maturation when they feed on root collars and tap roots of healthy pine seedlings (Mausel, Gara, Lanfranco et al, 2007). As a result of the damage they cause to hosts, ecosystems are negatively affected due to the sometimes fatal effects of H. ater, which in turn causes harm to economies that rely on the exportation of lumber (Lanfranco, Peredo & Ide, 2004). Another secondary effect includes human health issues. Human health may be affected by the use of pesticides, fumigants and preservatives needed to treat wood articles where this species has become established. H. ater has a high reproductive potential and is capable of dispersing more than several kilometers per year through either by means of its own movement or by abiotic factors, but also by human-assisted transport caused by growing international trade and tourism (Pasek, 2000).
Although Hylastes ater is considered a pest in most of the regions in which it inhabits, it could be considered useful in certain regions. Exotic tree plantations have been established in regions for their economic and ecological benefits. Among these trees, Pinus radiata is one exotic species commonly planted, specifically in tropical regions and regions in the Southern Hemisphere. Aside from benefits, this species can also develop into a serious invasive weed that can damage native ecosystems. Pinus radiata is a preferable host to H. ater in these areas and thus, this species of beetle, being a seedling-invading pest as well as a vector of pathogens, could reduce the invasiveness of Pinus radiata as well as other exotic tree species (Wingfield, Slippers, Roux et al, 2001).
It is rare that Hylastes ater actually kills trees, but it is considered to be a secondary pest because of its power to vector plant-pathogenic and lumber-degrading fungi (Mausel, Gara, Lanfranco,et al, 2007). In addition, experiments have shown that young, healthy seedlings survive attacks by H. ater (Zondag, 1982).
Native range: Hylastes ater is native to Europe and parts of Asia, which include China and the Republic of Korea. This species is widely dispersed in these regions.
Known introduced range: In addition, it has been introduced to many other regions of the world including Australia, New Zealand, North America, parts of Central and South America, and South Africa (SCION, 2001). H. ater is established wherever exotic pine forests occur in these regions (Reay & Walsh, 2001b).
Introduction pathways to new locations
Forestry: Exportation of lumber has caused the spread of Hylastes ater (Lanfranco, Peredo & Ide, 2004).
Natural dispersal: Adults easily fly to new locations. Wind can assist swarming adults to distant and further locations (M. Knížek, pers. comm.)
Local dispersal methods
Natural dispersal (local): Adults easily fly to new locations, mainly if suitable and attractive material for their nutrition and reproduction needs are present (M. Knížek, pers. comm.).
Wind dispersed: Adults easily fly to new locations. Wind can assist swarming adults to distant and further locations (M. Knížek, pers. comm.)
Early detection of new establishments of Hylastes ater is the most important step towards management (Brokerhoff, Jones, Kimberly, Suckling & Donaldson, 2006). Once the species has been discovered, there are different methods of eradication that have been practiced.
Chemical: Raw terpentine and ethanol have been recommended for use in trapping programs for H. ater (Reay & Walsh, 2002a). In addition, the pesticide, carbosulfan, was tested on Pinus radiata seedlings in New Zealand to see if it would affect the amount of damage caused by H. ater, and the results concluded that this pesticide provided significant protection to the pine seedlings from H. ater (Reay & Walsh, 2002b). Dipping bare rooted seedlings in slurry containing a pesticide even before planting may reduce the mortality of seedlings (Pasek, 2000).
Physical: Some known predators of H. ater are species of Rhizophagus beetles, and they are a possiblity for introduction and establishment for natural means of eradication of H. ater (SCION, 2001).
Adults feed on young bark of freshly-planted seedlings after emergence. Hylastes ater feeds from the collar downwards of the root and always underneath the bark (Leahy, Oliver, Leather et al, 2007). Immature beetles feed on the inner bark of pine, spruce, true firs, Douglas-fir, and larch seedlings (CFIA, 2008)
Breeding occurs primarily in the inner bark of roots, stumps, and base of trees that are either dead or dying. The brood galleries consist of a short entrance tunnel that leads to an oblique nuptial chamber. Females are responsible for the boring of a uniramous gallery, which is typically between 8 and 13 cm in length. This gallery is usually parallel with grain of the wood. Males are responsible for the clearing of the debris from the central egg gallery. The egg galleries reach the surface of the sapwood (CFIA, 2008). Adults have been observed copulating before the emergence of eggs, and sometimes the female leaves her first brood gallery to start another one, which indicates that mating had occurred in these instances before initiating the nest (SCION, 2001).
In total, about 100 eggs are laid in their own individual niches along the walls of the egg gallery. Larval galleries start out at right angles to the egg galleries, but over time they become random and eventually obliterate both the early larval galleries and those made by the parents (CFIA, 2008). Larvae development typically takes approximately 8 to 10 weeks (Leahy, Oliver, Leather et al, 2007). However, larvae may take up to 18 months to develop into maturity (Glare, Reay, Nelson et al, 2008). When the brood matures, there are groups of about 40, but could get up to 120 beetles that may be present in broad irregularly shaped communal galleries that are underneath the bark (CFIA, 2008). There are four stages of growth, which the larvae passes through in becoming an adult. The last stage lasts the longest amount of time, however, the rate of growth tends to depend on seasonal temperatures. Once the larvae is fully grown, they pupate. This pupal stage lasts about 6-14 days (SCION, 2001).
Reviewed by: Ing. Milos Knizek, Ph.D. Forestry and Game Management Research Institute, Czechia
Compiled by: National Biological Information Infrastructure (NBII) & IUCN/SSC Invasive Species Specialist Group (ISSG)
Last Modified: Monday, 6 September 2010