Pityogenes spessivtsevi

Name:   Pityogenes spessivtsevi
Pest Authorities:  Lebedev
Taxonomic Position:  Insecta: Coleoptera: Scolytidae
Sub-specific Taxon:  
Pest Type:   Insect
Common Name(s):
   Spessivtsev’s engraver (English)
   Spiral bark beetle (English)
   Spiral engraver (English)
   Spiral-gallery engraver (English)
   Spruce engraver (English)
   Ips spessivtsevi (Lebedev)
   Pityogenes perfosus Beeson
Numerical Score:  6
Relative Risk Rating:  High Risk
Uncertainty:   Very Uncertain
Uncertainty in this assessment results from: The ability of Pityogenes spessivtsevi to adapt to North American conifers, become an aggressive tree killer, or compete successfully with the complex of North American spruce infesting Scolytidae is not known.

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 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 and host material, spruce, would be available at ports of entry in the northern U.S. and Canada. This insect has an active, directed searching capability and, provided it can adapt to North American spruces, would have a high likelihood of reproducing after entry.

Spread Potential Is High Risk
The relevant criteria chosen for this organism are:  
  • Organism is capable of dispersing more than several km per year through its own movement or by abiotic factors (such as wind, water or vectors).
  • 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.
  • Eradication techniques are unknown, infeasible, or expected to be ineffective.
  • Organism has broad host range.
Justification: Adults can fly short distances in search of suitable breeding sites and are also subject to wind dispersal. Other species of Pityogenes have been intercepted at North American ports of entry. This suggests that Pityogenes spessivtsevi could also be transported via logs or wood products containing bark strips. This insect has a high reproductive potential and potential hosts have contiguous distributions, especially in boreal forests. Newly established populations could be confused with indigenous bark beetles, thus making detection difficult. Moreover, the immature stages are cryptic and difficult to detect. These factors would also make eradication difficult.

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.
  • Organism directly causes tree mortality or predisposes host to mortality by other organisms.
  • Organism may cause loss of markets (domestic or foreign) due to presence and quarantine significant status.
Justification: Most bark beetles of the genus Pityogenes prefer to attack weakened, dying or freshly cut trees and are typically associated with more aggressive bark beetles as secondary invaders. The ability of Pityogenes spessivtsevi to become an aggressive, tree-killing insect in North America is unknown. Quarantine measures may affect flow of coniferous wood products, with a potential to increase prices of wood products and create local shortages.

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: Pityogenes spessivtsevi is one of a large complex of insects instrumental in the decomposition of dead wood. If it assumes this role in North America, environmental impacts would be minimal. However, this insect has the potential to attack living trees and alter tree species composition in North American forests.

Pityogenes spessivtsevi attacks spruce, Picea spp. including Picea schrenkiana (=P. tianschanica = P. prostrata = P. robertii) (Stark 1952, Kostin 1955, Pavlovskii and Shtakelberg 1955, Makhnovskii 1966, Maslov 1988), Picea smithiana (=Picea morinda), Picea abies (=Picea excelsa). Two species of pines, Pinus spp., Pinus gerardiana and Pinus roxburghii are also reported hosts (Wood and Bright 1992).

      This insect is found in three Central Asian countries: Kazakhstan, Kyrgyzstan and Tajikistan (Parfentiev 1951, Stark 1952, Kostin 1955, Pavlovskii and Shtakelberg 1955, Makhnovskii 1966). It is also reported from China (Xinjiang Province), India (Uttar Pradesh, Kashmir), and Asian Russia (Wood and Bright 1992).
Nineteen species of bark beetles of the genus Pityogenes are found in Asia, Europe and North America (Browne 1968, Wood 1982). Seven species are indigenous to North America and all infest pines, Pinus spp., (Drooz 1985, Furniss and Carolin 1977, Wood 1982). They are usually of secondary importance and attack the tops and limbs of weakened, dying and freshly cut trees. Under favorable conditions they may develop into sufficiently large numbers to attack and kill small trees.

The number of generations of Pityogenes spessivtsevi varies with elevation. It has one generation a year at high elevations, between 2200-3200 m. At elevations ranging between 1500 and 2200 m, it can complete 1.5-2 generations and between 1200 and 1400 m, it completes two generations per year. Adults are the primary overwintering stage although some larvae and pupae may also overwinter.

Overwintering adults become active in spring. Beetles begin maturation feeding in the cambium layer near where they pupated after constructing emergence holes and leaving their pupal cells. Flight, mating and oviposition adults occurs from early May to late June. The number of emergence holes is usually less than the number of emerging beetles because some adults emerge through holes made by other adults. At low elevations (1200-1400 m), oviposition of the first generation adults occurs in early August and the second-generation brood adults appear in October.

As is typical of the genus Pityogenes, P. spessivtsevi prefers to attack the thin barked portions of host trees. This insect often attacks trees also attacked by Ips hauseri (Coleoptera: Scolytidae). I. hauseri prefers to attack thicker barked portions of the same trees (Parfentiev 1951, Makhnovskii 1966, Maslov 1988).

Pityogenes spessivtsevi is polygamous. Males initiate attacks and are soon joined by three to six females. Mating takes place in a nuptial chamber in the cambium. After mating, each female constructs an egg gallery from the nuptial chamber and extend spirally in two directions. Female galleries may reach 5-7 cm in length. Eggs are laid individually in niches made by the female in the external (prominent) side of the egg gallery. On smaller branches, not all female galleries have a spiral form. Under these conditions, eggs are laid on both sides of the gallery. Larval galleries are short, usually 2-3 cm long and becoming progressively wider as the larvae increase in size. Pupal cells are located at the end of the larval galleries. The galleries engrave both the sapwood and bark (Parfentiev 1951, Makhnovskii, 1966, Maslov 1988).

Economic Impact:    Pityogenes spessivtsevi is considered an important pest of Picea schrenkiana in Central Asia. It can attack slightly stressed and healthy trees of different ages and continues to breed in the same trees over several consecutive years, ultimately causing their death. Infestations of this bark beetle are commonly associated with the engraver beetle, Ips hauseri, and Pityophthorus kirgisicus (Coleoptera: Scolytidae). Woodborers associated with these bark beetle attacks include Tetropium staudingeri, Dokhtouroffia nebulosa and Dokhtouroffia baeckmanni (Coleoptera: Cerambycidae). The typical sequence of invasion is not clear, however, although many workers consider Ips hauseri to be the more aggressive bark beetle. However, P. spessivtsevi is more common than Ips hauseri in high elevation spruce forests (Parfentiev, 1951, Marikovskii 1956, Makhnovskii 1966, Maslov 1988).

Environmental Impact:   Extensive tree mortality caused by bark beetles in high elevation forests with steep slopes could accelerate soil erosion and reduce water quality. Moreover, infestations and resultant tree mortality could result in changes of tree species composition in natural forests in favor of non-host species. Large numbers of bark beetle killed trees will increase fuel levels in forests and increase the severity and extent of wildfires.

Control:    Control measures include rapid removal and processing of infested trees and silvicultural measures, such as thinning, to maintain tree vigor. Planting of conifers on unsuitable sites should also be avoided.

Eradication would consist of destruction of infested trees and establishment of quarantine zones designed to regulate movement of infested material.

Symptoms:    Symptoms of bark beetle infestation include the occurrence of host trees with all or a portion of the tree containing faded or yellow foliage. The bark surface will contain pitch tubes and/or reddish colored boring dust and, if the beetles have emerged, small exit holes. Egg and larval galleries, characteristic of Pityogenes spp. are present in the cambium and inner bark of infested trees.

Morphology:    Adult bark beetles of the genus Pityogenes are 1.5-3.5 mm in length, red brown to dark brown in color and superficially resemble the closely related Ips engraver beetles, Ips spp. The head is not visible when viewed dorsally. The females of most species have conspicuous cavities in the front of their heads. The elytral declivity is concave and armed with a series of spines on the margin. The declivital spines are more pronounced on males than females (Drooz 1985, Furniss and Carolin 1977, Grüne 1979).

Eggs are rounded and pearly white in color. The larvae are white, ‘C’-shaped grubs with an amber colored head capsule. Mature larvae are about 5-6 mm long. The pupae are white, mummy-like, and have some adult features, including wings that are folded behind the abdomen. The immature stages of bark beetles generally lack sufficient characteristics to facilitate species identification.

Testing Methods for Identification:    Examination of adults by a specialist in the family Scolytidae) is required for positive identification.

Adults are capable of flying short distance in search of suitable host material. They are also subject to wind dispersal. Immature stages (larvae and pupae) and adults can be transported in unprocessed logs, wood products or wooden packing material, dunnage or pallets containing bark strips. Pityogenes spp. are frequently intercepted at U.S. ports of entry. The most commonly intercepted to date is a spruce infesting European species, P. chalcographus (Haack 2001 press).

Browne, F.G. 1968. Pests and diseases of forest plantation trees. Clarendon Press, Oxford, U.K. 1330 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 1339, 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 U.S. ports of entry: 1995-2000. Integrated Pest Management Reviews 6(3): 253-282
Kostin, I. A. 1955. Insect pests of coniferous forests of Picea schrenkiana in Ala-Tau of Djungar, Zailiisk and Kungei. Proceedings of the Institute of Zoology of the Academy of Sciences of Kazakh SSR IV: 36-45 (in Russian).
Makhnovskii, I. K. 1966. Spruce engraver, or Spiral-gallery engraver - Pityogenes perfosus Bees. In: Pests of Mountain Forests and their Control. Moscow: Lesnaya Promyshlennost, pp. 52-53 (in Russian).
Makhnovskii, I.K. 1960. Pests of spruce-fir forests of Chatkal' and Fergan Mountain ridges. Tashkent: Edition of Academy of Agricultural Sciences of Uzbekistan, 49 pp. (in Russian).
Marikovskii, P. I. 1956. Inter-specific relations of bark beetles living on Picea schrenkiana. In: Proceedings of the Institute of Zoology and Parasitology. Frunze: Edition of the Academy of Sciences of Kyrgyz SSR 5: 132 - 141 (in Russian).
Maslov, A. D. 1988. Guide on forest protection against pests and diseases. Moscow: Agropromizdat, 414 pp. (in Russian).
Parfentiev, V. Ya. 1951. Bark beetles and longhorn beetles of Picea schrenkiana. Entomologicheskoe Obozrenie 31: 428 - 434 (in Russian).
Pavlovskii, E. N.; Shtakelberg, A. A. (Editors) 1955. Forest pests guide. Moscow-Leningrad: Edition of Academy of Sciences of the USSR 2: 422 - 1097 (in Russian).
Stark, V. N. 1952. Fauna of the USSR; Coleopterous insects, V. XXXI: Bark beetles. Moscow-Leningrad: Edition of the Academy of Sciences of the USSR, 534 pp. (in Russian).
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.
Andrei Dorian Orlinski
T.V. Bassova 
Name and Address of the First Author:
Andrei Dorian Orlinski
1, rue Le Nôtre
France 75016
CREATION DATE:        05/15/02
MODIFICATION DATE:        05/06/04