Hylobius albosparsus

Name:   Hylobius albosparsus
Pest Authorities:  Boheman
Taxonomic Position:  Insecta: Coleoptera: Curculionidae
Sub-specific Taxon:  
Pest Type:   Insect
Common Name(s):
   Big larch weevil (English)
   White-spotted weevil (English)
Numerical Score:  9
Relative Risk Rating:  Very High Risk
Uncertainty:   Very Uncertain
Uncertainty in this assessment results from: Uncertainty in this assessment results from the fact that insects with a similar ecological niche, such as the pales weevil, Hylobius pales, already occur in the eastern USA. The effect of interspecies competition on the ability of H. albosparsus to successfully establish itself in areas already occupied by H. pales or other indigenous species of Hylobius 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: Hylobius albosparsus would find suitable climatic conditions and hosts at many Canadian and U.S. ports of entry. This insect has a broad host range in its natural range and could probably adapt to North American hosts. Therefore, it 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 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 are capable of flying several km in search of favorable host material. Hylobius albosparsus has a potential for intercontinental spread on unprocessed logs and other wood products destined for export. If introduced, its broad host range should enable it to find suitable host material in virtually all North American conifer forests. It also has a high reproductive potential. Detection would be difficult because of its similarity in appearance to indigenous species of Hylobius. This would also increase the difficulty of eradication and plant quarantine efforts.

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: Hylobius albosparsus, like its Eurasian counterpart H. abietis, is considered a pest of conifer regeneration throughout its natural range and can have a significant effect on the success or failure of conifer plantations. However, this insect is ecologically similar to the pales weevil, H. pales, an insect native to eastern North America, which is regarded as the most serious pest of pine seedlings in the eastern USA (Nord et al. 1984). Should H. albosparsus become established in this area, it would have to compete with H. pales and other indigenous species of Hylobius for available feeding and breeding sites. Its ability to compete with indigenous species of Hylobius and cause additional seedling damage is not known.

Environmental Potential Is High Risk
The relevant criteria chosen for this organism are:  
  • Organism is expected to cause significant direct environmental effects, such as extensive ecological disruption or large scale reduction of biodiversity.
  • Introduction of the organism would likely result in control/eradication programs that may have potential adverse environmental affects.
Justification: Adult feeding by Hylobius albosparsus could alter species composition of regenerated areas in favor of non-host (broadleaf) species.

Hylobius albosparsus attacks all conifers within its natural range, but prefers species of larch, Larix spp. and pine, Pinus spp.

     This insect is widely distributed across Asia including Russia (Siberia, Transbaikalia, Russian Far East, including Kamchatka and Magadan), China, Japan, Korea and Mongolia (Pavlovskii et al. 1955, Issaev and Tarassova 1965, Issaev, 1966, Egorov 1976, Korotyaev 1977, Kondanov et al. 1979, Lindeman 1979, Egorov and Berezhnykh 1987, Liu et al. 1989, Ler 1996).
      Hylobius albosparsus is found in the northeastern portions of European Russia.
The genus Hylobius consists of several species indigenous to conifer forests of Asia, Europe and North America that are important pests of conifer seedlings. North American representatives of Hylobius include the pales weevil, H. pales, the pine root collar weevil, H. radicis, the pine root tip weevil, H. rhizophagus, the southern pine root weevil, H. alaradicis, and several other species (Drooz 1985).

Hylobius albosparsus occurs in forests up to an altitude of 1100 m (Zemkova 1965). The adult flight period usually occurs from mid-May to the beginning of September. Adult beetles often live more than 1 year, sometimes overwintering for 2 or 3 years. Young adults leave the forest litter, where they overwinter, and feed mainly on young conifer seedlings but also occasionally on branches of mature trees. They make deep wounds in the bark and can girdle seedlings and small branches. Adult feeding continues after mating and egg-laying.

Females lay eggs on the lower part of trunks, root collars and root spurs of trees and freshly cut stumps. This insect can attack dying trees and trees stressed by forest defoliators, such as Dendrolimus sibiricus, Zeiraphera diniana, and others or trees damaged by forest fires. Each female lays between 60 to 100 eggs.

Larvae hatch after 2 to 3 weeks and construct vertical galleries, filled with frass, in the phloem and, later, in the sapwood. In thin roots, a gallery may extend to 1.5 m. Larvae overwinter in galleries and in the following spring, they resume feeding and gallery construction.

Larvae construct oval chambers in the wood for pupation sites. Normally, pupation takes place in these chambers in June or July. Young beetles appear in August and overwinter in the forest litter. The developmental cycle of H. albosparsus requires 2 years. Sometimes, however, larvae overwinter for a second time and the developmental cycle takes 3 years. Populations are mixed and it is possible to see beetles of different generations at the same time (Rozhkov et al. 1966, Egorov and Berezhnykh 1987, Vorontsov 1995).

Economic Impact:    Hylobius albosparsus is one of several important pests of conifers in the region of its present distribution. Breeding attacks occur in stressed, dying or cut trees of different ages and/or fresh stumps. On living trees, larvae usually feed in the bark and do not destroy the phloem. On dead trees and stumps, they feed mainly in the phloem and wood. The larvae usually do not cause serious losses in healthy forests. Nevertheless, they may cause some decrease of wood and seed production as well as reduction in wood marketability. The most severe damage from larval feeding is usually observed in coniferous forests previously attacked by forest defoliators such as Dendrolimus sibiricus, Zeiraphera diniana and others or trees damaged by forest fires

The primary damage caused by Hylobius albosparsus is adult feeding on seedlings and young trees less than 10 years old. Adults feed on the bark of young plants and branches and often girdle and kill seedlings. In the northern forest steppe zone, adult weevils, both H. albosparsus and H. abietis prefer to feed separately on young, isolated trees or trees on the edge of stands under an open canopy of Pinus sylvestris. They avoid conifer regeneration in dense stands. In the southern Tiaga, adults are abundant in cutover areas where they feed on clumps of young regeneration. In fresh clearcuts, up to 100% of the seedlings may be damaged. Intensity of damage declines sharply with the distance from the clearcut. Heavy adult feeding can result in plantation failure. (Pavlovskii and Shtakelberg, 1955, Issaev 1966, Rozhkov et al., 1966, Bogdanova 1976, Kondanov et al. 1979, Egorov and Berezhnykh 1987, Liu et al., 1989, Vorontsov 1995, Ler 1996, Gourov 2000).

Environmental Impact:   Because it mainly affects seedlings of host plants, this insect is a serious pest of plantations and natural regeneration. This can alter the composition of tree species in regenerated areas in favor of non-host broadleaf species.

Control:    Government sponsored and funded pest management programs are conduced in areas where Hylobius albosparsus causes damage. Pest management measures include survey, silvicultural and sanitary measures designed to improve forest vigor and reduce susceptibility of trees to attack. In addition, infested trees and stumps are removed and infestations are treated with insecticides. Young plantations are protected by trenches designed to trap adult beetles.

Symptoms:    Symptoms of infestation include the presence of larval galleries in fresh stumps or weakened and dying trees. Seedling mortality in young conifer regeneration and feeding injury on tender stems is evidence of adult feeding.

Morphology:    The larvae are up to 24 mm long and white or yellowish-white in color. The head is orange-red or light chestnut-red, 3.3 mm long with dark brown, with double-toothed mandibles. There is a dark longitudinal line on the top of the frons.

The pupae are yellowish-white and up to 18 mm long. On the frons, there is a pair of nipple-shaped outgrowths, each with a distinct projection. On the rostrum, there are 4 pairs of small projections. On the pronotum, small projections are distributed as follows: two pairs on the front border of the pronotum, two pairs on the back border, three on each lateral border, two pairs on the middle. These thorn-shaped outgrowths are well developed on the tergites of the abdomen, especially on 5th-7th segments. The end of the abdomen has two long and thin outgrowths.

Adults are 11-16 mm long, and has the typical morphology for beetles of the genus Hylobius (e.g. H. abietis). The body is light brown, dark brown or black, covered with white or yellowish hair-shaped scales. Young adults are are light colored and darken with age. The rostrum is covered by deep points and has no well-developed longitudinal keel. The first segment of the antennal club is equal in length to the second segment or is shorter then it. The prothorax is much narrower than the base of the elytra and has rounded borders and a short bright longitudinal keel with cavities from both sides along it. The front of the prothorax is covered with small points. On the middle and back parts of prothorax, the points are larger and sometimes interflow between them. The scutellum is smooth with small weak points. The elytra have parallel borders or are a little narrowed at the base. Their length is not more than twice their common width. Rows of points on the elytra are deep and intervals between rows are a little wider than rows. White or yellowish hair-shaped scales on the elytra are concentrated into distinct spots located between rows of points. There are hair-shaped scales between the spots (Rozhkov et al. 1966, Mozolevskaya et al. 1991).

Testing Methods for Identification:    Examination of adults by a taxonomist with expertise in the family Curculioidae is required for positive identification. The adults have sufficient characteristics to permit entomologists to make field identifications at least to genus.

Adults are strong fliers and can travel considerable distances to find suitable host material.

Breeding in stumps and root systems of recently cut conifers poses no possibility of transporting the immature life stages via international trade. However, logs harvested from dying or weakened trees could contain weevil brood and there is a possibility that adult weevils could hitchhike on conifer logs or other wood products.

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Drooz, A.T. 1985. Insects of eastern forests. USDA Forest Service, Miscellaneous Publication 1426, 608 pp.
Egorov, A. B. 1976. Review of the fauna of weevil beetles (Coleoptera, Curculionidae) of Primorie Territory. Entomologicheskoe Obozrenie 55:(4): 826 - 841 (in Russian).
Egorov, A. B.; Berezhnykh, E. D. 1987. Fauna of weevil beetles (Coleoptera, Curculionidae) of Western and central parts of Baikal - Amur Magistral. In: Insects of the Zone of Baikal - Amur Magistral. Nauka, pp. 29 - 40 (in Russian).
Gourov, A.V. 2000. Hylobius species (Coleoptera: Curculioidae) from Siberia and the distribution patterns of adults in Scots pine stands. Entomologica Fennica 11: 57-66
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Issaev, A. S.; Tarassova, D. A. 1965. Borer pests of pine in Central Amur river basin. Study of Siberian Forests Protection. Moscow: Nauka, pp. 5 - 19 (in Russian).
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Ler, P. A. 1996. Taxonomic keys for insects of Russian Far East. V. III, part 3, Beetles. 1996, Vladivostok: Dal’nauka, 556 pp. (in Russian).
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Mozolevskaya, E. G.; Belova, N. K.; Lebedeva, G. S. 1991. Practical manual on forest entomology. Manual for Universities, 3rd edition. Moscow: Ecologia, 256 pp. (in Russian).
Nord, J.C.; Ragenovich, I.; Doggett, C.A., 1984. Pales weevil. USDA Forest Service, Forest Insect and Disease Leaflet 104, 11 pp.
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Rozhkov, A. S.; Raigorodskaya, I. A.; Byalaya, I. V. 1966. Pests of Siberian larch. Moscow: Nauka, 320 pp. (in Russian).
Vorontsov, A. I. 1995. Forest entomology: Manual for universities. 5th edition. Moscow: Ecologia, 352 pp. (in Russian).
Zemkova, R. I. 1965. Biology and economical importance of borer pests of Siberian pine in Western Sayan. In: Study of Siberian Forests Protection. Moscow: Nauka, pp. 20-50 (in Russian).
Andrei Dorian Orlinski
T.V. Bassova 
Name and Address of the First Author:
Andrei Dorian Orlinski
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CREATION DATE:        05/03/02