Monochamus impluviatus

Name:   Monochamus impluviatus
Pest Authorities:  Motschulsky
Taxonomic Position:  Insecta: Coleoptera: Cerambycidae
Sub-specific Taxon:  
Pest Type:   Insect
Common Name(s):
   Siberian speckled sawyer (English)
Numerical Score:  6
Relative Risk Rating:  High Risk
Uncertainty:   Very Uncertain
Uncertainty in this assessment results from: The uncertainty concerns the ability of Monochamus impluviatus to become an aggressive tree killer in North American forests and compete successfully with indigenous woodborers including species of Monochamus. Moreover, the interrelation between this insect and Asian species of pinewood nematodes, Bursaphelenchus spp., and their possible pathogencity to North American conifers is unknown.

Establishment Potential Is Moderate 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 high inoculum potential or high likelihood of reproducing after entry.
Justification: Suitable climatic conditions and hosts occur at ports of entry in Canada and the northern U.S. This insect is expected to have a high reproductive potential and a high likelihood of survival should it be introduced.

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: Adult Monochamus are strong fliers and capable of traveling over 2-3 km in search of suitable host material. This genus of insects has demonstrated ability for human assisted transport. Records from USDA APHIS indicate that between 1985 and 1998, insects believed to be Monochamus spp. were intercepted on over 250 occasions in U.S. ports of entry. M. impluviatus has a broad host range and potential hosts (conifers) have contiguous distributions across many regions of North America. Newly established populations may go undetected due to their cryptic nature and the fact that adults, at least superficially, resemble indigenous species of Monochamus. Therefore, eradication is expected to be difficult.

Economic Potential Is High 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.
  • 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.
  • No effective control measure exists.
  • Organism has potential to be a more efficient vector of a native or introduced pest.
Justification: If introduced and established, Monochamus impluviatus can be expected to cause the same injury that is already being caused by native species of Monochamus, primarily loss of structural integrity and quality of harvested timber. Since native North American conifers are not damaged by the pinewood nematode, Bursaphelenchus xylophilus, which is native to North America and several native North American species of Monochamus have already been determined to be vectors of this pathogen, little additional damage is expected from its introduction and establishment unless it becomes an aggressive tree killer as reported by some workers in its natural range. Moreover, should an introduction of M. impluviatus be accompanied by an introduction of one or more species of Bursaphelenchus indigenous to Asia, resultant impact could be severe.

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: If introduced and established, and assuming that Monochamus impluviatus would behave in the same manner as indigenous species of Monochamus, it would be another of a complex of insects involved in the decomposition of dead conifers.

Monochamus impluviatus attacks all conifers present in its natural range including species of larch, Larix spp., pine, Pinus spp., spruce, Picea spp., fir, Abies spp and others. Preferred hosts are larch and Siberian pine, Pinus sibirica (Florov 1951, Plavilshchikov 1958, Issaev and Tarassova 1965, Issaev 1966, Cherepanov 1983, Mamaev 1985).

     This insect occurs across Asian Russia, including all of Siberia, Transbaikalia and the Russian Far East. It is also found in China, Korea and Mongolia (Pavlovskii and Shtakelberg 1955, Plavilshchikov 1958, Ivliev and Kononov 1966, Averenski 1971, Lindeman 1979, Cherepanov 1983, Mamaev 1985, Vorontsov 1995).
      Monochamus impluviatus is found in the northern and central portions of European Russia.
Monochamus is a large genus of woodboring insects. In temperate climates they attack various species of conifers in the forests of Asia, Europe and North America. Several species are pests of tropical broadleaf trees in Africa (Browne 1968). Species indigenous to North America include M. caroliniensis, M. marmorator, M. notatus, M. titillator and M. scutellatus.

Adult flight of Monochamus impluviatus occurs in May and June, earlier that any other known temperate forest species of this genus. In Yakutia and other areas in extreme northern Russia, adult flight begins in June. Adults prefer to fly during sunny days in wide-open spaces such as large felled areas of conifers. As soon as flight begins, adults begin maturation feeding on needles and bark of tender branches of young larch and pine trees. Later they feed, on the bark of branches of mature trees. Maturation feeding usually lasts for 12-15 days.

After the onset of maturation feeding, females begin to lay eggs. Beetles continue to fly and lay eggs in July. Between one and three eggs are laid in incisions 3-4 mm wide made by the female in the bark of the mid and upper boles of host trees. Eggs may also be deposited in the thick bark of large branches.

Embryonic development usually takes 10-27 days. Young larvae feed first in the bark, phloem and sapwood making long irregular galleries filled with frass. Between 20-25 days after egg hatch, the larvae enter the wood and construct a gallery 3-15 cm long and 0.5-2.0 cm wide. The first part of the gallery has a horizontal orientation, then turns upwards and returns to the wood near the bark surface in the general vicinity of the entrance hole. As a result, the exit hole is typically situated about 1.5-2 cm above the entrance hole. The larvae overwinter in the gallery. In spring, they extend the gallery slightly and prepare a cell for pupation at a depth of 2-3 mm from the bark. The pupal cell is 21-28 mm long and 6-8 mm wide. The head of the pupa is pointed oriented toward the bark. Pupal development requires 25-32 days in May and 7-13 days in June. Emergence holes are round and 5-6 mm in diameter.

According to some scientists, the development cycle of Monochamus impluviatus normally takes one year. In mountainous areas above elevations of 1000 m, 2 years are required to complete development (Florov 1951, Pavlovskii and Shtakelberg 1955, Plavilshchikov 1958). According to other workers, the developmental cycle normally takes two years with the first overwintering occurring during an early larval instar under the bark and during the second overwintering occurring deep in the wood (Rozhkov et al 1966, Cherepanov 1983).

Economic Impact:    Opinions about the economic importance of Monochamus impluviatus are divided. According to many workers this species of Monochamus is considered to be the most likely to attack healthy or slightly stressed trees. It may also attack dying and cut trees (harvested not more than one year) (Florov 1951, Plavilshchikov 1958, Rozhkov et al. 1966, Cherepanov, 1983). They consider M. impluviatus to be one of the most important and frequent pests of larch, Siberian pine, and other conifers within its natural range. This insect is commonly associated with trees defoliated by the Siberian silk moth, Dendrolimus sibiricus, other forest defoliators or forest fires. It occurs under a wide range of forest conditions (Florov 1951, Zemkova 1965, Ivliev and Kononov 1966, Averenski 1971, Krivosheina and Kompantsev 1987). Larval galleries cause reduction of the structural integrity and quality of wood.

Other scientists, however, believe Monochamus impluviatus to be of minor economic importance because it is not abundant or widespread (Plavilshchikov 1958, Issaev 1966, Rozhkov et al.1966, Kondakov et al. 1979). This difference of opinion may be due to regional differences in its abundance and behavior.

Monochamus impluviatus has not yet been implicated as a vector of wood infesting nematodes of the genus Bursaphelenchus, as have other species of Monochamus. However, it is considered a potential vector (Kulinich and Orlinskii 1998).

Environmental Impact:   In areas where Monochamus impluviatus is a tree killer, it could alter tree species composition of forests in favor of non-host species. Moreover, increased levels of tree mortality could result in higher risk and increased intensity of wildfires.

Control:    Control measures include silvicultural techniques designed to increase resistance of forests to attack, cutting and processing of infested trees and insecticide treatments (Rozhkov 1966, Vorontsov 1995).

Symptoms:    Infested trees contain narrow slits in the bark, indicative of oviposition sites, boring tunnels filled with frass that superficially resembles straw or coarse wood shavings and adult exit holes that are round to slightly oval.

Adult maturation feeding consists of removal of the bark from shoots of host trees. These eventually die leaving dead tips on the trees.

These symptoms are not specific to Monochamus impluviatus, however. They are characteristic of most species of Monochamus as well as other woodborers of the family Cerambycidae.

Morphology:    The egg is white, elongated, slightly curved and rounded at both ends. Dimensions are 3.1 mm long, and 1.0 mm wide. The chorion is a matte silver color and is covered by small cells (Cherepanov 1983).

The larva is yellowish-white in color, without legs and 17-23 mm long when mature. It may be distinguished from other Monochamus larvae by a number of characteristics including the distribution of hairs on the front border of the pronotum, the presence of a depression on the epistoma and the shape of the front corners of the pronotum. The head is brown, up to 3.2 mm wide, slightly narrowed in the front and half retracted into the prothorax. The epistoma is orange in the front half and white in the back half. The antennae are short, orange brown. The mandibles are black. The width of the pronotum is twice as long as its length. The pronotum is yellow and narrowed in the front part. The basisternum is sclerotised on the front border and has reddish hairs on the lateral sides. The meso and metasternum have multiple granules in the middle forming two transverse rows separated by a fissure. The abdomen is yellowish-white, with reddish hairs on the lateral sides. Dorsal ambulatory warts (ampullae) are prominent with white granules forming four transverse rows and one curved row from each lateral side. A spot of five granules is situated between the lateral curved row and the transverse rows. Ventral ampullae are separated by transverse fissure. One or two transverse rows of granules are situated on the front side of the fissure, and one transverse row of granules is situated on the backside of the fissure. The weight of mature larvae ranges from 140-301 mg (Florov 1951, Rozhkov et al. 1966, Cherepanov 1983).

The pupa is white, 15-20 mm long and 4.5-6.0 mm wide. It is easily recognized by the distribution of small thorns on the frons and short antennae curved in rings. The head is large with a longitudinal fissure with curved rows of small acute thorns on each side in the front part of the antennae. A transverse row of six bristles is situated on the front border of the frons. The pronotum is transverse and prominent. The femurs have a transverse row of small acute thorns at the top. The abdomen is wide at the third and fourth segments and then narrows toward the back, with a longitudinal fissure on the dorsal side. Tergites have 2-3 transverse rows of small acute thorns on the back part and on each side of the fissure. These thorns form narrow transverse stripes. The top of the abdomen has a conic urogomphal outgrowth, which finishes with a sclerotised thorn. The weight of the pupa is ranges from126-274 mg (Florov 1951, Rozhkov et al. 1966, Cherepanov 1983).

The adult is blackish in color and 11-20 mm long. It is easily distinguished from other species of Monochamus by the well-developed sharp punctuation at the base of elytra, the presence of speckles formed by small gray hairs on the elytra, rather thick antennae, and short elytra. The head is rounded and widely punctuated at the posterior border. The vertex has a depression and a round yellow spot. The frons is prominent, covered by gray hairs and has a small punctuation and a central longitudinal fissure. The eyes are sharply facetted. The pronotum is transverse, with a conic lateral prominence on each side, with wide irregular punctuation and irregular ochre and gray hairs forming four round spots on the back part. The scutellum is triangular and short, covered by yellowish and gray hairs, with a longitudinal stripe. The length of the elytra is two to three times longer than their width. The elytra have parallel borders, narrowed at the back part, with well-developed sharp punctuation at the base, covered by ochre and gray hairs forming a small-speckled pattern. The length of front legs is almost equal to the length of the other legs. The mid tibia has a brush of golden-brown bristles on the external distal part. The underside of the body is covered with gray hairs that lay flat. The female antennae appear striped because the base of each segment has rings of gray hairs). They are equal to or slightly longer than the body. Male antennae are black and 1.5 times longer than the body. The weight of a young adults ranges between 125-246 mg (Florov 1951, Plavilshchikov 1958, Rozhkov et al. 1966, Cherepanov 1983).

Testing Methods for Identification:    Identification of Cerambycidae to species must be done from adults. Adults suspected of being Monochamus impluviatus should be examined by a taxonomist with expertise in the family Cerambycidae.

Monochamus beetles are strong fliers. However, the normal flying distance for Monochamus spp. adults in forests is fairly short.

Larvae can survive in lumber cut from infested logs and develop into adults. Therefore, unprocessed logs, lumber, wooden crating, pallets and dunnage used in international trade are a potential sources of introduction. Records from USDA APHIS indicate that between 1985 and 1998, insects believed to be Monochamus spp. were intercepted on over 250 occasions in U.S. Ports of Entry.

Averenski, A. I. 1971. Longhorn beetles (Coleoptera, Cerambycidae) of South-Western Yakutia. In: Insects and nematodes pests in Yakutia. Yakutsk:Yakutsk Book Editing Office, pp. 7-9 (in Russian).
Browne, F.G. 1968. Pests and diseases of forest plantation trees. Oxford: Clarendon Press, 1330 pp.
Cherepanov, A. I. 1983. Longhorn beetles of Northern Asia (Lamiinae: Dorcadionini-Apomecynini). Novosibirsk: Nauka, 267 pp. (in Russian).
Florov, D. N. 1951. Pests of Siberian pine. Irkutsk: Regional State Editing Office, 123 pp. (in Russian).
Issaev, A. S. 1966. Borer pests of Larix dahurica. Moscow: Nauka, 148 pp. (in Russian).
Issaev, A. S.; Tarassova, D.A. 1965. Borer pests of pine in Central Amur river basin. In: Study of Siberian Forests Protection. Moscow: Nauka, pp. 5-19 (in Russian).
Ivliev, L. A.; Kononov, D.G. 1966. Longhorn beetles (Coleoptera, Cerambycidae) of Magadan region. In: Entomofauna of forests of Kouril islands, Kamchatka and Magadan region. Moscow-Leningrad: Nauka, pp. 112-124 (in Russian).
Kondakov, Yu. P.; Knor, I. B.; Petrenko, E. S. 1979. Ecological and economical groups of forest insects of Baikal Basin. In: Fauna of Forests of Baikal Lake Basin. Novossibirsk:Nauka (Siberian Department), pp. 44-77 (in Russian).
Krivosheina, N. P.; Kompantsev, A. V. 1987. Longhorn beetles of Monochamus GUER. family in forests of taiga zone. In: Associations of xylophilous insects in conditions of over humidity. Moscow: Nauka, pp. 118-135 (in Russian).
Kulinich, O. A.; Orlinskii, P. D. 1998. Distribution of conifer beetles (Scolytidae, Curculionidae, Cerambycidae) and wood nematodes (Bursaphelenchus spp.) in European and Asian Russia. EPPO Bulletin 28: 39-52.
Lindeman, G. V. 1979. Xylophagous insects in forests of Eastern Khangai. In: Insects of Mongolia. V. 6, Leningrad: Nauka, pp. 7-17 (in Russian).
Mamaev, B. M. 1985. Borer pests of forests of Siberia and the Far East. Moscow: Agropromizdat, 208 pp. (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).
Plavilshchikov, N. N. 1958. Monochamus impluviatus Motsch.-Siberian speckled sawyer. Fauna of the USSR; Coleoptera. V. XXIII, Part 1; Long horn beetles, Part 3; Sub-family Lamiinae, Part 1, pp. 526-528 (in Russian).
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:
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CREATION DATE:        05/07/02