Dendrolimus sibiricus

 
IDENTITY
Name:   Dendrolimus sibiricus
Pest Authorities:  Tschetwerikov
Taxonomic Position:  Insecta: Lepidoptera: Lasiocampidae
Sub-specific Taxon:  
Pest Type:   Insect
Common Name(s):
   Larch caterpillar (English translation of Chinese common name)
   Siberian coniferous silk moth (English)
   Siberian lasiocampid (English)
   Siberian lasiocampid (English)
   Siberian silk moth (English)
Synonym(s):
   Dendrolimus laricis Tschetverikov
   Dendrolimus superans sibiricusTschetverikov
 
RISK RATING SUMMARY
Numerical Score:  9
Relative Risk Rating:  Very High Risk
Uncertainty:   Uncertain
RISK RATING DETAILS
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: In its native range, this insect damages more than 20 species of trees in several genera including Pinus, Abies, Larix, Picea and Tsuga. These genera are also widely distributed in North America. This insect also has a wide climatic range and is considered the most important pest of coniferous forests in Russia (from the center of European Russia to the Far East), Kazakhstan, Northern China, Korea and Northern Mongolia.

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: Both males and females fly and can disperse over long distances either on their own or assisted by air currents. Larvae are also subject to wind dispersal. In Russia this insect is presently extending its range westward at the rate of between 12 and 50 km per year. Dendrolimus sibiricus has a high reproductive potential. Females lay an average of 200-300 eggs. Conifer forests have more or less continuous distributions in North America, especially in the boreal forests of Canada and the northern U.S. Populations could go undetected, especially in remote areas and eradication techniques would be logistically difficult and probably ineffective. This insect has a broad host range and could adapt to many North American conifers.

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.
Justification: Dendrolimus sibiricus is able to attack and kill healthy trees over large areas. Direct control programs are undertaken over extensive areas against this insect in its native range to protect forests and prevent significant economic losses.

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.
  • Organism is expected to have indirect impacts on species listed by Federal, Provincial, or State agencies as endangered, threatened, or candidate. This may include disruption of sensitive or critical habitat.
  • Introduction of the organism would likely result in control/eradication programs that may have potential adverse environmental affects.
Justification: Tree killing by outbreaks of Dendrolimus sibiricus or by seconday bark beetles and woodborers in trees weakened by defoliation can result in significant ecological changes. Large-scale control programs needed to reduce damage and slow spread would have adverse effects on non-target organisms.

 
HOSTS
Dendrolimus sibiricus can damage more than 20 species of Abies, Pinus, Larix, Picea and Tsuga. It can develop on practically all coniferous species within its natural range including Abies sibirica, Abies nephrolepis (= Abies gracilis), Pinus sibirica, Pinus koraiensis, Larix gmelinii (= Larix dahurica), Larix sibirica (=Larix sukaczevii), Picea jezoensis and Picea obovata.

 
GEOGRAPHICAL DISTRIBUTION
Asia:
     Russia (practically all Asian Russia except extreme north), Kazakhstan, China (north), Korea Democratic People's Republic, Korea Republic, Mongolia (north).
Europe:
      Russia (central and northern European Russia). The Siberian silk moth appears to have originated in Siberia but has been spreading westwards at a rate that has been variously estimated from 12 km to 40 - 50 km per year. In 1955, Okunev (1955) reported that it had reached longitude 37° or 38° in European Russia (including the White Sea coast), but a later opinion place the most western point much further to the east, at longitude 52° (Rozhkov, 1963). Some of the uncertainty in the past about the precise distribution of Dendrolimus sibiricus may derive from confusion with other species, especially D. pini (Gninenko, personal communication).
 
BIOLOGY
The genus Dendrolimus consists of about 30 species of conifer feeding Lepidoptera, several of which periodically reach epidemic levels and can cause severe defoliation over large areas. All are primarily Asian species except D. pini, which is also found in western Europe. This genus is not represented in North America.

The taxonomy and synonymy of the genus Dendrolimus is complex. Many Russian scientists recognize the species Dendrolimus superans (the coniferous moth) with two subspecies: Dendrolimus superans sibiricus Tschetverikov (Siberian moth) and Dendrolimus superans albolineatus Matsumura (Sakhalin moth) (Rozhkov 1963, Epova and Pleshanov 1995). But, according to international opinion, Dendrolimus superans sibiricus is synonymous with Dendrolimus sibiricus (Siberian moth), and Dendrolimus superans albolineatus with Dendrolimus superans.

The spring flight of the Siberian silk moth usually occurs in the middle of July at the center of its natural range. Immediately after mating, females lay eggs on the needles, mainly in the lower part of the crowns. During outbreak years, eggs are laid throughout the tree and on the surrounding ground. An egg mass may contain up to 200 eggs. One female usually lays a total of 200-300 eggs, but some individuals can lay up to 800 eggs (Rozhkov 1963, Vorontsov 1995).

The egg stage is present in the field for about 13-15 days (with a maximum of 20-22). First instar larvae eat the edges of needles and molt in 9-12 days. Second instar larvae cause even more damage to the needles and develop for 3-4 weeks before molting. Third instar larvae migrate to the soil in September and overwinter under the moss.

At the end of April the following spring, the larvae return to the crowns and feed on remaining needles and the bark of young shoots and cones. They molt after one month and again at the end of July or early August. In autumn, the larvae migrate to the soil and overwinter for a second time.

In May and June of the next year, the larvae feed intensively. During this period, they eat about 95% of the food they need for their development and it is then that the major damage occurs. In total, larvae molt 5 to 7 times and have, correspondingly, 6 to 8 intars. In June, larvae construct cocoons. Pupation takes about one month.

The full life cycle usually takes two years. In the southern parts of its natural range, however, one generation can develop in a single year, whereas, in northern regions, the development of a generation sometimes requires three years (Rozhkov 1963, Galkin 1993, Vorontsov 1995).

Natural enemies of Siberian silk moth include several parasitoids and insect pathogens. Parasitoids include Telenomus gracilis, T. tetratomus (Hymenoptera: Scelionidae) and Trichogramma dendrolimi (Trichogramidae), which attack the eggs and Rhogas dendrolimi (Hymenoptera: Braconidae) and Ooencyrtus pinicolus (Hymenoptera: Encyrtidae), which attack the larvae and pupae. Insect pathogens include a bacterium, Bacillus dendrolimus, the fungus, Beauveria bassiana, and some viruses. These play an important role in the regulation of insect populations (Nikiforov 1970, Gorshkov 1973, Baranovskii et al. 1988, Yang and Gu 1995, Vorontsov 1995).

 
PEST SIGNIFICANCE
Economic Impact:    Siberian silk moth is the most important defoliator of conifers (Siberian pine, larch, fir and spruce) in Russia and Kazakhstan (Rozhkov 1963, Epova and Pleshanov 1995, Vorontsov 1995), and one of the most important defoliators of larch in China (Yang and Gu 1995). Outbreaks can occur over many thousands of hectares and lead to the death of entire forests. The evaluation made by Florov (1948) showed that during 90 years (1855-1945), the Siberian silk moth killed about 4 million hectares of Russian forests. According to Kolomiets (1958), during the 25-year period between 1932-1957, the Siberian silk moth damaged 7 million hectares of forests in Western Siberia and China alone, and caused the death of forests over half of this area. Similar data have been published by other scientists (e.g. Rozhkov 1963).

Outbreaks of the Siberian silk moth occur with a periodicity of 10 - 11 years (Rozhkov 1963, Epova and Pleshanov 1995, Vorontsov 1995) and are often preceded by two or three years of dry weather. Some scientists found that the cycle of these outbreaks coincide with the cycle of solar activity, and the maximum development of the outbreaks occurs in years of increasing number of sunspots (Galkin 1975, 1992). The defoliation usually lasts two or three years and many trees are unable to withstand such a long period of defoliation. Furthermore, the outbreaks of Siberian silk moth are also often followed by outbreaks of bark beetles and woodborers (Scolytidae, Cerambycidae and Buprestidae), particularly Ips typographus, I. subelongatus, Scolytus morawitzi (Scolytidae), Monochamus galloprovincialis, Xylotrechus altaicus (Cerambycidae), and Melanophila guttulata, (Buprestidae) (Pavlovskii and Shtakelberg 1955, Rozhkov 1963, Mamaev 1990, Epova and Pleshanov 1995, Vorontsov 1995). These insects are able to kill trees weakened by defoliation caused by Siberian silk moth.

Environmental Impact:   Defoliation by Siberian silk moth causes death of forests over large areas, either directly or by leaving the forest susceptible to subsequent attack by other forest pests, and/or by predisposing the forest to forest fires (Rozhkov 1963, Mamaev 1990, Epova and Pleshanov 1995, Vorontsov 1995 ). Natural regeneration of these areas is often difficult and takes much time. Moreover, widespread use of biological and/or chemical insecticides for control of outbreaks can have undesireable effects on non-target species.

Control:    Large-scale control programs, which consist of aerial applications of chemical and biological insecticides, (e.g. Bacillus thuringiensis) are conducted each year by the Federal Forest Service of Russia (Baranovskiiet al.1988, Maslov 1988, Epova and Pleshanov 1995, Vorontsov 1995) and other countries where this insect is an important pest.

 
DETECTION AND IDENTIFICATION
Symptoms:    Defoliation of pine, larch, fir or spruce is usually spectacular and occurs over large areas. The presence of caterpillars is easily detected.

Morphology:    The female adult has a wingspan of 60-80 mm. The male adults have a wingspan of 40-60 mm. The female body length averages 39 mm, and the male body length averages 31 mm. The color of the moths varies from light yellowish-brown or light gray to dark brown or almost black. Front wings are marked by two characteristic dark stripes. A white spot is located at the center of front wing.

The mature larvae are 55-70 mm long and the 2nd and 3rd segments are marked with blue-black stripes.

Testing Methods for Identification:    Both the larvae and adults have sufficient characteristics to facilitate preliminary field identification. However, examination of adults by a taxonomist with expertise in the order Lepidoptera is required for positive identification.

 
MEANS OF MOVEMENT AND DISPERSAL
Siberian silk moth can spread by flights of the adult moths (up to 100 km. per year) (Rozhkov 1963). All life stages of this insect could be transported on plant materials or wood products via international trade.

 
BIBLIOGRAPHY
Baranovskii, V. I.; Remorov, V. V.; Lamikhov, K. L. 1988. Ecological aspects of using micro-organisms against Dendrolimus sibiricus. Lesnoe Khozyaistvo 8: 54-55 (in Russian).
Epova, V. I.; Pleshanov, A. S. 1995. The forest regions injured by phyllophagous insects in the Asian Russia. Novosibirsk: Nauka, Siberian Publishing Firm RAS, 147 pp. (in Russian).
Florov, D. N. 1948. Pest of Siberian forests (Siberian silk moth). Irkutsk: OGIZ, 23 pp. (in Russian).
Galkin, G. I. 1975. Outbreaks of Dendrolimus sibiricus and solar activity. Lesnoe Khozyaistvo 8: 83-85 (in Russian).
Galkin, G. I. 1992. Periodicity of the mass breeding of pests. Zashchita Rastenii 12: 37-39. (in Russian).
Galkin, G. I. 1995. The forestry importance of insect pests in Central Evenkia. Lesnoe Khozyaistvo 6: 47-49. (in Russian).
Galkin, G. I. 1990. Reduction of the vitality of larch stands as a result of damage by Dendrolimus sibiricus. Lesnoe Khozyaistvo 1: 57-59 (in Russian).
Galkin, G. I. 1993. Biology of the Siberian moth (Dendrolimus superans sibiricus) in Evenkia. Zoologicheskii Zhurnal 72(6): 142-146 (in Russian).
Gorshkov, N. V. 1973. Role of egg parasites in regulating the population of Dendrolimus sibiricus. Lesnoe Khozyaistvo 4: 75-77 (in Russian).
Issaev, A. S.; Kondakov, Y. P.; Kisselev, V. V. 1995. Spatial structure of Dendrolimus sibiricus populations between outbreaks. Lessovedenie 6: 3-12 (in Russian).
Kolomiets, N. G. 1958. Phytocenological characteristics of outbreaks of Siberian silk moth in Western Siberia. In: First Inter-Universities Conference on Forest Protection. Abstracts of Presentations, Moscow, pp. 37-38 (in Russian).
Koltunov, E. V.; Fedorenko, S. I.; Okhlupin, O. V. 1997. Dendrolimus sibiricus in the spruce-fir forests of the plains east of the Urals. Lesnoe Khozyaistvo 2: 51-52 (in Russian).
Mamaev, Y. B. 1990. Foci of stem pests in larch forests of the Tuva ASSR damaged by Dendrolimus sibiricus. Izvestiya vysshikh uchebnykh zavedenii - Lesnoi Zhurnal. 2: 16-19 (in Russian).
Maslov, A. D. 1988. Guide on forest protection against pests and diseases. Moscow: Agropromizdat, 414 p. (in Russian).
Nikiforov, G. M. 1970. The characteristics of a massive outbreak of the Siberian lasiocampid [Dendrolimus sibiricus]. Zashchita Rastenii 9: 38-39 (in Russian).
Okunev, P. P. 1955. Geographical distribution and zones of injuriousness of Siberian silk moth. In: Geographical Problems in Forestry, Moscow - Leningrad: Edition of Academy of Scienses of the USSR, V. 5, pp. 32-48 (in Russian).
Pavlovskii, E. N.; Shtakelberg, A. A. and others. 1955. Forest pests guide, Volume 1. Moscow - Leningrad: Edition of Academy of Sciences of the USSR. 421 p. (in Russian).
Rozhkov, A. S. 1963. Siberian silk moth. Moscow: Edition of Academy of Sciences of the USSR, 176 pp. (in Russian).
Vorontsov, A. I. 1995. Forest entomology: Manual for universities, 5th edition. Moscow: Ecologia, 352 pp. (in Russian).
Yang-ZhongQi; Gu-YaQin. 1995. Egg parasitic wasps of the larch caterpillar in Daxinganling mountains with a description of a new species. Scientia Silvae Sinicae 31(3): 223-231 (in Chinese).
 
AUTHOR(s)
Name(s):
Andrei Dorian Orlinski
 
 
Name and Address of the First Author:
Andrei Dorian Orlinski
Europe
EPPO
1, rue Le Nôtre
Paris,
France 75016
 
CREATION DATE:        11/29/00
MODIFICATION DATE:        11/29/00

    
Selected images from Forestry Images (www.forestryimages.org)
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1241016

Larva(e)
in Mongolia
Photo by John H. Ghent,
USDA Forest Service


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1241015

Egg(s)
in Mongolia
Photo by John H. Ghent,
USDA Forest Service