Why is the Siberian silkworm dangerous? Siberian silkworm - one of the most dangerous insect pests

06.03.2020

Siberian silkworm
and the fate of the fir taiga

D.L. Grodnitsky

Dmitry Lvovich Grodnitsky, Doctor of Biological Sciences,
head cafe natural disciplines Institute of advanced training of educators (Krasnoyarsk).

Who has not heard about the gluttony of locusts, which, during mass reproduction, unites in multi-million flocks, flies hundreds of kilometers in search of food and destroys crops of grain and cotton, orchards and vineyards in a matter of hours, and eats not only leaves, but also branches, and even bark from the trees? Many times, locusts doomed hundreds of thousands of people to starvation. Those who were lucky enough to survive the invasion erected monuments in honor of their salvation. However, the locust rages mainly in the tropics and subtropics, while for the Siberian forests, the mass reproduction of the less known, but no less voracious insect, the Siberian silkworm, becomes a real disaster ( Dendrolimus sibiricus). It was first described by S.S. Chetverikov more than a hundred years ago. Nowadays, the silkworm has ceased to be exclusively Siberian: the western border of its range has long passed the Urals and continues to slowly move through the European part of Russia.

The adult Siberian silkworm is a large butterfly up to 10 cm (usually four to seven) in wingspan; males are smaller than females. Butterflies do not feed (they do not even have a proboscis), but the caterpillars have an excellent appetite. They eat the crowns of all species of coniferous trees growing in Siberia, but most of all they prefer the needles of larch, fir and cedar, a little less - spruce, and even less pine. At the same time, the caterpillars behave rather strangely: for one to two weeks they actively feed and gain weight, after which an incomprehensible period of rest (diapause) occurs, when they hardly eat. By the way, caterpillars of another pest (also quite large) - gypsy moth ( Lymantria dispar) - feed continuously and completely complete development within a month and a half, but the life cycle of the Siberian silkworm usually stretches for two years. The biological meaning of a short-term diapause in summer, when everything seems to be favorable for the growth and development of the larva, is still unclear.

Ecological catastrophy?

The Siberian silkworm is a common inhabitant of forest ecosystems; in a healthy forest, it is constantly found in small quantities (one or two caterpillars per dozen trees) and, accordingly, there is little harm from it. Another thing is when there is a mass reproduction of an insect or, as this state of the population is also called, an outbreak of numbers. The reasons for this can be very different. For example, drought: after two or three warm dry seasons, instead of the usual two years, caterpillars manage to develop in a year. As a result, butterflies born in the past and the year before lay eggs this year. The population density doubles, and natural enemies - insects-entomophagous, usually destroying almost all individuals of the silkworm - manage to hit only half of its ovipositors and caterpillars, while the rest develop unhindered, pupate, turn into butterflies and give offspring. In addition, the increase in the number of silkworms may be associated with spring ground fires. The fact is that the caterpillars spend the winter under the forest floor, from where they emerge with the first thawed patches and rush into the crowns of trees. The worst enemy of the silkworm, the microscopic egg-eater telenomus, also hibernates in the litter ( Telenomus). Its females attach themselves to the body of a silkworm (up to 50 telenomus on one butterfly), travel considerable distances to the place of laying eggs, and then strike them. Since the silkworm lays eggs towards the middle of summer, egg-eaters are in no hurry to leave the litter. Even a light fire that has passed through the dried grass in early spring destroys b about most of the population of these insects, which contributes to the emergence of centers of mass reproduction of the silkworm. After two or three years, the caterpillars completely destroy the needles even on the largest tree and then crawl to neighboring areas in search of food.

In Siberia, such centers of mass reproduction (silkworms) are formed in forests of two types: pure (single-species) larch forests (in Yakutia, Khakassia and Tuva) and in dark coniferous taiga (in Altai, in Novosibirsk, Kemerovo, Tomsk, Irkutsk regions and Krasnoyarsk Territory). The effects of outbreaks in these two types of forests are quite different, as different types of trees tolerate silkworm infestations in different ways.

Larch within a month after damage is able to form secondary (compensatory) needles, which are longer, lighter than the original and have less photosynthetic activity. Nevertheless, this needle is enough to help the tree survive the loss of the crown. As a rule, larch suffers one- and two-time damage by caterpillars. The exceptions are areas with unfavorable growing conditions: arid, like Tuva, or permafrost, like Evenkia.

In the dark coniferous Siberian taiga, if there is larch, then in small quantities, the silkworm does not eat the leaves of aspen and birch, so the fate of the taiga depends on the stability of Siberian fir (60-100% of the forest stand), spruce and cedar. Fir and spruce are not capable of forming secondary needles and dry out after a single overeating. Cedar, on the other hand, with the same trunk diameter, has twice the biomass of needles than that of fir. Accordingly, in order to destroy the crown of a cedar, caterpillars need twice as much time or twice as many. However, this feature of the cedar does not change the situation.

It is believed that dark coniferous forests after death will sooner or later recover naturally due to succession - the successive replacement of some biocenoses by others (grass community - deciduous and, finally, coniferous forest). This is true, but not in the case when the death of the taiga is caused by the mass reproduction of the silkworm. Unfortunately, not only the townsfolk, who see no reason for concern, are mistaken, but also forestry workers.

In reality, after the outbreak of the silkworm population, the following happens. All coniferous trees, including the younger generation, die, the remains of crowns crumble. The amount of light reaching the ground is doubled. As a result, forest grasses begin to grow, which were previously in a depressed state due to shading, and after a year or two the soil is hidden under a dense grass cover. Reed grass predominates among herbs ( Calamagrostis) - a cereal that causes the rapid formation of sod (a surface layer of soil penetrated by densely intertwined roots and underground shoots). A dead stand does not take moisture from the soil, as a result of which a swamp gradually forms under the silkworms. The trunks of dead trees rot and begin to fall five to seven years after the outbreak. Within 10 years, the area of mass reproduction of the silkworm turns into a dump of rotting wood. Such areas are impassable not only for humans, but also for animals.

Change of vegetation in the taiga ecosystem, where the needles were destroyed by the Siberian silkworm.
The numbers indicate the approximate number of years required to complete each stage of succession.

It takes 10-20 years for the microorganisms to destroy the remnants of wood and gradually make room for young birch trees. However, in most cases, the growth of a new generation of trees is hindered by fires. It is known that silkworms burn several times, so as long as combustible residues remain in the former hearth, trees do not grow there. In fact, during the first three decades, silkworms do not produce wood. Only after the disappearance of the fire danger, the growth of birch begins.

Even 50 years after the mass reproduction of the silkworm, the former taiga area is covered with dense thickets of birch with a trunk diameter of 2-8 cm. about 20 cm). How long does it take for the original taiga vegetation to recover in such an area?

To begin with, soil moisture should decrease, since the main species that determines the appearance of dark coniferous forests on the plain is fir, which does not tolerate waterlogging. It can be expected that within a few decades the growing birch forest will drain the soil and it will become suitable for fir seedlings.

But where do the seeds come from in the silkworm? A certain amount of pine nuts can be brought by birds, but their role cannot be overestimated. Spruce seeds, sown from cones in winter, can be brought by the wind along the crust. However, the most important thing is the natural sowing of fir - the main forest-forming species. Fir cones disintegrate in autumn. At the same time, the seeds do not fly far: special measurements show that the range of their distribution does not exceed 100 m, and the bulk settles 50-60 m from the mother trees. It turns out that silkworms have a chance to be sown sooner or later only if they have a small area.

So it is, but coniferous seedlings, even if they were able to take root in the sod (which is unlikely), there is no way to compete with reed grass, which grows incomparably faster. This circumstance fully corresponds to the established fact: on the border of the silkworm, all young coniferous trees are concentrated in a hundred-meter strip along the forest edge, which annually produces seeds of fir, spruce and cedar. At the same time, only cedar and spruce are represented in the undergrowth; fir is present singly. Moreover, the density of undergrowth is only 200-300 specimens per hectare, and for forest restoration, their number should be at least ten times higher.

So, contrary to popular belief, the natural restoration of dark coniferous forests after their destruction by the silkworm is unlikely: rare trees appear only in close proximity to a healthy forest. Let's add to this that the area of 20-30 thousand hectares is not the limit for the silkworm. It is clear that the probability of getting a sufficient number of seeds into the silkworm is low, and the successful development of seedlings and the further growth of a new generation of conifers is practically impossible. As a result, after repeated fires, growth and subsequent natural thinning of birch thickets, approximately in the sixth or eighth decade after the mass reproduction of the silkworm, a birch sparse forest appears on the site of the dark coniferous taiga.

There is another misconception: silkworm outbreaks occur at intervals of 11-13 years. To doubt this, one need only look at a simple chronicle of recent events. During the decade from 1992 to 2001, silkworm foci were noted in Novosibirsk oblast. (1995-1999), in Tomsk (1995-1996 and 2000-2001), in Altai and Tuva (1992-2001), in the Kemerovo region. (1998-2000), in Khakassia (1999-2000), in the Krasnoyarsk region (1992-1997 and 2000-2001), in the Irkutsk region. (1995-2001), in Buryatia (1992 and 1997-2001), in the Chita region. (1999-2001), in Yakutia (2000-2001). At the same time, foci with a total area of more than 50 thousand hectares were found in Altai, Tuva, Irkutsk region. and others. Only in the Krasnoyarsk Territory for three years (1992-1995) silkworms killed fir forests on an area of 260 thousand hectares; in some areas, almost a fifth of all dark coniferous forests disappeared. I note that this is information from official forestry statistics, reporting only on the foci found, but not on all active foci.

The conclusion is obvious: in Siberia, the silkworm annually damages forests on an average area of about 100 thousand hectares, a significant part of which turns into vast treeless spaces; accordingly, the activity of the silkworm is difficult to characterize otherwise than as an ecological disaster.

Theory and practice

They say that preventing a disease is easier than curing it, and one cannot but agree with this. Outbreaks of phytophage numbers are an obvious pathology of the biocenosis, from which all organisms inhabiting it suffer. The pest itself is no exception: for many years after the mass reproduction of the silkworm, it is difficult to detect in the vicinity of the outbreaks.

To establish the beginning of mass reproduction, monitoring is carried out - a set of measures to monitor the number of pests. If the number has exceeded a certain threshold, then the treatment (usually from the air) of the emerging foci with chemical or bacterial insecticides is prescribed.

The theory is good, but the reality is more complicated. The forests of Siberia are difficult to access at best, so monitoring can only be carried out in relatively few areas. Even if an increase in numbers is noted in some of them, it is almost impossible to establish the true boundaries of the beginning outbreak. This is exactly what happened in the Krasnoyarsk Territory in 1990-1992, when the impending catastrophe was forestalled two years in advance and appropriate measures were taken. However, the ensuing mass reproduction led to the formation of foci in the territory of 250-120 km; it is technically impossible to cover such an area with aerial treatments, not to mention the cost of such activities. It is reasonable to assume that the centers of the Siberian silkworm will continue to form. What to do?

Funds from the Russian forestry arsenal are few. One of the methods actively discussed these days is the so-called “controlled burning”, a technology imported into Russian forestry practice, as always, from the USA, where burning is used quite often. However, even with American technology and organization, the fire is not always managed to be kept under control, and then much more burns than was planned. In Russia, under the existing circumstances, the fire has much more opportunity to escape into the surrounding forests. The consequences of burning dry forest stands on an area of several thousand hectares are quite obvious. Due to these circumstances, one can hardly expect that the burning of silkworms will take any significant place in domestic practice.

Atmospheric explosion of accumulation of underoxidized substances,
formed during combustion in conditions of lack of oxygen, -
one of the phenomena accompanying large forest fires.
Photo by V.I.Zabolotsky

It remains only to chop the silkworms; both economic and environmental considerations lead to this conclusion. Otherwise, the silkworm will rot and pose a constant fire hazard. Suffice it to say that the volume of dead wood in the already mentioned Krasnoyarsk silkworms amounted to about 50 million m 3 . What impact will the astronomical amount of decay and combustion products emitted into the atmosphere have on climate processes? What will be the geographic scope of this influence? The significance of this aspect of silkworm activity has yet to be assessed.

It is obvious that the Siberian silkworm poses a real threat to the very existence of the fir taiga on the plains of Western and Eastern Siberia. Consequently, the introduction of a specially protected area regime is required, at least for that part of the forests where Siberian fir dominates, if these forests are located in the zone of the harmful effect of Siberian silkworm populations.

An anthropogenic crisis?

It is assumed that outbreaks of the Siberian silkworm are a natural, evolutionarily determined phenomenon. Otherwise, one would have to believe that the ecosystem is capable of self-destruction: after all, the Siberian silkworm is not an alien species, not an invader, but an original taiga inhabitant, i.e. part of the ecosystem. But how, in this case, could the dark coniferous taiga of Siberia - a native forest formation - arise in the conditions of permanent large breeding centers of the silkworm? Another explanation looks more realistic: outbreaks of this insect arose relatively recently as a result of a disruption in the balanced functioning of taiga ecosystems, which could be caused by human agricultural and logging activities that began in Siberia less than four centuries ago. Fire farming led to the fragmentation of biocenoses and the formation of heated forest edges. The sudden lightening of the crown has a depressing effect on the fir and suppresses its protective reaction to insect damage. It is possible that the increase in temperature and the suppression of the immunity of the forage plant once accelerated the development of the Siberian silkworm and allowed it to elude the numerous natural enemies that regulate its numbers. As a result, the system went out of balance - human activity served as a trigger for a process that destroys the natural biocenosis.

This point of view is in good agreement with the fundamental idea of V.V. Zherikhin about the evolution of biological communities, developed on the basis of a deep comparative study of the change of fossil faunas. The development of life on Earth has repeatedly passed through periods of mass extinction of some and the emergence of other creatures. The change in the composition of the fauna occurred against the background (and because of) the ecological crisis caused by depression and the disappearance of dominants (edificators) - plants that determined the appearance and structure of ecosystems of the distant past. In place of extinct communities, new ones arose. In particular, all stable grass communities (steppes, prairies, pampas) historically formed on the site of succession series with forest climaxes due to the loss of the last stages, where trees dominated. The latter is understandable: in any series of community change, the most vulnerable stage is the initial one; if it were stable, there would be no succession at all. Therefore, if the final stages are regularly destroyed by some factor and the succession system returns to its original state, then there is a possibility of the ecological space being captured by other species that will not allow further changes in cenoses along the knurled path. “Other species” are not aliens, but inhabitants of local ecosystems, usually in a depressed state, but able to grow rapidly and hold the territory when suitable conditions occur. In the situation with the taiga and the Siberian silkworm, the role of the invader species is played by the reed grass.

The observed pattern is not identical to those known from paleoecology. Fossil forests have disappeared with the active participation of large leaf-eating mammals, while the dark coniferous taiga is being destroyed by insects. And yet, the fundamental scheme is repeated: the consumer of the first order transfers the forest ecosystem to the initial stage of succession, after which the position of the edificator in the plant community is occupied by one of the common, but not previously dominant species, which modifies the environment in such a way that the path to the former climax ecosystem is closed. .

If the noted similarity is not superficial, then the presented example illustrates the process of the anthropogenic biospheric crisis, which V.V. Zherikhin repeatedly spoke about - a radical restructuring of the entire biota caused by human activity. Of course, the crisis did not start now: outbreaks of locusts plagued people long before our era. But biocenotic crises do not occur overnight. Anomalous natural phenomena have been following the development of civilization for thousands of years, the established structure of the biosphere is being shaken slowly and little by little, but you still need to think about the consequences.

Literature

1. Kolomiets N.G. Siberian silkworm - a pest of the lowland taiga // Tr. according to the forest hoz-vu. Novosibirsk, 1957. Issue 3. pp.61-76.

2. Kuzmichev V.V., Cherkashin V.P., Korets M.A., Mikhailova I.A.// Forest science. 2001. No. 4. pp.8-14

3. Savchenko A.M. On the distance of scattering of seeds of Siberian fir in lowland forests // Tr. SibNIILP. 1966. Issue 14. S.3-5.

4. Kondakov Yu.P. Patterns of mass reproduction of the Siberian silkworm // Ecology of populations of forest animals in Siberia. Novosibirsk, 1974. S.206-265.

5. Official data of the Russian Center for Forest Protection.

6. Talman P.N. The influence of the environment and the human role that transforms it in connection with the reproduction of the Siberian silkworm // Tr. LTA. 1957. Issue 81. Part 3. pp.75-86.

7. Zherikhin V.V. Selected works on paleoecology and phylocenogenetics. M., 2003.

- a butterfly of large size with an inconspicuous color of the wings, the insect belongs to the family of cocoonworms. Females are larger than males: the wingspan is 6-8 cm, which is one and a half to two times the wingspan of males. The yellowish-brown or light gray color of the wings allows insects to skillfully disguise themselves on the bark of trees, and serves as protection.

Spreading

Widely distributed on the territory of Russia, the habitat is limited to the Ural, West Siberian, East Siberian and Far Eastern regions. It is on the territory of Siberia and the Far East that the Siberian silkworm has a quarantine value, as it is the worst pest of coniferous trees. Experts note that in recent years the population has been actively moving to the west of Russia.

The threat to conifers does not come from the butterfly itself, but from its caterpillars. Caterpillars of the Siberian silkworm hatched from eggs are easily acclimatized, hardy and very voracious.

Life cycle

An adult butterfly lays its eggs on the branches of coniferous trees, usually larch, fir and spruce. On average, each female lays up to 300 eggs per season, some sources indicate that the maximum number laid by one female is up to 800 eggs. The shape of the greenish-blue egg is round, about 2 mm in size. One clutch can contain from 10 to 100 eggs.

The brown or brown caterpillars that emerged from the eggs immediately begin to actively feed on the delicate needles of trees. On average, the length of insects is 5-7 cm. Moving from the bottom of the crown to the very top, voracious larvae leave behind only gnawed branches, which has a detrimental effect on the health of trees. After the work of the silkworm, weakened trees become the prey of the barbel and die completely.

In order to transform into a butterfly, the caterpillar needs to survive two winters, feeding vigorously during the spring and summer (from May to mid-August). Entomologists distinguish 6-8 ages of the caterpillar, during which it passes 5-7 molts. Caterpillars that survive the second wintering cause the greatest harm to trees, it is at this time that they absorb 95% of the needles necessary to complete the development cycle. In June, the larva pupates, and after three to four weeks, a Siberian silkworm butterfly emerges from a large gray cocoon (28–30 cm), capable of continuing reproduction.

natural enemies

Like other insects, the Siberian silkworm has its own natural enemies: ichneumons, tahini flies or aquatic flies, egg-eating ichneumons. Braconids and Trichogramma take a particularly active part in regulating the number of agricultural pests. Trichogramma lay their offspring (up to four eggs) directly into silkworm eggs. Tahini are also insect-eating insects, but they lay their eggs in the body of an adult insect, which leads to its gradual death.

In some countries, these natural enemies of the silkworm are artificially acclimatized specifically in order to control the population of the latter.

In addition to these insects, the cuckoo, woodpecker, nutcracker, tit and other insectivorous birds feed on caterpillars and adult insects of the Siberian silkworm. Affect the development of insects and fungal infections.

pest danger

The danger of the species lies in the fact that the insect can increase the population several hundred times after passing a two-year cycle of development. In Siberia and the Far East, millions of hectares of healthy coniferous forests have died due to the harmful activity of the insect. Even natural enemies cannot cope with its invasion.

Gnawed needles cannot lead to the death of a healthy and strong tree, but it seriously weakens it, making it easy prey for wood pests. Bark beetles and barbels choose weak trees and use them to lay offspring in the subcrustal layer, after which the beetle larvae eat the tree from the inside. So the insects that have taken over the baton finally destroy the forest, turning it into dead wood, which is not suitable for serious construction work. It will take at least a hundred years to renew the forest in the ruined areas.

In order for the problem with the Siberian silkworm not to grow to global proportions, it is necessary to fight against a dangerous pest.

Spread prevention

Measures to combat the Siberian silkworm can be different: some are aimed at suppressing widespread distribution, others lead to a decrease in the population. The Rosselkhoznadzor recommended introducing strict phytosanitary control rules for timber exported from quarantine areas.

Phytosanitary restrictions include the following measures:

Disinfection and debarking of conifers before their transportation;
An accompanying certificate confirming the handling is required for the cargo.

These measures should help prevent the expansion of pests into uninfected regions.

Fighting the Siberian silkworm

Mechanical methods of destruction (collection of caterpillars and pupae, removal of infected needles) of the pest turn out to be of little effectiveness, since the pest centers are usually located in the remote taiga. Aerial photography or a careful visual inspection of the area will help identify dangerous zones. The territory with bare coniferous trees is marked on the map and, if the area is large, the area is disinfested.

To destroy the Siberian silkworm in heavily infested areas, it is necessary to resort to insecticides. Chemical treatment of conifers leads to mass death of caterpillars and butterflies. For this purpose, an insecticide is sprayed from the aircraft on the infected area.

When performing disinfestation, one should take into account the biology of the species and perform it twice a year: in the spring to destroy the overwintered caterpillars, at the end of summer to destroy the young ones preparing for wintering.

There are biological and chemical insecticides against the pest. Lepidocide can be distinguished from biological agents, which is successfully used to control caterpillars of harmful insects in parks and squares, in agriculture and forestry. The protein toxin contained in lepidocide causes paralysis of the gastrointestinal tract in caterpillars, they stop feeling hungry and die of exhaustion. The drug also affects adults: butterflies do not tolerate the smell of this drug, so their years decrease, and after it the number of eggs laid decreases.

Siberian silkworm - a thunderstorm of coniferous forest

To cope with the worst pest of conifers is possible only with the help of carefully organized detailed supervision and the fulfillment of all sanitization requirements. The fact that it is quite difficult to achieve real results in the destruction of insects of this species is evidenced by the dead forests of Siberia and the Far East.

Territories requiring special attention of supervisory organizations:

Areas that have experienced drought;
Fire-damaged area.

The experience of past years shows that it was in such regions, weakened by fires or climatic reasons, that the growth of the silkworm population began, often developing into huge foci of infection.

The coniferous forest is in serious danger, its future is in jeopardy if effective measures are not taken in a short time to combat the worst coniferous pest- Siberian silkworm (Dendrolimus superans). More and more of it began to be found in the coniferous forests of Russia. How dangerous is the Siberian silkworm, and what are the devastating consequences of its invasion for the prosperous existence of coniferous forests?

The Siberian silkworm butterfly is at first glance inconspicuous and seemingly absolutely safe. But this is far from true. These pests increasingly began to fall into special traps, and scientists sounded the alarm: the population of this pest is growing rapidly. In fact, a ten centimeter insect is not so dangerous, especially for coniferous forests, and its caterpillars hatched from eggs cause harm to forest plantations. They are able to quickly acclimatize, are quite hardy, and have excellent appetite.

An adult individual of the Siberian silkworm lays its eggs on the branches of coniferous trees. Hatching, the larva immediately begins to eat, moving from the lower crown to the very top, leaving behind only the merged branches. In October, the larva of the Siberian silkworm leaves for wintering, and in the spring of the next year, the larva of the third age also continues to feed throughout the warm season. Caterpillars of the Siberian silkworm eat almost all coniferous trees. After the fifth instar, the more voracious larva again leaves for wintering, after which a butterfly appears, which actively begins to lay eggs. In total, a female can lay about 800 eggs per season.

The Siberian silkworm is dangerous because it can cause mass breeding outbreaks, which will ultimately lead to the global death of millions of hectares of coniferous forests. This is exactly what happened in the Far East and Siberia. Coniferous forest in these areas simply amazes with its destruction and mass death. In these places, after the global growth in the popularity of the Siberian silkworm, all coniferous forest plantations, including the growing seedlings of coniferous pines and fir trees, died. The rest of the crowns crumbled. Scientists say that it will take about a hundred years for a coniferous forest to grow in its original place again.

To avoid the spread of the Siberian silkworm, Rosselkhoznadzor experts recommend introducing a number of phytosanitary restrictions: when exporting conifers, they must be debarked or disinfected in order to prevent the spread of the Siberian silkworm further through the coniferous forests of Russia. There is now increased attention to the export and import of coniferous wood: without an appropriate accompanying certificate, such a cargo may be illegal.

If you find a Siberian silkworm on the coniferous trees of your site, you must immediately organize measures to combat this pest. The natural enemies of the pine silkworm are the cuckoo, the rider insect and fungal infections.

In case of mass reproduction, coniferous trees should be treated with insecticides. The most effective biological drug at the present time is lepidocide.

And for the prevention of the Siberian silkworm, it is necessary to regularly inspect the trees for the presence of pests and carry out preventive treatment with insecticides.

Siberian silkworm

cedar silkworm (Dendrolimus sibiricus), a butterfly of the cocoonworm family, a dangerous pest of coniferous forests. Wingspan up to 90 mm, gray color. Distributed S. sh. from the shores of the Pacific Ocean in the east to the Southern Urals in the west and from Yakutia in the north to northern China in the south. It damages larch, fir, cedar, rarely spruce, and pine. The first butterflies appear at the end of June, the mass flight begins, as a rule, in mid-July and ends in the 1st half of August. N. sh. has a two-year or one-year generation. With a two-year generation, the number of caterpillar ages is 7-8, with a one-year generation - 5-6. Most of the caterpillars overwinter in the forest litter at the 3rd instar (in larch plantations more often at the 2nd instar). After the snow cover melts, they feed on needles, eating it entirely. Sometimes kidneys and even young cones are damaged. Eating needles is one of the reasons for the mass reproduction of stem pests (especially barbels), which damage plantations and lead to their death. Regulates the number of S. sh. its common natural enemy is the telenomus rider. Mass death of caterpillars N. sh. usually occurs as a result of epizootics caused by bacteria.

Control measures: the most effective spraying of foci of S. sh. during the period of development of caterpillars of younger ages with insecticides from aircraft. See also Art. Forest pests.

Lit.: Forest entomology, M., 1965.

N. N. Khromtsov.

Great Soviet Encyclopedia. - M.: Soviet Encyclopedia. 1969-1978 .

See what the "Siberian silkworm" is in other dictionaries:

Butterfly of the cocoonworm family; pest of coniferous tree species in Siberia, the Far East. Wings are grey. It feeds (caterpillars) on needles, buds, young cones ... Big Encyclopedic Dictionary

SIBERIAN SILKMOTH, a butterfly of the cocoonworm family; pest of coniferous tree species in Siberia, the Far East. Wings are grey. It feeds (caterpillars) on needles, buds, young cones ... encyclopedic Dictionary

SILKMOTH, a, husband. 1. Butterfly, caterpillar to a swarm weaves cocoons, going to the manufacture of silk (in 1 meaning). Mulberry sh. 2. Butterfly, caterpillar to the swarm is a pest of the forest. Siberian sh. Pine sh. Explanatory dictionary of Ozhegov. S.I. Ozhegov, N.Yu. Shvedova… … Explanatory dictionary of Ozhegov

Cedar silkworm (Dendrolimus sibiricus), a butterfly of the fam. cocoonworms. Wingspan up to 90 mm. Butterflies and caterpillars are similar to those of the pine cocoon moth. In Siberia, in the Far East, in the North. Mongolia, Sev. China, Korea, Japan. Mass flight in the 2nd ... Biological encyclopedic dictionary

BUT; m. 1. Butterfly, the caterpillar of which weaves cocoons, which are used to make silk (1 sign). Mulberry sh. 2. Butterfly, the caterpillar of which is a dangerous pest of tree plantations. Unpaired sh. Kedrovy sh. Siberian sh … encyclopedic Dictionary

silkworm- a; m. 1) a butterfly, the caterpillar of which weaves cocoons that are used to make silk 1) Silkworm / d. 2) Butterfly, the caterpillar of which is a dangerous pest of tree plantations. Gypsy moth/d. Cedar silkworm/d. Siberian silkworm / d ... Dictionary of many expressions

Svetlana Lapshina

Unexpectedly, almost all of Siberia this year was covered by a silkworm. The cedar forests suffered in the Kemerovo region (pests were registered on an area of about 12 hectares), in Irkutsk (about 50 thousand hectares), in the Krasnoyarsk Territory (about 1 million hectares).

- It was the youngest cedar. The average age of trees is 100-120 years, - Alexander Boltovsky, a local forester of the Bogashevskoye forestry, sighs, pointing towards the field. - The silkworm caterpillars ate this tree completely. In 32 years of work, this is the first time I see this.

Instead of a chic green crown, there are only bare branches - not a single needle on the tree. And there are dozens of such cedars ...

caterpillars attack

The Siberian silkworm destroyed two areas of plantings in the Luchanovsky settlement cedar forest (total area of almost 18 hectares) in three weeks of August. Local boys, climbing cedars for cones, told the forester: “Some worms are crawling upstairs.” But the experienced Boltovsky was already in the know.

- I walked around these foci ten times, calculated the area affected by the silkworm. The most important thing is to prevent the pest from spreading next year. In the spring, it is necessary to carry out the processing of these territories, and especially those areas that are adjacent to healthy plantations, explains Alexander Boltovsky.

There are about 5 thousand hectares of cedar forests in the Bogashevskoye forestry. Problems have arisen so far only in the vicinity of the village of Luchanovo.

Now the pest has left for the winter. We easily found silkworm caterpillars in the forest floor.

“There are so many of them,” Alexander Boltovsky demonstrates a harmful crop in his palm. - It seems that the caterpillars are dead? Nothing like this. Now they are in a state of suspended animation. And here is the cocoon. An adult individual of the Siberian silkworm will come out of it.

There is a chance the trees will survive. Because overeating was a single and in the autumn period. And the buds from which the needles grow are still alive.

Silkworm gave heat

The Siberian silkworm is a habitual inhabitant of our forests. With a low number, it does not pose a danger. However, favorable weather conditions for it - last year's warm winter and a long hot summer - provoked an uncontrolled population growth. As a result, in the Tomsk region, at the same time, centers of destruction of cedars by it broke out in the Bakcharsky, Verkhneketsky, Pervomaisky, Tomsk, Parabelsky, Kolpashevsky, Chainsky, Molchanovsky and Kozhevnikovsky districts.

Siberian silkworm outbreaks most often occur after two to three dry growing seasons. In such years, the most viable and prolific individuals appear, characterized by particular voracity.

- The territory affected by the pest is at least 424 thousand hectares. None of the experts expected such a rapid development of events, - explains Anton Balaburkin, chief specialist of the department for the protection and protection of the forest fund of the regional forestry department.

But this is not yet the final figure. Surveys in the region will last until the end of December. They are conducted by forest rangers and forest pathologists from the Forest Protection Center. The main task is to find out the boundaries of the outbreak and the number of the pest. Now experts are planning to examine the forest in the Teguldet region.

“It is very difficult but necessary work. It makes it possible to see the whole picture as a whole, - continues Anton Balaburkin.

Experts determine the number of Siberian silkworms by rounding several trees. They count the number of caterpillars that have fallen and, based on this data, draw conclusions about the threat of overeating. This indicator is necessary for planning actions to eliminate the centers of defeat of cedars for the next year. If the threat of overeating is 50% or more, special measures must be prescribed. When the silkworm caterpillar stops feeding and goes into the litter, forest pathologists excavate.

- A thousand caterpillars on a tree - this is not the limit. In some areas of the Bazoisky cedar forest of the Kozhevnikovsky district, their number on cedars reached two thousand. And six hundred caterpillars are enough for one hundred percent overeating, - comments Anton Balaburkin.

give to nuts

Almost 450 million rubles are needed to save the cedar forests. It is planned to allocate about 50 million from the regional budget for the next year to fight the Siberian silkworm. Therefore, the regional authorities turned to the Federation for support: Governor Sergei Zhvachkin wrote a letter to Rosleskhoz.

– It is impossible to write off the social significance of the cedar forests. Most of them are suburban, that is, they are located near settlements. And for many local residents, harvesting pine nuts is the main source of income, - Anton Balaburkin emphasized.

The ideal option is to treat the entire affected area. The optimal time for such work is the first decade of May. At this time, the caterpillars emerge from the litter, rise into the crown and begin to feed actively. And at this moment it is necessary to strike from the air - to spray with the help of air transport special means.

The Siberian silkworm is poisoned with the biological preparation Lepidocid. It is harmless to humans and animals, including bees.

“At the moment we are trying to obtain federal approval for the use of chemical control agents. Biological preparations are effective, but they have a very serious limitation - the temperature of application, - notes Anton Balaburkin. – Lepidocide operates at an average daily temperature of 18 degrees and above, and in early May it will be at most plus 10.

The problem is that all Russian chemicals have expired certification periods - they need to be extended. And this also takes time. In the Soviet years, there were more than 20 different means allowed for use. Tomichi appealed to the government with a request to use at least some of them.

The amount of work to be done is very large. But success will be achieved only if everything works out: federal money will come to the region, competitive procedures will be successfully completed ... The invaluable property of the region is at stake - His Majesty the Siberian cedar.

The caterpillar of the Siberian silkworm has six instars. The main nutrition occurs from the third age. For the third - fourth, the caterpillar eats at least 30% of the crown of the tree, for the fifth - sixth - everything else. In the Tomsk region there are areas where overeating is 100%.

In our region, there was an outbreak of mass reproduction of the Siberian silkworm in the mid-1950s. Then the silkworm damaged about 1.5 million hectares of taiga. The north-east of the region was especially affected.

The Siberian silkworm feeds on the needles of almost all coniferous species found within its range. Prefers larch, often damages fir and spruce, to a lesser extent Siberian and common pines.

The development cycle of the Siberian silkworm usually lasts two years.

In the second half of July, the summer of butterflies begins, it lasts about a month. Butterflies don't eat.

The female lays on average about 300 eggs, placing them one by one or in groups on needles in the upper part of the crown.

In the second half of August, caterpillars of the first age emerge from the eggs, they feed on green needles, and in the second or third age, at the end of September, they leave for wintering. Caterpillars overwinter in the litter under the cover of moss and a layer of fallen needles.

The rise in the crown is noted in May after the snow melts. Caterpillars feed until next autumn and leave for the second wintering at the fifth or sixth age. In spring, they again rise to the crowns and after active feeding in June weave a dense gray cocoon, inside which they then pupate. The development of the silkworm in the chrysalis lasts 3-4 weeks.