Silkworm that eats coniferous trees. Why is the Siberian silkworm dangerous? give to nuts

© Grodnitsky D.L.

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 of the voracity of the locust, which, during mass reproduction, unites in multi-million flocks, flies hundreds of kilometers in search of food, and in a matter of hours destroys grain and cotton crops, orchards and vineyards, 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, mass reproduction, although less known, is a real disaster. voracious insect- Siberian silkworm ( 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, and the rest develop freely, 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. Winters in the litter and worst enemy silkworm - microscopic egg-eater telenomus ( 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 O 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 consequences of outbreaks in these two types of forests are quite different because different types trees tolerate the invasion of the silkworm 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 adverse conditions growth: 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 only 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), have 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 light birch 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 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 total area 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 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 today 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 effect will the astronomical amount of decay and combustion products emitted into the atmosphere have on climatic 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. Therefore, 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 - the root forest formation - arise in the conditions of permanent large breeding centers of the silkworm? Another explanation looks more realistic: the 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 agricultural and logging activities man, which 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 herbaceous 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 successional system returns to its original state, then there is a possibility of the capture of the ecological space by other species that will not allow further change of 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 concept is repeated: the consumer of the first order translates 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.

Forest pests in the Baikal Reserve.
Siberian silkworm

Research abstract

Pine cocoon moth: 1 - male; 2 - female; 3 - caterpillar; 4 - cocoon

Lake Baikal... Millions of people know it today. There is no other lake on earth like the sacred Baikal glorified in legends and songs. Everything is unique in it - water, vegetation, rocky shores and majestic spurs of ridges framing it. In order to preserve this priceless gift of nature for our descendants, we must carefully treat everything connected with Baikal.

In 1969, in the central part of the Khamar-Daban ridge, the Baikal state reserve with a total area of ​​166 thousand hectares, later received the status biosphere reserve with inclusion in the international network of protected areas. The main tasks of its activity are the study natural processes, restoration of natural complexes of the southern coast of Lake Baikal and enrichment with hunting and commercial species of land adjacent to the lake.

The territory of the reserve is asymmetric due to the Khamar-Daban ridge stretching from west to east. The maximum height in its central part is about 2300 m above sea level. average temperature air on the coast of Lake Baikal in July +14 °С, in January -17 °С at average annual temperature-0.7 °С.

It is impossible to imagine the protected area without butterflies fluttering over the flowers, bewitching with their unique beauty. Among the butterflies there are species listed in the Red Book, such as, for example, Apollo, swallowtail. In the meadows, pigeons, urticaria, and nigella are common. Under the canopy of birch groves there are hawks and bears. With the onset of dusk and before dawn, numerous representatives of scoops, graceful moths, corydalis gather at light sources.

Insects are the most numerous group of animals in the reserve. They can be found in the air, and on the ground, and in water, and in the soil. Of the dangerous pests of the forest stand, there are Siberian silkworm, willow volnyanka, gypsy moth. Their mass reproduction can lead to partial or complete drying of forests.

In 1869, Truvello, a scientist from Massachusetts, brought the eggs of the Siberian silkworm to the United States ( Dendrolimus sibirecum). several tracks were lost. After some time, this led to the mass reproduction of the silkworm, whose caterpillars laid bare forests and gardens in Massachusetts, and in 1944, despite the struggle against them, they occupied all of new England.

The first information about the Siberian silkworm in the forests of the Baikal region was published by K.A. Kazansky in 1928. According to D.N. Frolov, in 1948, in the Kultuk forestry alone, the Siberian silkworm led to the drying up of 24,670 hectares of valuable cedar plantations. Outbreaks of mass reproduction of the Siberian silkworm were also noted in other areas of the Baikal basin.

The Siberian silkworm is a large butterfly with a wingspan of 60–80 mm for the female and 40–60 mm for the male. Color varies from light yellowish brown or light gray to almost black. The forewings are crossed by three darker stripes. In the middle of each wing there is a large white spot, the hindwings are the same color.

The revision of the genus showed that the Siberian silkworm is a subspecies of the large coniferous silkworm ( Dendrolimus superans Butl). Since the Siberian silkworm can only be recognized as a subspecies, its ecological and morphological forms should be considered tribes.

There are three such tribes on the territory of Russia: larch, cedar and Ussuri. The first occupies almost the entire range of the subspecies. Cedar and Ussuri have a limited distribution.

Immediately after mating, females lay their eggs on needles, mainly in the lower part of the crown, and during periods of very large numbers - on dry branches, lichens, grass cover, forest litter. In one clutch, there are usually several dozen eggs (up to 200), and in total the female can lay up to 800 eggs, but most often the fecundity does not exceed 200–300 eggs.

The eggs are almost spherical in shape, up to 2 mm in diameter, at first bluish-green in color with a dark brown dot at one end, then grayish. Egg development lasts 13–15 days, sometimes 20–22 days.

caterpillars vary in color from gray-brown to dark brown. The body length of the caterpillar is 55–70 mm, on the 2nd and 3rd body segments they have black transverse stripes with a bluish tint, and on the 4th–120th segments there are black horseshoe-shaped spots.

The first molt occurs after 9-12 days, and after 3-4 - the second. At the first age, the caterpillars eat only the edges of the needles; at the second age, they eat the entire needles. At the end of September, the caterpillars burrow into the soil, where they curl up in a ring and hibernate under a moss cover.

At the end of April, the caterpillars climb into the crowns of trees and begin to feed, eating whole needles, and with a lack of food, the bark of thin shoots and young cones. About a month later, the caterpillars molt for the third time, and in the second half of July - again. In autumn they leave for the second wintering. In May-June of the following year, adult caterpillars feed intensively, causing the greatest harm. During this period, they eat 95% of the food necessary for full development. They molt 5–7 times and go through 6–8 instars accordingly.

Caterpillars feed on the needles of almost all conifers. In June, they pupate; before pupation, the caterpillar weaves a brown-gray oblong cocoon. The pupa, 25–45 mm long, is initially light, brownish-red, then dark brown, almost black. The development of the pupa depends on temperature and lasts about a month. The massive summer of butterflies takes place in the second decade of July. On the southern slopes of the mountains, it passes earlier, on the northern slopes - later.

The development cycle of the Siberian silkworm usually lasts two years, however, in the south of the range, development almost always ends in one year, and in the north and in high-mountain forests, sometimes there is a three-year generation. With any phenology, the main periods of the life of the Siberian silkworm (years, development of caterpillars, etc.) are very extended.

Heat plays a decisive role in determining the duration of the development cycle; weather and climate in general, as well as the timely passage of diapause by caterpillars. Characteristically, the transition to a one-year cycle of development in places with a two-year generation is observed most often during an outbreak of mass reproduction. It is also believed that a one-year development cycle occurs if the annual sum of temperatures exceeds 2100 °C. At a sum of temperatures of 1800–1900°C, the generation is two-year, and at 2000°C, it is mixed.

Silkworm years are observed annually, which is explained by the presence of mixed generations. However, with a pronounced two-year development cycle, flying years occur every other year.

Silkworm damages 20 species tree species. It appears in mass in different years and is characterized by variable forms of the gradation curve. Most often, silkworm outbreaks occur after two or three dry growing seasons and the strong spring and autumn forest fires that accompany them.

In such years, under the influence of a certain way of evolving metabolism, the most viable and prolific individuals appear, successfully enduring difficult periods of development ( younger ages caterpillars). Forest fires contribute to the reproduction of the pest, burning the forest floor, in which the entomophages (telenomus) die. In lowland forests, silkworm outbreaks are usually preceded by harsh winters with little snow, leading to the freezing of entomophages, which are less cold-resistant than silkworm caterpillars. Outbreaks occur primarily in forests thinned by cuttings and fires, near raw material bases at a low density of stands of different age and composition. Most often these are overmature and ripe, less often middle-aged pure stands with a rare undergrowth and a slight admixture of hardwoods.

At the beginning of the outbreak and during periods of depression, the silkworm has a clear commitment to certain types of forest, landforms, phytoclimate and other ecological features of plantings. Thus, in the flat part of Western Siberia, the centers of population outbreaks are most often associated with fir, oxalis and green moss. In the zone of coniferous-deciduous forests of the Far East, they are associated with mixed cedar and cedar-fir plantations, and in Eastern Siberia their location is closely related to the relief features of mountain forests and the dominance of larch and cedar.

In terms of nutritional value for caterpillars, larch needles are in first place, then fir needles, cedar needles take only third place. Therefore, in larch forests, the fertility and breeding energy of butterflies is the highest, and in cedar forests - average. Caterpillars are rapidly developing in fir forests according to an annual cycle, but to the detriment of fertility, which falls to average values. When feeding on spruce and pine needles, there is a rapid grinding of individuals, a drop in fertility and survival.

Outbreaks of mass reproduction last 7–10 years, of which 4–5 years the plantations are significantly damaged, the stands bare by caterpillars dry out and are populated by stem pests.

The most unstable species in the taiga is fir (Siberian, white-pored), the most stable is larch (Siberian, Dahurian, Sukacheva).

In the first year of severe caterpillar damage to coniferous trees, the latter are populated by stem pests only when they are completely deneedled. In subsequent years, their number and activity first increase rapidly, and after 2–4 years, a sharp decline begins.

The Siberian silkworm is an enemy of the taiga forests, and the losses it inflicts are comparable to those from forest fires. The area of ​​distribution of the silkworm extends from the Urals to Primorye, including Mongolia, Sakhalin, the Kuril Islands, part of China, Japan and North Korea. Supervision of the Siberian silkworm should be concentrated in the places of the most active breeding of the silkworm and should be carried out with particular care after dry periods, which favor an increase in numbers. It must necessarily include aerial reconnaissance of areas with an increasing number of pests and ground forest pathological surveys, as well as accounting for caterpillars and flying butterflies.

The active centers of mass reproduction of the Siberian silkworm were first identified in the northern regions of Buryatia in larch, larch-pine plantations of the Angarsk forestry enterprise. The area of ​​focal distribution of the silkworm on the northeastern coast of Lake Baikal (Baikal, Nizhneangarsk and Florikhinsk groups of outbreaks), according to the forest pathological survey of 1980, amounted to over 100 thousand hectares. Increased numbers of silkworms in 1981–1986 it was also noted in the forests of the southern regions of Buryatia (Dzhidinsky, Kyakhtinsky, Bichursky forestries).

The peculiarity of the climatic and forest-ecological conditions of the Baikal forests determines the regional features of the ecology and biology of this pest. Everywhere the development of the silkworm proceeds according to a two-year cycle; in the forests of Khamar-Daban, the entomologist Rozhkov noted a three-year generation. The development of the silkworm by one-year generation is possible only in larch forests growing in the zone of Southern Transbaikalia. The Baikal and Transbaikal populations of the Siberian silkworm are characterized by the simultaneous existence of two generations, each of which develops according to a two-year cycle. The level and ratio of the number of these generations may be different, but most often one of the generations dominates. In this regard, the mass years of the Siberian silkworm butterflies in some populations are observed in even years, and in other populations - in odd years.

Thus, in terms of the frequency of outbreaks of mass reproduction and the area of ​​focal distribution, the Siberian silkworm is the most dangerous pest of the coniferous forests of the Baikal basin.

Entomologist N.A. Belova.

Literature

Mikhalkin K.F. Baikal Reserve.

Fauna of the forests of the Baikal basin. – USSR Academy of Sciences, Siberian Branch, V.N. Sukachev.

Atlas-determinant of insects.

Let's talk about Siberian silkworm- This is a species of butterfly that lives in coniferous forests. It is quite large in size, for example, its wingspan reaches sixty - eighty millimeters for the female, and forty - sixty centimeters for the male. It belongs to the family of cocoons. Its caterpillars feed on coniferous trees. She especially prefers such trees as: larch, spruce, ordinary pine and fir.

A distinctive feature of the male is his antennae, they have a feathery shape. Butterfly wings are brown with different shades: yellow, gray and black. The front wings, if you look closely, have three stripes, usually dark in color, and in the middle there is a large speck white color. The wings that are behind are mostly one-color.

Butterflies begin to fly from mid-July, and their flight lasts until mid-August.

What kind of eggs do they have? About two millimeters in diameter, in the form of a ball. If you look at them, then on each egg you can see a brown dot, and the color of the eggs itself is green with blue and turns into gray. There may be thirty, forty or more in one clutch, sometimes up to two hundred. Eggs develop over about thirteen days, sometimes up to twenty-two. After that, from mid-August, a caterpillar comes out, its food is needles. She lives for herself, feeds and develops into a more adult individual. In the month of September, towards the end, the caterpillar prepares for wintering. It hibernates under moss and fallen needles, being in a state of complete rest. In the spring, when the snow has melted, the caterpillar crawls into the crowns, where it lives there all the time until autumn.

The length of the caterpillar is approximately fifty-five to seventy millimeters. It is usually brown or brown.

The caterpillar actively feeds and, having accumulated the necessary food elements, in June it wraps itself in cocoons, which are very dense and have a gray color. The pupa develops over a period of three to four weeks.

The pupae reach a length of twenty-eight centimeters - thirty-nine. The color of the pupa is light, then turns into brown, with time, as it grows, it becomes almost black.

In Russia, the Siberian silkworm lives within the Urals, also in Siberia, where there are especially many coniferous trees. It spread over quite large area. It is also common in Asia: Kazakhstan, Mongolia and other countries. The difference in temperature does not frighten him much and therefore it is distributed from Siberia to Asia and beyond. This type of silkworm is considered a pest of forest trees. The distribution of the Siberian silkworm to the west is also noted.

At Siberian silkworm there are enemies - these are riders, braconids, egg-eaters, ibraconids. These natural enemies destroy the Siberian silkworm, regulating their numbers. He has something to eat, where to live, he breeds, like everything else in nature, and has his enemies. Such a description revealed more to us the diverse and surprisingly harmonious world of nature.

A dangerous pest of forests and cultural plantations, the gypsy moth has a wide distribution area. This pest can be found in Asia, Europe, North Africa, North America. It covers the entire territory of Russia, is found in the south, in Siberia and Far East. Deciduous trees are especially affected by caterpillars. In the absence of food, silkworms move to young coniferous trees. Once in the nursery, insects can cause significant damage to plantings.

What does a gypsy moth butterfly look like

The gypsy moth is a butterfly belonging to the Lepidoptera order from the family of volnyanka. Distinctive feature of these insects, there are noticeable differences between males and females.

Differences in adults are noticeable in color and shape:

1. Females - the size of the wings in the unfolded state reaches 90 mm. The thick body has the shape of a cylinder. A grayish fluff is visible on the abdomen. The antennae are thin and long.
2. Male - wingspan 40-50 mm, body thin, covered with hairs. The color of the wings is brown, the surface is covered with a pattern of dark spots and broken lines. Antennae combed.

Gypsy moth butterflies prefer woodlands, dry places with enough light. The first centers of distribution are usually located on the edges. During droughts, large outbreaks of mass reproduction of silkworms occur. This species is the leader among pests in terms of the number of breeding outbreaks and the duration of these periods.

Silkworm breeding

Heavy females rarely fly, they sit on the bark of trees and attract males with the help of pheromones. Males start years a few days earlier. They are especially active in evening time. In search of a mate, they fly long distances. After fertilization, the females lay their eggs under the bark of trees at a height of 3-4 m. They are round, yellow or pinkish in color. Size - 1 mm, the number of eggs in the clutch of gypsy moth - 100-1000 pieces. In the egg state, the insect spends most of its life - about 8 months.

An embryo is formed inside the egg shell, which remains to winter. In spring, when the temperature rises to +10 0, the first caterpillars appear. For some time they sit motionless, then spread out over the tree. The body of small caterpillars is covered with bristles and air bubbles. This allows them to travel with gusts of wind. For movement over considerable distances, insects can release webs.

Interesting fact. The caterpillar is the only form of non-greenhouse that feeds, accumulating energy for the remaining phases of development.

The gypsy moth belongs to the cocoon moth family. The caterpillar appears with sixteen legs. At birth, it is light yellow, but quickly darkens and turns brown or black. There are several longitudinal rows of warts on the body.

Information. Gypsy moth eggs are extremely viable, they are able to withstand frosts down to -50.

After settling in a new territory, active feeding begins. Young caterpillars eat during the daytime, gnawing small holes in the leaves. After 3-4 months, they switch to eating at night, eating the leaf completely. In addition to foliage in the diet of pests, buds, young shoots, flowers. Depending on the climate zone caterpillars take 50 to 80 days to develop. Then they pupate. This occurs in June-July, the pupal stage lasts 10-15 days.

Information. Optimum temperature+20-25 for insect growth, if it drops to +10, development stops. Male caterpillars go through 5 larval stages up to the imago (adult) stage, females - 6 stages.

Distribution and harm

The pest has a wide distribution area. In Europe, it is found up to Scandinavia, in Asia it covers many countries: Israel, Turkey, Afghanistan, Japan, China, Korea. An interesting story of a butterfly getting into North America. The insect was introduced artificially for crossbreeding experiments with other species. The larvae were able to spread from the experimental area to open forests. The problem that arose was not given due importance, and over the course of several years, the non-partners captured a vast territory. Only in 1889, the gypsy moth was recognized as a pest. But the insect is already firmly entrenched in the new territory.

Interesting fact. Due to the wide range of distribution of butterflies, they are divided into races. In Russia, there are Far Eastern, European, Siberian and other races.

The gypsy moth caterpillar exposes deciduous trees in forests and gardens. She prefers fruit plantations of apple trees, plums, apricots. IN wild nature chooses oak, birch, linden. Bypasses ash and alder. In total, the pest eats about 300 plant species, including conifers. The main division occurs on the European and Asian races. The Asian group is a real polyphage, feeding on various types of trees and bushes.

Varieties of gypsy moths

Gypsy moth butterflies are classified as various types depending on where you live and how you eat. Common groups include:

This is a small representative of its kind. The size of the wings of females is 40 mm, males 30 mm. The insect is common in Europe and Asia. The caterpillar will grow up to 55mm and is gray-blue in color with white and yellow stripes. Pests live in colonies, create spider nests. When fighting the gypsy moth, it is necessary to cut and burn the branches where the ovipositor is seen. The trees themselves are sprayed with insecticides.

Male and female oddball

Walking silkworm

The marching silkworm is characterized by the ability of caterpillars to migrate to new feeding grounds. At the same time, they line up in a long chain, following each other. The first caterpillar, which is the leader, releases a silk thread along which the rest of the insects are guided. There are two types of marching silkworms - oak and pine.

Pine cocoonworm

Insects are common in the coniferous forests of Siberia and Europe. They damage pine plantations, less often than other species. Grayish-brown females are 85 mm in size, males - 60 mm, caterpillars - up to 80 mm. Caterpillars spend the winter in the ground under tree trunks. In the spring they rise to feed, pupate in July.

Siberian silkworm

The unpaired Siberian silkworm feeds on coniferous trees. This species damages spruce, pine, cedar and fir. The insect settled in the forest and forest-steppe zone of Siberia. The northern limit of its distribution runs along the Arctic Circle. The development of a silkworm from egg to butterfly in a cold region takes 2 years. IN warm years it can accelerate to a one-year cycle. Butterflies of the Siberian silkworm are distinguished by a variety of colors. There are adults of brown, gray, black color. The wingspan of females is 6-10 cm, males are more modest in size - 4-7 cm. Three dark jagged stripes run across the front wings. Hind wings are brown. The head and thorax are the same color as the forewings.

The clutch of butterflies is bluish in color, the size of the eggs is 2 mm. They are deposited in uneven piles of 100 pieces. They are located in the bark, on needles and twigs. When the larva appears, it eats half of the shell. Caterpillars grow up to 11 cm, their bodies are gray or black. There are blue hairs on the back. Insects are able to take a threatening posture. At the same time, they raise the front of the body and bend their heads. A bright stripe runs along the sides yellow color. The body is covered with hairs, they are the longest in the front and on the sides.

The head of the caterpillar is brown, with orange spots on the abdomen. The pupa of the Siberian silkworm is dark, almost black. Its length is up to 5 cm, the cocoon is suspended on branches or between needles. Burning hairs are woven into its shell. There are three races of local silkworms:

• larch;
• fir;
• cedar.

Silkworm caterpillars calmly endure the cold, they leave for wintering at a temperature close to 0 0. They crawl onto trees after wintering immediately after the snow melts. As it grows, frost resistance increases.

Information. With frosts down to -10, the caterpillars die, and they do not survive winters with little snow.

Pest Control Methods

Identification of the neparnik occurs by gnawed leaves, excrement, butterflies and ovipositors in the web. Basic information is taught by studying adults and the number of eggs in a clutch. This provides information for the forecast, allows you to determine the phase of the outbreak. Methods of pest control are chosen depending on the degree of their distribution.

Attention. The Siberian and Far Eastern races of silkworms represent a quarantine danger. A thorough inspection of goods and vehicles following from Siberian region. Pests are lured out with pheromone traps.

How to deal with gypsy moth in your garden? Trees should be carefully monitored. When signs of damage by caterpillars appear, start the destruction of the ovipositors. They are visible among the foliage, nests are cut and burned along with eggs. Caterpillars can be harvested by hand, a tedious procedure that can be done in small areas. Effective method- the device of glue rings, crawling caterpillars will stick to the surface of the traps. In autumn, egg clutches are scraped from the bark of trees.

Attention. Wear protective gloves when handling pests.

The use of insecticides is the most effective measure to control the gypsy moth in the garden and woodland. At the beginning of spring, trees are treated with Chlorophos, Metaphos, as well as organophosphorus compounds.

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.

In the Amur region, the Siberian silkworm was discovered in the Blagoveshchensk region in 2008. Compared to other entities Russian Federation located on the territory of Siberia and the Far East, the situation for the Siberian silkworm is quite favorable here. However, do not be hopeful, because. even a single silkworm can create a serious problem.

Periodically, about once every 10 years, there is an outbreak of the Siberian silkworm, the consequences of which are the destruction of vast areas of valuable coniferous plantations. The use of modern insecticidal pyrethroid and bacterial preparations in last years allowed to partially localize the foci of the pest and stop its further spread.

At the same time, the danger of a new mass reproduction of the Siberian silkworm remains.

Periodic large-scale outbreaks of mass reproduction of the Siberian silkworm, due to the biological characteristics of this species, lead to significant changes in the structure of taiga forests, the destruction of forest stands and a change in forest formations.

The centers of mass reproduction are noted in Russia annually on an area from 4.2 thousand to 6.9 million hectares and cause significant damage to forestry. This has already happened in the Far East and Siberia. The coniferous forest in these areas is simply amazing in 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.

For the timely detection of breeding centers, satellite monitoring is used.

In the period between outbreaks, the silkworm lives in reservations - areas with the most favorable development conditions. In the zone of dark coniferous taiga, the reservations are located in mature, quite productive plantations of forb-green-moss forest types with the participation of fir.

Outwardly, the Siberian silkworm is a large butterfly with a wingspan of 60-80　mm for the female and 40-60　mm for the male. Color varies from light yellowish brown or light gray to almost black. The forewings are crossed by three darker stripes. In the middle of each wing is a large White spot, hind fenders single color.

Females lay eggs on needles, mainly in the lower part of the crown, and during periods of very large numbers - on dry branches, lichens, grass cover, and forest litter. In one clutch there are usually several dozen eggs (up to 200), and in total the female can lay up to 800 eggs.

Caterpillars of the Siberian silkworm have different colors. It varies from gray-brown to dark brown. The body length of the caterpillar is 55-70 mm, on the 2nd and 3rd body segments they have black transverse stripes with a bluish tint, and on the 4-120th segments there are black horseshoe-shaped spots.

At the end of April, the caterpillars climb into the crowns of trees and begin to eat whole needles, and with a lack of food, the bark of thin shoots and young cones. In autumn they leave for the second wintering. In May-June of the following year, adult caterpillars feed intensively, causing the greatest harm. During this period, they eat 95% of the food necessary for full development.

The Siberian silkworm damages about twenty species of coniferous trees - from larch to spruce. But they prefer fir, spruce, larch. Cedar is damaged to a lesser extent, pine is even less damaged. In June, caterpillars pupate; before pupation, the caterpillar weaves a brown-gray oblong cocoon. The massive flight of butterflies occurs in the second decade of July and lasts about a month.

Butterflies don't eat. The female lays on average about 300 eggs, placing them singly or in groups.

In the period between outbreaks, the silkworm does not cause serious damage: its number is 1-2 caterpillars per tree, and caterpillars can not be found on every tree.

In the dark coniferous taiga, silkworm foci form after several years of hot, dry weather in summer.

The main danger of the outbreak of the Siberian silkworm is not only that an average of 0.8 million hectares are destroyed annually from the Siberian silkworm, but also that the forests that died from the silkworm are poorly restored. Caterpillars destroy the undergrowth along with the forest stand, and only a decade later, a small undergrowth of deciduous species may appear. In old foci, conifers appear only 30-40 years after the drying of forest stands, and not everywhere and not always.

Even if the forest is not completely destroyed by silkworms, damaged plantations (“silkworms”) later become foci for forest stem pests, primarily black coniferous barbels, as well as bark beetles, borers, and horntails. In turn, they can significantly expand the initial drying zone of the forest, moving to completely healthy trees.

getting worse qualitative composition stand.

If you find a Siberian silkworm on the coniferous trees of your site, you must immediately organize measures to combat this pest.

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.

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 along coniferous forests 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.

In case of detection, it is necessary to contact the Amur branch of the Federal State Budgetary Institution "Zabaikalsky Reference Center of the Rosselkhoznadzor" for the necessary processing.

Registration of quarantine phytosanitary documentation for the export of timber products and timber from the territory infected with quarantine objects is carried out by the Office of the Rosselkhoznadzor according to Trans-Baikal Territory and the Amur Region in accordance with the Federal Law of July 15, 2000

N 99-FZ "On Plant Quarantine", Decree of the Governor of the Amur Region dated April 13, 2009 N 187 "On the imposition of quarantine on the Siberian silkworm in the Blagoveshchensky District", as well as the order of the Ministry Agriculture of the Russian Federation dated March 14, 2007 No. 163 "On the organization for the issuance of phytosanitary certificates and quarantine certificates". Permits are issued based on the conclusion issued by the Amur branch of the Federal State Budgetary Institution "Zabaikalsky Reference Center of Rosselkhoznadzor" on the quarantine phytosanitary status of regulated products.