The Siberian silkworm is a butterfly of the cocoon moth family. This is a dangerous pest, the object of which is the destructive attention of coniferous trees. Silkworms are most harmful to cedar, fir, and larch, less so to pine and spruce.

The needles are eaten not by butterflies, but by Siberian silkworm caterpillars - they destroy it entirely, and if there is a lack of food, they switch to shoots and young cones.

Silkworm development is bisexual; in winter, the caterpillars hide in a layer of fallen leaves and dry grass. The full development cycle of the silkworm lasts 1-2 years in the southern part of its habitat, in other regions – two or three years. Over the course of three years, the silkworm develops in the northern and high mountain regions.

As a rule, the periods of life of the Siberian silkworm depend on the ambient temperature and the timing of the caterpillar's passage through the period of physiological inhibition of metabolic processes - diapause.

The Siberian silkworm is a quarantine object - harmful to the body of plants and causing damage to them, with limited distribution in the country, and requiring special control measures.

Insect structure

The wingspan of the butterfly is 60-95 mm, the labial palps are shortened, and are abundantly pubescent. The third segment has a smoothly rounded apex and is 1/3 the length of the second segment. The eyes are hemispherical, naked. There are spurs on the middle and hind tibiae. On the front wings the edges are smooth, slightly rounded. The hind wing has a basal cell; the humeral veins are absent.

The color of the wings of the Siberian silkworm butterfly ranges from light gray to dark brown. It can also be ocher-brown, dark or light brown. On the front wings there is a white spot and two dark transverse bands.

The internal ligation is most often incomplete, visible only in the first half of the wings. External - difficult to see from the inside, has teeth on the outside.

Butterflies have differences in wingspan - in males it is 78-96 mm, in females it is 60-76 mm.

The eggs are round, 2.2 mm in diameter. The cover of the egg is at first light green with a brown dot on one side. Over time, the egg becomes darker.

The caterpillar has a body without spines and warts. The hairline consists of thick, velvety hairs, and long sparse hairs, which are 10 times longer than short ones. On the second and third segments of the body, the Siberian silkworm caterpillar has black and blue transverse stripes, and on the fourth and twelfth segments there are rounded black spots. The length of the caterpillar is 5-8 cm.

The pupa at first is distinguished by light or red-brown integuments, then they become dark brown or black.

Stages of development of the Siberian silkworm

First instar butterflies appear at the end of June, and they become especially active at sunset. “Newborns” do not need additional nutrition; their body has accumulated enough nutrients from previous periods of life. Under the influence of the wind, young butterflies can fly 13-15 kilometers from the place of birth.

Mass mating begins in mid-July and lasts until early August. After mating, females lay eggs on the needles - one at a time or in whole groups. Sometimes dry branches, lichens, grass, and forest litter become places for laying eggs. One clutch can contain up to 200 eggs. The most fertile females can lay up to 300 eggs.

Embryo development lasts 13-15 sometimes 22 days.

At an early age, the larva feeds on the tips of needles, but in the second age it is able to eat the whole needle. Caterpillars especially love soft larch needles; feeding on spruce and pine needles leads to smaller individuals, decreased fertility, and even complete extinction.

At the end of September, the caterpillars leave the trees, burrow into the soil under the moss, and spend the winter there, curled up in a ring. As a rule, they spend the winter in the third or second instar, depending on the type of forest in which they grew. In total, the Siberian silkworm molts 5-7 times and survives 6-8 instars.

In the spring, at the end of April, the caterpillars wake up, climb the trees and begin to feed on needles, shoot bark, and young cones. At the end of May they begin their third molt, and in July - the fourth. In the fall, the caterpillars again go to winter, so that with the onset of warm weather they will again begin intensive feeding. It is at this age that they cause more damage to the forest, eating up to 95% of the food they need for final development. Older individuals, in search of food, can crawl through treeless space for a distance of up to one and a half kilometers.

A full-fledged, developed caterpillar, having survived all the necessary ages, begins to weave a dense gray cocoon, inside which it becomes a pupa. The development of the pupa lasts 3-4 weeks.

At the end of June, a sexually mature individual of the Siberian silkworm emerges from the cocoon, ready for mating. And the whole cycle repeats again.

Distribution area of ​​the Siberian silkworm:

The insect is distributed in Siberia, Eastern Siberia, the Far East and the Urals. The silkworm eats pine needles and causes damage to coniferous forests over a fairly wide area from the Southern Urals to Vladivostok, from Yakutsk to Mongolia and China, where it is equally widespread.

There are Siberian silkworms in Kazakhstan and North Korea; the southern border of its distribution is at 40 degrees north latitude. Scientists note an expansion of the range to the north and west.

Damage from silkworms and means of combating them

Most often, in summer, outbreaks of mass reproduction occur over an area of ​​4-7 million hectares, and cause serious damage to forestry. In addition, the mass reproduction of silkworms leads to an outbreak of secondary pests - bark beetles, borers and longhorned beetles.

The Siberian silkworm is also present in healthy forests, but in limited quantities. An environmental disaster can be triggered by the mass reproduction of a pest, and drought is considered one of the reasons for this phenomenon. During drought, the caterpillar is able to develop in a year, and not in two years as usual. Due to the sharp increase in the population, the natural enemies of the silkworm do not have time to destroy them. Early spring fires also contribute to the spread of the pest, because they also destroy the telenomus insect, which eats silkworm eggs. The natural enemies of the Siberian silkworm are birds and fungal infections.

The entomological state of the forest is monitored by instruments from space satellites; it is they that contribute to the timely identification of breeding sites and allow the necessary measures to be taken.

In the mid-90s, in Eastern and Western Siberia and the Far East, the Siberian silkworm damaged green spaces over a wide area. In the Krasnoyarsk Territory, an outbreak that lasted four years caused damage to forests in 15 forestry enterprises on a total area of ​​600 thousand hectares. Then silkworm caterpillars destroyed cedar plantations, which are of great value to the national economy.

Over the past hundred years, 9 outbreaks of silkworms have been observed in the Krasnoyarsk Territory. As a result, forests covering an area of ​​ten million hectares were damaged. The outbreak was localized using modern insecticides. However, the outbreak can flare up at any favorable time.

As a rule, the Siberian silkworm waits in the wings in places with fairly favorable conditions for development. In the dark coniferous taiga, its reservations are located in mature and productive stands with a large “food supply.”

The pest spreads not only naturally, but also by moving to a new place by means of transport as a “hare”, hiding under the bark of logs and other timber, as well as in seedlings and saplings - of course, this is how non-adult butterflies, cocoons and eggs move.

Therefore, bans and restrictions on imported forest products have been introduced in the phytosanitary zone:

Coniferous tree logs must be debarked and disinfected with pesticides. The absence of silkworms and other pests is confirmed by a special certificate.

Planting material, bonsai, and branches of coniferous trees are prohibited from being imported from the phytosanitary zone from May to September without a quarantine certificate. If there is no certificate, all materials must be destroyed within 5 days of discovery.

In areas where silkworms are spreading, ground or aerial treatment of forests with pyrethroids, neonicotinoids, and organophosphorus compounds is carried out.

In addition, the number of pests is recorded using pheromone traps or by counting caterpillars in tree crowns.

Good results are obtained by preventive treatment of forests with special preparations in the summer.

Siberian silkworm (cocoon moth) – Dendrolimus sibiricus Tschetw

Damages

Silkworm caterpillars in different parts of its wide range feed on the needles of various coniferous tree species, preferring the needles of larch (Daurian, Sakhalin, Siberian, Sukachev), fir (Siberian, Sakhalin and whitebark) and cedar (Siberian and Korean). Less willingly, usually when growing together, the caterpillars feed on the needles of spruce (Siberian and Ayan), Scots pine and dwarf cedar.

Maliciousness

One of the most harmful types of pine-eating pests.

Spreading

The Siberian silkworm is widespread in the forest and forest-steppe zones of Siberia - from the Urals to Sakhalin, Kunashir and Iturup inclusive (Kuril Islands). The northern border of distribution - from the White Sea to the Penzhina Bay - coincides with the Arctic Circle, not reaching it in the European part of Russia and east of 145°. The southern border of distribution in the European part of Russia and Western Siberia coincides with the southern border of distribution of Sukachev larch and Siberian larch; further to the east it passes into the northwestern regions of China, Mongolia, the northeastern regions of China and Korea.

Preferred stations

Reservations and primary foci of silkworms are confined to plantings that are more well heated and aerated, with drier growth conditions or with well-drained soils, average density (0.4 - 0.7) or to their outskirts, edges, open spaces, often to clean plantings , older age classes belonging to groups of drier or fresher forest types (green mosses, forbs, etc.). They are located: in the flat taiga - along the topography, in low mountains (up to 500 m in height) - on plateaus and along slopes, in the lower and mid-mountain taiga of higher mountains located in northern or humid areas - along the slopes of southern points, and in southern or dry areas - along the slopes of other directions. In plantations disturbed by logging, especially clear-cutting, forced-selective and other unmanaged logging, xerophytization of plantings occurs, which favors the constant nesting of silkworms and the transformation of plantings into primary foci during droughts. The same xerophytization of plantings and destruction of natural biogeocenoses in them occurs, especially with intensive grazing of livestock in them, in the vicinity of large settlements

Generation

Everywhere in the silkworm habitat in our country, a 2-year generation has been registered. Nowhere has the annual generation been established as constant for a given area. However, in warm years, in which the growing season lengthens. An earlier period, beginning earlier in the spring and extending into later autumn, creates conditions favorable to the feeding and faster development of the silkworm. The butterfly's life begins earlier, the laid eggs develop faster, the emerging caterpillars feed longer, go to winter at an older age, next year they emerge from winter earlier and manage to complete their development completely within a year. Since the development of the outbreak is confined to a period of warmer, sunny and drier years, in these same years a transition in the development of silkworms in Western Siberia from a 2-year to a one-year cycle was noted. It should be emphasized that such a transition was more often observed in the fir race, which is distinguished by its smaller size and fewer instars during the caterpillar stage.

P.P. Okunev (1961) suggests that in areas located north of the July isotherm of +18°, the Siberian silkworm develops on a 2-year cycle. In areas south of the July isotherm of +20°, development proceeds according to an annual cycle. In areas located within the boundaries between the named isotherms, development proceeds according to a variable cycle: in inter-outbreak years, as colder ones, according to a 2-year cycle, and in outbreak years, with warmer weather, according to an annual cycle.

Population structure. With a 2-year generation, two tribes of Siberian silkworms can exist in parallel in the same area, one of which flies in odd years, and the second in even years. The number of these tribes and its ratio can be different, which is of great importance for supervision and struggle.

Diagnostic signs

Siberian silkworm eggs

Siberian silkworm caterpillar

Butterflies

especially during periods of mass reproduction, they are so diverse in color and size that it is difficult to pick a pair of butterflies that are completely similar to each other. Females have short combed antennae and a thick body; their wingspan is from 6 to 10 cm. Males have clearly combed antennae and a more slender body; their wingspan is from 4 to 7.5 cm. The forewings of both sexes are light brown or light gray to almost black. Three jagged stripes run across them; one along the outer edge of the snout, the second near its middle and the third closer to its base. In close proximity to the dark stripes, often along the outer edge of the wing, there are whitish stripes consisting of semilunar spots and strokes. The field between the main and median stripes is often darker in color. Sometimes the main and median stripes are weakly expressed or even completely absent. Near the middle of the main stripe there is a semi-lunar white spot, which is always present in butterflies. The hind wings are light brown without a pattern. Below, both pairs of wings are brown, and there is one wide dark brown curved band running along them. The head and chest are colored similar to the front wings, the abdomen is similar to the hind wings.

Testicles

spherical, 2.0×1.5 mm in size, with a dark dot at the apex. Freshly laid eggs are bluish-green, then turn grey. They are smaller and somewhat lighter than those of the pine silkworm, they are deposited in irregular groups from several to 100 pieces and mainly on needles, twigs, twigs, the bark of branches and trunks. When the caterpillar emerges from the egg, it eats part of the shell.

Caterpillars

up to 11 cm long, varied in color - from gray to almost black. On the meso- and metanotum there are transverse bands of steel-blue burning hairs that open wide when the caterpillar raises the front part of the body and bends its head (threat pose). On the next seven abdominal tergites there are dark horseshoe-shaped spots. The dorsal side and spots on the sides are covered with silvery-white spear-shaped scales, developed to varying degrees in individuals. On the sides of the body, areas of skin are ocher-yellow, sometimes forming an almost continuous stripe. The body is covered with hairs, the longest and densest on its sides and in front on the prothorax. The head is round, matte, dark brown. Ventral side between legs with yellowish-brown or orange spots, not forming a continuous stripe.

The stool of the caterpillars is cylindrical, with six longitudinal and two transverse grooves, very similar to the stool of the pine silkworm. The pieces of needles in it are hardly noticeable.

Doll

up to 5 cm long, pitch-brown to black. Cremaster in the form of a transverse convex plate, densely covered with very small rufous hooked and simple setae. The last segments have short and sparse hairs. The pupa rests in a parchment-like, brownish or dirty-gray cocoon, into which tufts of blue, burning caterpillar hairs are woven, giving the cocoon its burning properties. Cocoons are located on branches, between needles, on trunks.

At the beginning of mass reproduction, dark-colored individuals of butterflies and caterpillars dominate, as in other mass needle- and leaf-eating insects.

Races

The question of the races of the Siberian silkworm remains unresolved. But, apparently, three races can be distinguished: larch, cedar and fir. In the process of the historical development of the species, these races not only adapted to feeding on the needles of the corresponding tree species, but also to the entire complex of forest-ecological conditions created by these species in forest stands. The named races of silkworms differ from each other in different amplitudes of size and weight at different stages of development, the number of caterpillar molts, speed of development and other characteristics. The names of these races are left here for ease of presentation.

Siberian silkworm caterpillars overwintering in the litter

Siberian silkworm cocoons

Complete consumption of Dahurian larch needles by Siberian silkworms

Phenology

First year of development

years of butterflies – June (3), July (1-3), August (1); eggs – June (3), July (1-3), August (1-3); caterpillars – July (2.3), August – March (1-3);

Second year of development

caterpillars – April – March (1-3);

Third year of development

caterpillars April – June (1-3), July (1); pupae – June, July (1-3); years of butterflies - June (3), July (1-3), August (1).

Note: ten days of the month are indicated in brackets

With one-year development, the second year falls out of the scheme, when the silkworm remains in the caterpillar stage throughout the entire growing season. On the contrary, when development is delayed to 3 years, the silkworm remains in the caterpillar stage not only during the second, but also the third growing season and completes development in the first half of the fourth growing season. Caterpillars that produce males molt from four to six times during development, and those that produce females molt from five to seven times; respectively, males have from five to seven, and females from six to eight instars.

Caterpillars developing on fir (S.S. Prozorov, 1952) have the following head width in mm: 1.0; 1.5; 2.0; 2.5; 3.5-4.0; 4.5-5.0, respectively, from the first to the sixth instars.

Caterpillars developing on cedar or larch (V. G. Vasiliev, 1940) have the following head width in mm: 0.9-l.0; 1.4-1.6; 1.8-2.2; 2.5-3.2; 3.5-4.2; 4.5-5.2; 5.5-6.2; 6.5-7.2, respectively, from the first to the eighth ages.

From the above it follows that there is almost no difference in the width of the head of caterpillars fed on different species within individual instars, but the number of instars in caterpillars fed on fir is 6, in caterpillars fed on cedar - 7, and fed on larch - 8. When feeding on larch caterpillars reach the largest sizes and produce the most well-fed and fertile individuals (pupae up to 6 grams and butterflies laying up to 826 eggs). However, caterpillars of the larch race, with a lack of food, are able to complete their development at the V (males) and VI (females) instars. But even in this case, they produce heavier pupae and fertile butterflies compared to the cedar and fir races.

During the period of their development, caterpillars of the fir race eat 46.5 g of needles (7185 needles), and 95% of it is consumed in the 5th and 6th instars (S.S. Prozorov, 1952). For other breeds, feed standards remain unstudied.

On the issue of the sum of effective temperatures required for the full development of the silkworm, there are disagreements in the literature: S. S. Prozorov (1952) defines it at 2032 °, P. P. Okunev (1955) - at 1300 - 1500 °, Yu. P. . Kondakov (1957) - at 1200 - 1250°. This issue needs further research.

Siberian silkworm caterpillars are cold-resistant. This gives them the opportunity to leave for the winter late, at temperatures close to zero, and to rise early into the crowns after wintering, following the melting of the snow. However, with sudden and sharp drops in temperature (below -10°), the first instar caterpillars may die en masse. They also die in harsh winters with little snow in their wintering areas. With age, the cold resistance of caterpillars increases, therefore, the chances of their death from frost decrease. In humid wintering conditions and rainy weather, fungal and other diseases spread among the caterpillars, often leading to mass death. This explains the fact that in damp honeydews no centers of mass reproduction of silkworms are created, and the outbreak that has begun subsides under the influence of rainy and cool weather.

Death of dark coniferous forests from complete devouring by Siberian silkworms

Duration of the outbreak

Conflicting opinions exist in the literature about the duration of outbreaks. The development of an outbreak in the same planting (focus) with a 2-year generation is possible within 14 years, and with a one-year generation - within 7 years. An outbreak that develops with a changing generation duration may have an intermediate duration between these deadlines, i.e., when one part of the generations during the outbreak period develops on a 2-year cycle, and the other on a one-year cycle. In the literature you can find reports of shorter-term outbreaks - within 4 - 6 years.

Reconnaissance surveillance

When organizing surveillance, republics, territories and regions in which outbreaks of mass reproduction of the Siberian silkworm have been observed or may be observed can be divided into two halves by a line running through Sverdlovsk - Tyumen - Kolpashevo - Yeniseisk - Nizhne-Angarsk - Kumora-Bambuika - Sredny Kalar - Stanovoy Ridge to the Sea of ​​Okhotsk. North of this line, outbreaks are possible but have rarely been observed. To the south of it, to the border of distribution of larch, cedar, fir and spruce forests, outbreaks of mass reproduction of the Siberian silkworm were observed most often. The southern half includes forests on the islands of Sakhalin, Kunashir and Iturup. In the forests of the northern half, systematic supervision may not be carried out. When a period of intense droughts occurs, which also affects these forests, it is necessary to carry out control aerial surveys in them in the appropriate years with ground verification of the emerging foci.

The forests located in the southern half of the forestry enterprises or timber industry enterprises and their constituent forests can be divided into three groups: those located in high mountains or wetlands, in which outbreaks of mass reproduction of the Siberian silkworm are not observed; located in sparsely populated areas and in mid-mountain zones, in which outbreaks of silkworms are observed sporadically; located in populated areas of the southern part of the taiga zone, forest-steppe and steppe, as well as in the lower mountain zones, in which outbreaks of mass reproduction were observed most often.

carried out on the verge of two generations, i.e. annually in the presence of two generations, a silkworm or a mixed development cycle, or in even or odd years in the presence of one generation with a 2-year development cycle.

Detailed supervision

According to the outbreak phases, the weight of pupae and the fertility of butterflies change within the following limits.

In the first and second phases of the outbreak, the maximum weight of pupae in the larch race is 5.5 - 6.0 grams, in the cedar and fir races - 3.8 - 4.2 g; The fertility of butterflies in the larch race is 650 - 750 eggs, in the cedar and fir races - 400 - 460 eggs. The average indicators are respectively: 4.0 – 5.0 g; 2.8 – 3.3 g; 440 – 580 pcs.; 250 – 330 pcs.

In the third phase of the outbreak, the average weight of pupae in the larch race is 2.5 - 3.0 grams, in the cedar and fir races - 2.0 - 2.4 g; The fertility of butterflies in the larch race is 220 - 380 eggs, in the cedar and fir races - 150 - 200 eggs.

In the fourth phase of the outbreak, the average values ​​are respectively: 1.4 - 1.8 g, 1.5 - 1.8 g, 70 - 120 pcs., 80 - 120 pcs. The minimum indicators are: 1.0 g, 0.8 g, 25 pcs., 5 pcs.

When the first drought occurs in areas with an annual or variable development cycle of the Siberian silkworm, supervision should be strengthened and expanded to the remaining registered reserves. If there is a repeat drought, a detailed examination of the same reservations, as well as similar plantings, should be carried out. The transition from a 2-year development cycle to a one-year one in areas with a variable development cycle of the Siberian silkworm should itself be perceived as a signal of the need to strengthen and expand supervision. In areas with a 2-year development cycle, surveillance is strengthened and expanded after repeated drought or when ongoing surveillance provides clear evidence of an outbreak.

Repeated drought and indicators obtained during surveillance indicating the beginning of an outbreak should be taken as a signal that it is necessary to conduct control surveys in the above-mentioned second group of forests. Finally, the results of surveillance of other forest pests and even agricultural pests should be taken as a signal about the need to strengthen and expand surveillance, since droughts initiate the development of outbreaks of many pests. In this regard, for areas with an annual or variable development cycle, supervision of pests with double generation (for example, common and other pine sawflies) is important, since their outbreak occurs 1.5 years earlier than pests with annual generation. In areas with a 2-year development cycle of the Siberian silkworm, mass reproduction of many forest pests with an annual generation, outbreaks of which, generated by the same drought, develop faster, can be perceived as alarms. Such signaling pests include the gypsy moth, ancient, larch and willow moths, larch and pine moths, pine silkworms, larch moths, polyflowers, hawthorn, and in the forest-steppe - locust moths (Siberian moth). Outbreaks of mass reproduction of the gypsy moth and the larch moth do not only occur in tandem. The primary centers of their mass reproduction are formed in similar, and often even in the same larch plantings (Yu. P. Kondakov, 1959).

In plantations affected by ground fires, it is necessary to carry out appropriate methods of supervision over the reproduction of silkworms in the first 3 - 4 years in areas with annual or variable generations, or in the first 6 - 8 years in areas with 2-year generation, even regardless of droughts, since fires can cause local outbreaks that can grow into larger outbreaks during dry periods.

Control measures

Spraying plantings with insecticides in the spring, within 1-2 weeks after the overwintered caterpillars rise into the crowns, or at the end of summer - against young caterpillars.

- a large-sized butterfly with inconspicuous wing colors; the insect belongs to the family of cocoon moths. 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 camouflage themselves on the bark of trees and serves as protection.

Spreading

Widely distributed throughout Russia, its habitat is limited to the Ural, West Siberian, East Siberian and Far Eastern regions. It is in the territory of Siberia and the Far East that the Siberian silkworm has quarantine significance, 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 comes not from the butterfly itself, but from its caterpillars. Siberian silkworm caterpillars hatched from eggs easily acclimatize, are hardy and very voracious.

Life cycle

An adult butterfly lays 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 of eggs laid by one female is up to 800 eggs. The greenish-blue egg is round in shape and measures about 2 mm. One clutch can contain from 10 to 100 eggs.

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

In order to develop into a butterfly, the caterpillar must survive two overwintering periods, feeding vigorously during the spring and summer (May to mid-August). Entomologists distinguish 6-8 instars of the caterpillar, during which it goes through 5-7 molts. The greatest damage to trees is caused by caterpillars that have survived the second winter; it is at this time that they consume 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: ichneumon flies, tahini flies or hedgehog flies, and egg-eating ichneumon flies. Braconids and trichogrammas take a particularly active part in regulating the number of agricultural pests. Trichogramma lay their young (up to four eggs) directly into the silkworm eggs. Tachins are also entomophagous insects, but they lay 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 the caterpillars and adult insects of the Siberian silkworm. Fungal infections also affect the development of insects.

Pest danger

The danger of the species is that the insect can increase the population several hundred times after going through a two-year development cycle. In Siberia and the Far East, millions of hectares of healthy coniferous forest were lost due to the harmful activities of insects. 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 longhorned beetles select weak trees and use them to lay offspring in the subcortical layer, after which the beetle larvae eat the tree from the inside. Thus, the insects that have taken over the baton completely destroy the forest, turning it into dead dead wood, which is not suitable for serious construction work. Renewing forests in ruined areas will take at least a hundred years.

To ensure that the problem with the Siberian silkworm does not grow to global proportions, it is necessary to combat the dangerous pest.

Prevention of spread

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

Phytosanitary restrictions include the following measures:

• Disinfection and debarking of coniferous species before transportation;
• An accompanying certificate confirming processing is required for the cargo.

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

Fighting the Siberian silkworm

Mechanical methods of extermination (collecting caterpillars and pupae, removing infected needles) of the pest turn out to be of little effectiveness, since the pest's foci are usually located in the remote taiga. Aerial photography or a careful visual inspection of the area will help identify dangerous areas. The area 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 massive death of caterpillars and butterflies. For this purpose, insecticide is sprayed from an airplane onto the infected area.

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

There are biological and chemical insecticides against the pest. Among biological agents, lepidocide can be distinguished, which is successfully used to combat 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 the caterpillars, they stop experiencing hunger and die from exhaustion. The drug also affects adults: butterflies cannot tolerate the smell of this drug, so their age decreases, and after it the number of eggs laid decreases.

Siberian silkworm - a threat to the coniferous forest

It is possible to cope with the worst pest of coniferous species only with the help of carefully organized detailed supervision and compliance with all sanitary treatment 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 that require special attention from supervisory organizations:

• Areas that have experienced drought;
• Area affected by fires.

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

Let's talk about Siberian silkworm is a species of butterfly that lives in coniferous forests. It is quite large in size, for example, its wingspan reaches sixty to eighty millimeters in the female, and forty to sixty centimeters in the male. It belongs to the family of cocoon moths. Its caterpillars feed on coniferous trees. She especially prefers trees such as larch, spruce, common 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 white spot. The wings that are located at the back 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, spherical in shape. If you look at them, then on each egg you can see a brown dot, and the color of the eggs themselves is green with blue and turns into gray. There can be thirty, forty or more of them in one clutch, sometimes up to two hundred. The eggs develop over about thirteen days, sometimes up to twenty-two. After this, the caterpillar emerges from mid-August and feeds on needles. She lives, feeds and develops into a more adult individual. In the month of September, towards the end, the caterpillar prepares for wintering. It overwinters under moss and fallen pine needles, being in a state of complete dormancy. 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 in color.

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

The pupae reach a length of twenty-eight to thirty-nine centimeters. The color of the pupa is light, then turns into brown, and over 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 a fairly large area. It is also common in Asia: Kazakhstan, Mongolia and other countries. The difference in temperature does not frighten it much and therefore it is widespread from Siberia to Asia and beyond. This type of silkworm is considered a pest of forest trees. The spread of the Siberian silkworm towards the west is also noted.

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

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 destructive consequences of its invasion for the healthy existence of coniferous forests?

The Siberian silkworm butterfly is inconspicuous at first glance and appears to be absolutely safe. But this is far from true. These pests are increasingly caught in special traps, and scientists have sounded the alarm: the population of this pest is growing rapidly. In fact, the ten-centimeter insect is not so dangerous, especially for coniferous forests, and damage to forest plantations is caused by its caterpillars hatched from eggs. They are able to quickly acclimatize, are quite hardy, and have an excellent appetite.

In the Amur region, the Siberian silkworm was discovered in the Blagoveshchensk region in 2008. Compared to other subjects of the Russian Federation located in Siberia and the Far East, the situation with the Siberian silkworm is quite favorable. However, you should not get your hopes up, because... Even one individual silkworm can create a serious problem.

Periodically, approximately once every 10 years, an outbreak of the Siberian silkworm population occurs, the consequences of which are the destruction of huge areas of valuable coniferous plantations. The use of modern insecticidal pyrethroid and bacterial preparations in recent years has made it possible to partially localize the pest outbreaks 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, destruction of tree stands and changes in forest formations.

Foci of mass reproduction are observed in Russia annually on an area from 4.2 thousand to 6.9 million hectares and cause significant damage to forestry. This is exactly what 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 increase in the popularity of the Siberian silkworm, all coniferous forest plantations, including growing seedlings of coniferous pines and fir trees, died. The remains 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.

Satellite monitoring is used for timely detection of breeding foci.

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

Externally, 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 intersected by three darker stripes. There is a large white spot in the middle of each wing; the hind wings are the same color.

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

Siberian silkworm caterpillars 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 if there is a lack of food, the bark of thin shoots and young cones. In the fall they leave for the second winter. In May-June of the following year, adult caterpillars feed intensively, causing the greatest harm. During this period, they eat 95% of the food needed for full development.

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

Butterflies don't feed. The female lays an average of about 300 eggs, placing them singly or in groups.

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

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

The main danger of an outbreak of the Siberian silkworm is not only that an average of 0.8 million hectares are destroyed annually by the Siberian silkworm, but also that forests destroyed by silkworms are poorly restored. The caterpillars destroy the undergrowth along with the forest stand, and only after a decade is it possible for a small undergrowth of deciduous species to appear. In old foci, conifers appear only 30-40 years after the forest stands dry out, and not everywhere and not always.

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

The quality of the forest stand is deteriorating.

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

During mass reproduction, coniferous trees should be treated with insecticides. The most effective biological drug at present is lepidocide.

And to prevent Siberian silkworms, it is necessary to regularly inspect trees for the presence of pests and carry out preventive treatment with insect repellents.

To avoid the spread of the Siberian silkworm, Rosselkhoznadzor experts recommend introducing a number of phytosanitary restrictions: when exporting coniferous species, 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 the appropriate accompanying certificate, such cargo may be illegal.

If detected, you must contact the Amur branch of the Federal State Budgetary Institution "Trans-Baikal Reference Center of Rosselkhoznadzor" to carry out the necessary processing.

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

N 99-FZ "On plant quarantine", Resolution of the Governor of the Amur Region dated 04/13/2009 N 187 "On the imposition of quarantine on the Siberian silkworm in the Blagoveshchensk region", as well as the order of the Ministry of Agriculture of the Russian Federation dated 03/14/2007 No. 163 " On the organization for issuing phytosanitary certificates and quarantine certificates." Permits are issued based on the conclusion issued by the Amur branch of the Federal State Budgetary Institution "Trans-Baikal Reference Center of Rosselkhoznadzor" on the quarantine phytosanitary state of regulated products.