Usually outbreaks of mass reproduction of the Siberian silkworm. The Siberian silkworm is one of the most dangerous insect pests. Give for nuts
Siberian silkworm(Dendrolimus superans sibiricus Tschetv.)
Siberian silkworm (Dendrolimus superans sibiricus Tscetv.) in the Asian part of Russia is one of the most dangerous insect pests coniferous forests, especially in Siberia and Far East. Periodic large-scale outbreaks of mass reproduction of this phytophage 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 annually on an area from 4.2 thousand to 6.9 million hectares (an average of 0.8 million hectares) and cause significant damage to forestry. Therefore, satellite monitoring as part of entomological monitoring of forests is an important element of monitoring the state of forest cover, ensuring, if properly performed, the preservation of the most important ecological functions of forests.
Russia has made a huge contribution to the development and implementation biological methods the fight against foci of mass reproduction of the Siberian silkworm was contributed by Doctor of Biological Sciences, Prof. Talalaev E.V. In the mid-1990s, vast areas were affected by silkworms. forest plantations in Western and Eastern Siberia, as well as in the Far East. In the Krasnoyarsk Territory alone, over the course of four years, the outbreak covered the territories of 15 forestry enterprises; the area of damaged taiga areas amounted to more than 600 thousand hectares. Destroyed a large number of valuable cedar plantations. Over the past 100 years, 9 outbreaks of the pest have been registered in the Krasnoyarsk Territory. As a result, forests covering an area of more than 10 million hectares were damaged. The use of modern insecticidal pyrethroid and bacterial preparations 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.
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 (II-III quality class) stands of forb-green moss forest types with the participation of fir up to six units or more, with a density of 0.3-0.6.
Adult of the Siberian silkworm. Photo: Natalia Kirichenko, Bugwood.org
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, but most often the fertility does not exceed 200-300 eggs.
The eggs are almost spherical in shape, up to 2mm 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.
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 (Fig.).
The first molt occurs after 9-12 days, the second after 3-4. In the first instar, the caterpillars eat only the edges of the needles; in the second instar, they eat the entire needle. At the end of September, the caterpillars burrow into the litter, where they overwinter under moss cover.
At the end of April, the caterpillars climb into the tree crowns and begin to feed, eating whole needles, and if there is a lack of food, the bark of thin shoots and young cones. After about a month, the caterpillars molt for the third time, and again in the second half of July. 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. They molt 5-7 times and accordingly go through 6-8 instars.
Caterpillars feed on the needles of almost all coniferous species. 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. Pupa, 25-45 mm long, brownish-red, then dark brown, almost black. The development of the pupa depends on temperature and lasts about a month. Mass migration of butterflies occurs in the second ten days of July. On the southern slopes of the mountains it occurs earlier, on the northern slopes - later.
The development cycle of the Siberian silkworm usually lasts 2 years. But 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. The flight of butterflies begins in the second half of July and lasts about a month. Butterflies don't feed. The wingspan of females ranges from 6 to 10 cm; males - 4-5 cm. Unlike females, males have feathery antennae. The female lays an average of about 300 eggs, placing them one at a time or in groups on the needles in the upper part of the crown. In the second half of August, caterpillars of the first instar emerge from the eggs, feed on green needles, and in the second or third instar, at the end of September, they leave for the winter. Caterpillars overwinter in the litter under a cover of moss and a layer of fallen pine needles. The rise in the crown is observed in May after the snow melts. The caterpillars feed until next autumn and leave for the second wintering at the fifth or sixth age. In the spring they rise again into the crowns and after active nutrition in June they weave a dense gray cocoon, inside which they then pupate. The development of the silkworm in the pupa lasts 3-4 weeks.
In the dark coniferous taiga, silkworm outbreaks form after several years of hot, dry weather in the summer. In this case, the caterpillars go to winter later, in the third or fourth instar, and turn into butterflies the following summer, switching to a one-year development cycle. Accelerating the development of caterpillars is a condition for the formation of Siberian silkworm foci.
A section of coniferous forest after defoliation by the Siberian silkworm. (Photo by D.L. Grodnitsky).
A forest area defoliated by the Siberian silkworm (photo: http://molbiol.ru)
The count of wintering caterpillars in the litter is carried out in October or early May. The number of caterpillars in the crown is determined by the method of staking on fabric canopies in early June and late August.
The age of the caterpillars is determined according to the table by measuring the width of the head.
It should be borne in mind that in the conditions of Northern Eurasia, 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.
The main reason for the lack of natural regeneration in silkworms is the drastic ecological transformation of plant communities. During the mass reproduction of silkworms, up to 30 t/ha of eaten fragments of needles, excrement and corpses of caterpillars enter the litter and soil within 3-4 weeks. Literally within one season, all the needles in the plantation are processed by the caterpillars and enter the soil. This litter contains a significant amount organic matter- favorable food for soil bacteria and fungi, the activity of which is significantly intensified after the mass reproduction of silkworms.
This is also facilitated by an increase in soil temperature and humidity, since neither sunlight, and precipitation is no longer retained by tree crowns. In fact, the mass reproduction of silkworms contributes to a more intense flow of the biological cycle as a result of the rapid release of significant amounts of matter and energy contained in the forest floor.
The soil in silkworms becomes more fertile. Light-loving grass cover and undergrowth rapidly develop on it, intensive turfing and often waterlogging occurs. As a result, heavily disturbed plantations are replaced by non-forest ecosystems. Therefore, the restoration of plantings close to the original ones is delayed indefinitely, but not less than 200 years (Soldatov et al., 2000).
Outbreaks of mass reproduction of the Siberian silkworm in the forests of the Ural Federal District
In general, despite the large number of works on the ecology of the Siberian silkworm in the 50-60s, many features of the ecology of the Trans-Ural population under conditions of global anthropogenic impact remain unstudied.
Outbreaks of mass reproduction of the Siberian silkworm in larch forests The Cis-Urals have been observed since 1900 [Khanislamov, Yafaeva, 1962]. In the dark coniferous lowland forests of the Trans-Urals in the Sverdlovsk and Tyumen regions, the previous outbreak was observed in 1955-1957, and the next one in 1988-1992. The first outbreak in the forests of the Sverdlovsk region was discovered in 1955 on the territory of the Tavdinsky and Turinsky forestry enterprises. The total area of the outbreaks was 21,000 hectares and 1,600 hectares, respectively. On the territory of the Tavdinsky forestry enterprise, large outbreaks formed earlier. It is noteworthy that these forestry enterprises have been the site of intensive timber harvesting for many decades. Therefore, coniferous forests have undergone anthropogenic transformation and currently have an admixture of secondary birch forest with pine, spruce and fir in the undergrowth. It should be noted that a new outbreak (1988-1992) in the Sverdlovsk region was registered in other forestry enterprises. It was formed to the greatest extent in the forests of the Taborinsky district. The total area of the outbreaks was 862 hectares; individual outbreaks were also observed during aerial surveillance in the Garinsky district.
Research has shown that in 50% of the areas affected by outbreaks in 1988-1992, the main forest-forming species is birch with fir and spruce as part of the undergrowth (Koltunov, 1996, Koltunov et al., 1997). Fir undergrowth is strongly defoliated by the Siberian silkworm and mostly shrunk. As a result, significant damage was caused to the development of coniferous farming in these forestry enterprises. The primary centers of mass reproduction of the Siberian silkworm arose in 1988 in stands with fir undergrowth. In 1993, the outbreak completely died out. On the territory of KHMAO-YUGRA, the outbreak of mass reproduction died out in 1992. In some areas, spruce was defoliated by the Siberian silkworm, as a result of which it also quickly dried out. As surveys in the foci of this phytophage during the outbreak have shown, the development of the Trans-Ural population occurs mainly in a two-year cycle. In general, studies have shown that the topography of the broad silkworm foci in the coniferous forests of the Sverdlovsk region coincides with forest areas disturbed by anthropogenic impact.
On the territory of Khanty-Mansiysk Autonomous Okrug an outbreak of mass reproduction of the Siberian silkworm was discovered in the territories of Mezhdurechensky, Uraysky, Tobolsky, Vagaysky and Dubrovinsky forestry enterprises. The total area of the outbreaks was 53,000 hectares. We carried out the most detailed studies in the foci of mass reproduction of the Siberian silkworm in the Mezhdurechensky forestry enterprise.
Over the past 20 years, the most intensive industrial logging has occurred on the territory of the Yuzhno-Kondinskoe private plot. As the results showed, the spatial structure of the foci of mass reproduction of the Siberian silkworm in this forestry enterprise clearly does not coincide with the forests subjected to the most intense anthropogenic impact (primarily deforestation). The largest foci (in the western part of the forestry enterprise) are completely unaffected by anthropogenic impact. There was no logging in the forests before the outbreak. We also did not find any other types of anthropogenic impact. Analysis of forest taxation parameters of tree stands in this group of outbreaks showed that these forests have the usual productivity for this type of forest growth conditions and are not weakened. At the same time, near other, smaller sources, clearings and, in some cases, fires are observed. Some of the areas with severe defoliation of tree stand crowns were previously logging.
As the results showed, anthropogenic impact in the dark coniferous lowland forests of the Trans-Ural region is not a key factor in the formation of foci of mass reproduction of the Siberian silkworm, although its contribution is undoubted. Under conditions of moderate anthropogenic impact, the main factor in organizing the spatial structure of outbreaks is forest conditions in ecotopes and microrelief features. Thus, the largest foci are adjacent to river beds and places with microhighs, which was known earlier [Kolomiets, 1960,1962; Ivliev, 1960]. Especially important fact is that the forests in the hotspot areas were not noticeably weakened under the influence of anthropogenic factors. The level of anthropogenic transformation of these forests was extremely insignificant, no higher than stage 1 in some ecotopes (5-10% of forests). As shown by geobotanical analysis of the herbaceous layer, the grass cover in these forests has not changed.
Thus, these forests are most affected only by their proximity to clearings (changes in light and wind conditions) and, to a lesser extent, by logging carried out several decades ago in some of them.
Analysis of the radial growth of trees in the foci and beyond their boundaries confirms our conclusion about the preservation of the stability of forests as a whole that have undergone defoliation. We associate the reduced radial growth of trees in the foci with the adaptive response of forest stands to forest vegetation | conditions, but not with their weakening, since we did not find these differences in last years, and for 50 years or more.
A characteristic feature of the dynamics of defoliation of tree stands during the outbreak in the lowland forests of the Trans-Urals was a clear preference for defoliation of fir in the undergrowth at the beginning of the outbreak, then of fir in the main layer, and later of spruce and cedar. The pine was defoliated very weakly. Therefore, no outbreaks formed in pure pine forests. A study of the trans-Ural population of Siberian silkworms in outbreaks showed that in the eruptive phase and before the outbreak subsided, the adult birth rate was very low and ranged from 2 to 30%, averaging 9.16%.
Most of the pupal population dies. The most significant percentage of the population dies from infectious diseases (bacteriosis and granulosa virus). Death from these causes ranges from 29.0 to 64.0%, with an average of 47.7%. Bacterial infections constituted the main percentage of causes of death from this group of diseases. Viral infections were significantly less common. It should also be noted that microscopic analysis of dead caterpillars in outbreaks both in Sverdlovsk and Khanty-Mansi Autonomous Okrug convincingly showed that the attenuation of outbreaks was not accompanied by a viral epizootic (granulosa virus).
Our results are in good agreement with the data of other researchers on other populations of the Siberian silkworm [Khanislamov, Yafaeva, 1958; Boldaruev, 1960,1968; Ivliev, 1960; Rozhkov, 1965].
During the period of attenuation of the outbreak of mass reproduction of the Siberian silkworm in the forests of the Khanty-Mansiysk Autonomous Okrug, up to 30 caterpillars per 1 m 2 were found in the litter, dying from infectious diseases.
As the results showed interesting feature of forest stands that dried out after defoliation by the Siberian silkworm in the lowland dark coniferous forests of the Khanty-Mansi Autonomous Okrug, there was an almost complete absence of colonization by xylophagous insects within 1-2 years after drying out, although in forests undamaged by the Siberian silkworm, colonization of drying stands and individual trees by xylophages was observed .
It should be noted that the supply of xylophages in the outbreak areas is sufficient. In addition, at shift sites and in stock warehouses in the Yuzhno-Kondinsky private farm, the canes left untreated are quickly colonized by xylophagous insects. We associate the slowdown in the colonization of shrunken forest stands by xylophages after their defoliation by the Siberian silkworm to a greater extent with high humidity wood This, in our opinion, was due to the active transport of water by the root system of trees after defoliation of the crowns against the background of the cessation of transpiration due to the absence of needles.
Research in the centers of mass reproduction of the Siberian silkworm in the Trans-Urals showed: the last outbreak of this phytophage in the dark coniferous forests of the lowland Trans-Urals was observed 33 years ago. It can be assumed that the cyclical outbreaks of this phytophage on the western border of the range are closely related to the periodicity of the most severe droughts in 1955 and 1986. The most severe drought (in 1955) was accompanied by a larger area of foci of this phytophage in the Trans-Urals.
Previously, there were no outbreaks of Siberian silkworm in the Kondinsky forestry enterprise. Dendrochronological analysis of fir and spruce cores (over the last 100-120 years), carried out by us, showed that forest stands both in the outbreak and beyond its borders had not previously been subject to noticeable defoliation. Based on our results, we can assume that the Siberian silkworm is gradually penetrating to the north and outbreaks of mass reproduction that have not previously been observed there occur in these habitats. This is probably due to gradual climate warming.
The relationship between the spatial structure of foci and anthropogenic impact on forest biogeocenoses is not convincingly traced. Outbreaks were identified both in forest areas where active logging took place, and in forests completely unaffected by logging, which are significantly removed from roads, winter roads and villages.
Based on the results obtained, it was established that under the conditions of anthropogenic transformation of dark coniferous forests of the Trans-Ural region, the largest foci of the Siberian silkworm can arise both in completely undisturbed forests and in forests exposed to anthropogenic factors.
A comparative analysis of the spatiotemporal structure of the foci during the last two outbreaks shows that the foci of mass reproduction each time are formed in different ecotopes and spatially do not coincide at all. As the research results showed, the first outbreaks in each of the surveyed forestry enterprises arose in 1988 simultaneously with other outbreaks in the more southern regions of the Tyumen region. This excludes the possibility their origin through migration from the southern part of their range. It is likely that the population was in a depression phase in the northern part of the range of this population.
At the western border of the range of this phytophage, outbreaks are fast-moving. This is well explained by the narrow time interval of the climatic optimum during the drought period. Considering this, as well as the presence of a two-year cycle in Siberian silkworm caterpillars, this gives good prospects for reducing the economic damage from outbreaks through the use of active measures in the period immediately before the eruptive phase of the outbreak. Maintaining a high outbreak potential is only possible during this narrow period of drought. Therefore, treating lesions during this period will eliminate the likelihood of the formation of large repeated steps.
As shown by the results of a comparative analysis of forest taxation parameters of 50 trial plots established in the foci of mass reproduction of the Trans-Ural population of the Siberian silkworm in the Taborinsk forestry enterprise of the Sverdlovsk region, the foci were formed in forest stands with different completeness: from 0.5 to 1.0, on average - 0. 8 (Table 3.1,3.2). Correlation analysis showed that the areas of lesions were positively correlated with the quality class (R=0.541) (with worse growth conditions), average height (R=0.54) and negatively correlated with fullness (R=-0.54).
However, it is noteworthy that out of 50 sample plots, only 36% of the plots with a density lower than 0.8 formed foci of mass reproduction of the Trans-Ural population of the Siberian silkworm, while in the vast majority of the trial plots the density was 0.8 and higher. The average level of defoliation of lower-density forest stands is, on average, 54.5%, while that of high-density forest stands (with a density of 0.8 or more) is 70.1%, but the differences were statistically insignificant. This probably indicates that the level of defoliation is influenced by a complex of other factors that are common to the group of forest stands. The contribution of this group of factors to the level of entomoresistance of forest stands was significantly higher than the influence of the completeness of forest stands.
Research has shown that this factor is the soil-edaphic conditions in ecotopes. Thus, all the forest stands on the test plots, which were located on ridges, in drier habitats, were defoliated the most severely, compared to the forest stands on the flat parts of the relief, or microdepressions. Correlation analysis of the degree of defoliation with other forest taxation parameters also did not reveal a statistically significant relationship with the quality class (r = 0.285). However, the average level of defoliation of the lowest quality forest stands (with quality class: 4-5 A) was 45.55%, while in the highest quality stands it was 68.33%. The differences are statistically significant (at P = 0.01). The absence of a reliable linear correlation was also probably due to the strong dominance of the factor of soil-edaphic conditions. This is accompanied by severe defoliation of forest stands, which vary significantly in quality class. It is also impossible to exclude the possible influence of the factor of local migration of caterpillars from completely defoliated high-quality stands to nearby low-quality stands. Although it should be noted that we recorded caterpillars in the crown in both groups of forest stands. Consequently, local migration in any case was not the main cause of severe defoliation of low-grade forest stands.
Analysis of the results shows that in the conditions of lowland dark coniferous forests of the Sverdlovsk region. there is a certain tendency towards the predominant formation of foci with the most severe defoliation of crowns in forest stands with more high class bonitet. But there is also no noticeable avoidance of low quality forest stands. Foci with varying degrees of crown defoliation occur in forest stands with different quality classes. But the lowest entomoresistance and severe defoliation are characteristic of plantings with the highest quality class. Considering the close relationship of the degree of defoliation with the level of entomoresistance of tree stands at the same initial population density, it can be assumed that in these forest conditions, as a result of exposure to an abiotic stress factor (drought), the entomoresistance of forest stands with a higher quality class decreases more than that of low quality forest stands, which is accompanied by higher crown defoliation high quality forest stands.
Analysis of the characteristics of the composition of forest stands in the foci of mass reproduction of the Siberian silkworm in the Sverdlovsk region made it possible to identify two main types of strategy for the formation of foci in relation to the composition of the forest stands.
1 type of strategy. Outbreaks occur in the main layer of the forest. These tree stands are most often located on the manifold elevated parts relief in drier forest types. Foci with the most significant defoliation of forest stands are formed in spruce-fir and fir-spruce forest stands with an admixture of birch (6P2E2B, 5E2P2B). The undergrowth contains fir, which is the first to undergo severe defoliation. In foci of this type, severe defoliation is always observed. The lesions are usually of a concentrated type with a well-defined border. Surveys in the outbreaks showed that under these conditions, optimal for the outbreak, the predominant composition of rocks is not critical and can vary within fairly wide limits. However, in forests with a predominance of fir in the main layer and undergrowth, the formation of foci with severe defoliation is most likely. It can be assumed that under optimal soil-edaphic conditions general level The drop in entomoresistance of both fir and spruce is higher than the level of differences in entomoresistance between these species in less optimal habitats. According to the composition of the forest stand in these centers, there were no plantations with a predominance of fir at all, but there was a spruce forest with fir and a birch forest with fir undergrowth.
It should be noted that in foci of this type in the Sverdlovsk region there is usually a rapid colonization of dried out stands by xylophagous insects, while in the foci of the Siberian silkworm in the forests of the Khanty-Mansiysk Autonomous Okrug, as mentioned above, the colonization of dead stands by xylophages almost did not occur.
2 type of strategy. Outbreaks occur not in the main forest type, but in the undergrowth. This is typical for forest areas that have been deforested. In this type of forest, outbreaks occur regardless of the species composition of the main layer. This is due to the fact that in many types of forests that have been heavily deforested, there is abundant fir regrowth, which is completely defoliated and dries out. Often the main layer in these types of tree stands is birch, less often pine and other species. Consequently, these forest types are intermediate in the dynamics of succession, when the change of species occurs most often through birch [Kolesnikov, 1961, 1973].
As studies have shown in these types of forests, foci are formed under a wider range of forest vegetation and soil-edaphic conditions. Foci of this type are often found not on elevated, but on flat elements of the relief, but not excessively moist.
In areas with severe defoliation in the forests of the Sverdlovsk region. Aspen is very rarely found in the main layer, since it is an indicator of moist habitats. However, in some areas with severe defoliation it is still found in small quantities. Usually these are foci formed in the flat part of the relief, with individual depressions. As is known, such tree stands begin to be damaged by the Siberian silkworm after a long drought, which reduces soil moisture (Kolomiets, 1958, 1962).
The last outbreak of mass reproduction of the Siberian silkworm occurred in 1999 and continued until 2007 (Fig. 3.3). This was the largest outbreak in Russia over the past 30 years.
The main area consisted of foci of mass reproduction in Siberia and the Far East. In the Trans-Urals, on the contrary, it was very weak. In the forests of the Chelyabinsk region. outbreak areas in 2006 and 2007 amounted to 116 and 115 hectares, respectively, in the forests of the Tyumen region. in 2005, their total area was 200 hectares; in the next 2 years they were not recorded. In the forests of the Sverdlovsk region. she was absent.
For the first time, we conducted research into the development of outbreaks of mass reproduction in the forests of the Sverdlovsk region. and Khanty-Mansiysk Autonomous Okrug (KhMAO-YUGRA).
In general, the results showed a very close similarity in the forest conditions of the preferred ecotopes of the Trans-Ural and West Siberian populations of the Siberian silkworm. This is due to the close similarity of habitat conditions of these populations in swampy lowland dark coniferous forests.
It has been established that, under conditions of anthropogenic transformation of dark coniferous forests of the Trans-Ural region, the Siberian silkworm can form large foci both in forests disturbed by anthropogenic factors and in completely undisturbed forests. Research has shown that a moderate level of anthropogenic transformation of lowland dark coniferous forests in the Trans-Ural region is not the dominant factor in the occurrence of outbreaks. The rank of this factor is approximately similar to other preference factors natural character, the main of which is microrelief and relatively dry habitats.
In the western part of the Siberian silkworm's range, outbreaks are fast-moving. Mostly concentrated foci appear. The nature of the spatial structure of the primary foci suggests that they arose through non-migration and the Siberian silkworm is present in the area of outbreaks and during depression periods. The formation of foci with severe defoliation is observed in forests with a wide range of density and quality classes in the Khanty-Mansi Autonomous Okrug-Yugra - in fir-spruce forests, in the Sverdlovsk region - in derivative birch forests with fir undergrowth and spruce-fir forests.
Dendrochronological analysis of fir and spruce cores (over the last 100-120 years), carried out by us, showed that forest stands both in the outbreak and beyond its borders had not previously been subject to noticeable defoliation. Consequently, previously there were no outbreaks of mass reproduction of the Siberian silkworm in the Kondinsky forestry enterprise of the Khanty-Mansi Autonomous Okrug. Based on our results, we can assume that the Siberian silkworm is gradually penetrating to the north through migration and outbreaks of mass reproduction that have not previously been observed there occur in these habitats. This is probably due to gradual climate warming.
It has been established that the reduced average annual radial growth of spruce and fir in the centers of mass reproduction of the Siberian silkworm is not a consequence of the weakening of forests in recent years, but represents the norm of reaction to relatively dry growth conditions on ridges and microelevations of the relief, and differences in radial growth persist for many decades .
Despite the obvious increase in the scale and level of anthropogenic impact on the lowland dark coniferous forests of the Trans-Urals and Khanty-Mansi Autonomous Okrug-Yugra, the frequency of outbreaks of mass reproduction of the Siberian silkworm has not changed.
The Siberian silkworm in the Trans-Urals and Western part of Western Siberia is still very dangerous pest, causing significant environmental and economic damage to the forestry of the region. Therefore, we consider it necessary to strengthen monitoring of the Trans-Ural population of the Siberian silkworm.
It is quite obvious that the basis for successful control of the Siberian silkworm is periodic monitoring of the number of this phytophage in reservations. Due to the fact that the occurrence of outbreaks of mass reproduction of the Siberian silkworm is closely synchronized with spring-summer droughts, surveillance during this period needs to be significantly strengthened.
It is necessary to analyze the condition and size of the population in other areas of the forest.
Control measures should be planned for the period of the outbreak of mass reproduction, when more than 30% defoliation of fir and spruce, cedar pine, or severe (70%) defoliation of larch is predicted.
As a rule, forests are sprayed with insecticides by air. The most promising biological drug to date is lepidocide.
Siberian silkworm cedar silkworm (Dendrolimus sibiricus), a butterfly of the cocoon moth family, a dangerous pest of coniferous forests. Wingspan up to 90 mm, color gray. Distributed by N. sh. from the shores Pacific Ocean to E. to Southern Urals to the west and from Yakutia to the north Northern China in the south. Damages larch, fir, cedar, rarely spruce, pine. The first butterflies appear at the end of June, the mass flight begins, as a rule, in mid-July and ends in the 1st half of August. S. sh. has a two-year or one-year generation. With a two-year generation, the number of caterpillar ages is 7-8, with a one-year generation - 5-6. The bulk of caterpillars overwinter on the forest floor in the 3rd instar (in larch plantations, more often in the 2nd instar). After thawing snow cover They feed on pine needles, eating them whole. Sometimes buds and even young cones are damaged. Eating needles is one of the reasons for the mass reproduction of stem pests (especially longhorned beetles), which damage plantings and lead to their death. Regulates the number of S. sh. its common natural enemy is the telenomus ichneumon. Mass death of caterpillars of S. sh. usually occurs as a result of epizootics caused by bacteria. Control measures: spraying foci of S. sh. during the development of younger caterpillars with insecticides from airplanes. See also Art. Forest pests. Lit.: Forest entomology, M., 1965. N. N. Khromtsov.
Big Soviet encyclopedia. - M.: Soviet Encyclopedia. 1969-1978 .
See what "Siberian silkworm" is in other dictionaries:
Butterfly of the cocoon moth family; pest of coniferous trees in Siberia and the Far East. The wings are gray. The caterpillars feed on needles, buds, young cones... Big Encyclopedic Dictionary
SIBERIAN SILKWORTH, a butterfly of the cocoon moth family; pest of coniferous trees in Siberia and the Far East. The wings are gray. The caterpillars feed on needles, buds, young cones... encyclopedic Dictionary
SILKWORTH, huh, husband. 1. A butterfly, a caterpillar in a swarm weaves cocoons that are used to make silk (in 1 value). Mulberry sh. 2. Butterfly, caterpillar and swarm is a forest pest. Sibirsky highway Sosnovy highway Dictionary Ozhegova. S.I. Ozhegov, N.Yu. Shvedova... ... Ozhegov's Explanatory Dictionary
Cedar silkworm (Dendrolimus sibiricus), butterfly of the family. cocoon worms. Wingspan up to 90 mm. Butterflies and caterpillars are similar to those of the pine cocoon moth. In Siberia, in the D. East, in the North. Mongolia, North China, Korea, Japan. Mass flight in the 2nd... Biological encyclopedic dictionary
A; m. 1. A butterfly whose caterpillar weaves cocoons that are used to make silk (1 digit). Mulberry sh. 2. A butterfly whose caterpillar is a dangerous pest of tree plantations. Unpaired sh. Kedrovy sh. Sibirsky sh… encyclopedic Dictionary
silkworm- A; m. 1) a butterfly whose caterpillar weaves cocoons that are used to make silk 1) Mulberry silkworm/d. 2) A butterfly whose caterpillar is a dangerous pest of tree plantations. Gypsy moth/d. Cedar silkworm/d. Siberian silkworm/d... Dictionary of many expressions
Morphology. Older caterpillars are very large, reaching 11 cm in length, usually black or black-silver with a wide silver stripe along the back and a yellowish stripe on the sides. Behind the head there are two bands of blue, burning hairs, clearly visible in the disturbed caterpillar. The number of instars and the size of the head capsule vary depending on the duration of the caterpillar phase, which can take one, two or three calendar years. Typically, male caterpillars have 5-8 instars, female caterpillars - from 6 to 9 instars.
The color of butterflies is highly variable, from dark brown to light yellow, almost white. Light gray and dark brown coloration with dark, almost black bands and blurry light spots along the edges on the forewings are typical. The hind wings are usually solid brown. The wingspan of males varies from 40 to 83 mm, females - from 60 to 104 mm.
The eggs are oval, yellowish-brown, forming loose clutches or chains on the needles or branches of food plants. The pupa is in a dense cocoon impregnated with blue burning hairs; placed on branches, less often - on the trunk.
Fodder species. The Siberian silkworm feeds on almost all species of the Pine family. Prefers Siberian fir, Siberian larch and Siberian cedar. The white-striped silkworm prefers Sakhalin fir, Ayan spruce and Kuril larch. On Japanese islands Silkworms damage several types of fir and Korean pine.
Life cycle. The Siberian silkworm has a typical two-year development cycle, taking three calendar years. Butterflies fly and lay eggs in the last third of June - the first half of July. Average fertility is about 300 eggs. The egg stage lasts 17-19 days. The caterpillar overwinters twice: in the second-third instar and in the fifth-seventh instar. They overwinter under the litter, curled up in a ring. Maximum damage is caused to trees by caterpillars feeding in the spring of the third calendar year. They pupate in late May - early June in the crown. The pupal stage takes about three weeks.
The onset of outbreaks of mass reproduction of the Siberian silkworm is usually associated with the transition of part of the population to a one-year development cycle (taking two calendar years). As a result, butterflies of both generations appear simultaneously, which contributes to a significant increase in population density. At the peak of their numbers, silkworm caterpillars are affected by viral, bacterial and fungal diseases. The decline in numbers is also contributed to by about 40 species of insect parasites of eggs (Telenomus tetratomus Thoms., Ooencyrtus pinicola Mats.), caterpillars (Rogas dendrolimi Mats., etc.) and pupae (Masicera sphingivora R.D., etc.).
Harmfulness assessment. The Siberian silkworm is the main pest of coniferous forests in Asian Russia. Outbreaks of its mass reproduction are especially destructive in the dark coniferous taiga dominated by fir and cedar. Over the last 100 years alone, 9 outbreaks of the pest have been recorded in the Krasnoyarsk Territory. As a result, forests covering an area of more than 10 million hectares were damaged. The last outbreak of mass reproduction ended here in 1996. More than 140 thousand hectares of forest perished, and about 50 million cubic meters of wood were lost. Five years later, thanks to the attack on weakened trees by a large black longhorned beetle, the area of shrunken forests doubled.
List A2 pest. Belongs to the cocoon moth family Dendrolimus sibiricus. For EU countries also in the A2 list. Damages coniferous species, especially larch, fir, pine, but can also damage hemlock. First of all, fir and larch. Larch is the most resistant, but fir, on the contrary, suffers the most. It is quite widespread throughout the Russian Federation; it was included in the quarantine list because of other countries. An indigenous species of Siberia, the Far East, and the Urals. In addition, it is found in Kazakhstan, Mongolia, China and Korea. Quite a large butterfly, does not feed. The wingspan reaches 10 cm in females, 4-6 in males. The color of the wings varies greatly: from light yellow-brown to almost brown. Males are usually darker colored. The antennae are feathery. The caterpillars are also quite large; the latest instars can reach 8-10 cm in length. The pupa is dark brown or black; it spins a gray-brown cocoon, which is either in the branches or in the grass. Mass migration of the Siberian silkworm has been observed since mid-July and continues intensively for 30-40 days. After mating, females can fly up to several kilometers. They prefer elevated and less humid places and choose trees. There they lay eggs on needles, mainly in the lower part. If there is a breeding outbreak, eggs can be laid almost anywhere. Both near fallen trunks and in the litter. Fertility is maximum up to 800 eggs, but usually 200-300 eggs. The caterpillars hatch quite quickly and begin hatching in late July-early August. In hungry years, dry needles and young twigs can also be damaged. The generation of this species is 2-3 years, but the duration of development varies. Typically - 2 years; at the 2-3 instar stage, the larva overwinters. In the spring they climb trees again and again feed on pine needles. The detection method is the method of near trees. During outbreaks of mass reproduction, silkworms are easily detected from the air. In addition, a pheromone has been synthesized, which is used in traps. The range of action of one trap is at least 2 km. If the forest is inspected for lumber, eggs and cocoons can be found. Distribution - independently constantly expanding its range to the west and north. On their own, butterflies can fly several kilometers, and with the wind they can fly up to 15 kilometer in a year. Caterpillars can independently crawl 3 km per season. The range will increase by 12 km over the year. This species is often distributed during the trade of transport materials and vehicles that transport it. Often in unbarked logs, wood and bedding seedlings. Stage - egg, caterpillar or cocoon. Severely affects the forests of Siberia and Alstok. Phytosanitary measures: when outbreaks of the Siberian silkworm are identified, measures are taken to localize this outbreak. In the areas where it was detected there is a quarantine phytosanitary regime. Accordingly, a thorough search is carried out from the wounded areas. Sanitary restrictions are introduced in the quarantine phytosanitary zone. All year round Coniferous species must be debarked from May to September. If it is impossible to get through, fumigation. Planting material from bonai to fir trees is prohibited for export from May to September.
Japanese beetle. Elastic moustache. distributed in the eastern part of North America and on Sakhalin Island. Homeland - Southeast Asia, China, Korea and Japan. From there it penetrated into the USA and Canada. Recorded in India, Morocco, and on one island of Portugal. In the Russian Federation it is stable on the island of Kunashir. If it penetrates into the Asian part of the country, it will be able to capture significant territories and the northern borders will pass through St. Petersburg, the Urals, Novosibirsk and Khabarovsk. Polyphage, damages about 300 species of fruit and berry, field, vegetable, ornamental and deciduous plants. The beetle is 7-10 mm, the pronotum is bright green with a metallic sheen, and the elytra are brown with a copper sheen. The larva is S-shaped, up to 2.5 cm long at the last instar. The larva of 2-3 instars overwinters in the soil. The larvae feed on roots. They pupate in mid-summer. The beetles roughly load the leaves and can gnaw flowers and fruits down to the pit. Fruit crops are severely affected. The larvae are no less seriously harmful in field and vegetable crops. Plants are weakened, and plant loss in the form of bald patches is observed. The beetle flies well, spreading over several kilometers, and the larvae spread into plant material. To identify them, the green parts of the plant, cut plants and bouquets from the distribution areas are inspected from June 15 to September 30. If there are fresh food products from Asian countries, they are also inspected. They are treated with insecticides, applied to the soil - systemically, in granules.
Nematode
Colombian potato root-knot nematode.
Major economically important pest in the United States. It was first discovered on the roots and tubers of potatoes in the vicinity of Quincy. There are also reports of detection in Europe, the Netherlands, Jabelgia, Germany, and Portugal. In 1988 it was included in the EPZ list. In Russia - the object of external quarantine. Morphology: Females are spherical to pear-shaped, with a convexity at the posterior end. They are immobile and have a silvery-white color. The body of males is thin, worm-shaped. The eggs have transparent walls.
IN temperate latitudes The cycle is approximately 3-4 weeks. Soil temperature is less important for this species. Slow reproduction occurs even at temperatures of 10 degrees Celsius. Optimal conditions- 15-20 degrees. Early infection greatly affects the quality of potatoes. No more than 10% lesion for sale. Characteristic feature is that eggs are formed on the surface. Preserved in the form of eggs. The typical plant is kratophel, but it can also grow on grains, root crops, legumes, etc. Symptoms are only visible when the infection is severe. Leaves may show chlorotic coloration. Carefully inspect produce from countries with reported cases. The fight is destruction, there are very few resistant varieties and they are not on potatoes.
The coniferous forest is in serious danger, its future is in jeopardy if a short time no effective measures will be taken to combat the worst pest of conifers– Siberian silkworm (Dendrolimus superans). More and more of it began to be found in the coniferous forests of Russia. How dangerous is the Siberian silkworm, and what are the 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.
An adult Siberian silkworm lays its eggs on the branches of coniferous trees. Hatching, the larva immediately begins to eat, moving from the lower crown to the very top, leaving behind only eaten branches. In October, the Siberian silkworm larva goes to winter, and in the spring of next year the third instar larva also continues to feed throughout the warm season. Siberian silkworm caterpillars eat almost all coniferous tree species. After the fifth instar, the more voracious larva again leaves for the winter, after which a butterfly appears and actively begins to lay eggs. In just one season, a female can lay about 800 eggs.
The Siberian silkworm is dangerous because it can cause massive outbreaks reproduction, which will ultimately lead to global destruction million hectares of coniferous forests. This is exactly what has already happened in the Far East and Siberia. Coniferous forest in these areas 
simply amazes with its destruction and mass death. In these places, after the global 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.
To avoid the spread of the Siberian silkworm, Rosselkhoznadzor specialists 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 along coniferous forests 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 you find a Siberian silkworm on the coniferous trees of your site, you must immediately organize measures to combat this pest. Natural enemies pine silkworm- this is a cuckoo, an ichneumon fly and fungal infections.
In case of mass reproduction, it should be treated coniferous trees 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.