Home – Home – Jornals – Siberian Journal of Forest Science 2021 number 5

The capsule review of the scientific editor for the thematic issue of the Siberian Journal of Forest Science, 2021, number 5 is done, dedicated to the Siberian silkworm problems.

Commemorative article dedicated to the 90^th anniversary of the outstanding Russian scientist and organizer of science, academician of the Russian Academy of Sciences Alexander Sergeevich Isaev.

The article describes the main stages in the development of biological methods for protecting forests from the caterpillars of the Siberian moth Dendrolimus sibiricus Tschetv. in Russia, from the first half of the 20^th century to the present. It has been shown that the use of bacterial preparations is of the greatest importance in the practice of forest protection; Lepidocide is currently the most widely used biopesticide. Previously, there was a viral preparation as a means of protection, but currently there are no viral preparations approved for use. Information on the development of fungi preparations is given, but it is emphasized that effective and reliable fungi preparations have never been available to combat this pest. A detailed historical analysis of the development of the classical biological control in forest protection from the Siberian moth is given. Cases of successful use of the egg parasitoid Telenomus tetratomus Kieffer and the technology by which this entomophage was used are described. The reasons are discussed that the use of this species has not become an important part of the biological protection system of taiga forests. The authors are convinced that the use of such biological agents of forest protection as entomophages, pathogenic fungi and viruses is possible only in those cases when suitable technologies of application and bio-production will be developed for each of them. Bacterial preparations are widely used in the practice of forest protection from Siberian moth due to the well-developed production technology, and the similarity of the technology of their use with chemical pesticides, while guaranteeing a reliable result.

Models of the population dynamics of forest insects are considered based on the concept of an outbreak as a first order phase transition of the (this sentence is not complete) As objects of the studies, the population of the Siberian silkmoth in Siberia and the Far East, the population of the pine moth in Europe, the population of the gypsy moth in the Urals, and the population of the gray larch leaf worm in the Alps are considered. In this work, models fo same species of forest insects are considered, that make it possible to estimate the critical population densities and, in this regard, to propose algorithms, on the basis of which it is possible to make decisions on the implementation of protective measures. A model of the population dynamics is considered as an analog of a phase transition in physical systems to describe the dynamics of the population. An algorithm for transforming of population dynamics time series is proposed to reduce the level of errors in the course of density counting of pest populations. A state function is proposed as a characteristic of population dynamics, calculated as the reciprocal of the probability of finding a population in a state with a given population density. The functions of the state of populations with modes of outbreaks are characterized by the presence of two local minima and one local maximum - a potential barrier. A method is proposed for calculating the functions of state of populations based on data from time series of population dynamics, characteristics of state functions are described, such as local stable densities, critical and semi-critical density, susceptibility of the state function to changes in population density, and the half-width of the potential barrier. Indicators are introduced - indicators of the risk of outbreaks. Assessments of the risks of outbreaks are given for the studied species of phyllophagous insects.

Regularities of micro and macro-spatial distribution of individuals of Siberian silkworm populations during an outbreak of mass reproduction are considered. When studying the spatial distribution of the Siberian silkworm, a model of the distribution of individuals of the Siberian silkworm among fodder trees on sample plots was considered and the shape of areas damaged by the Siberian silkworm was studied. Additionally, a model of long-term spatial dynamics of insect pest’s population centers is considered. To assess the micro-spatial distribution of individuals on the territory, the spatial dynamics of the distribution of Siberian silkworm caterpillars on trees at different stages of the pest population gradation are considered. To describe the distribution of insects over trees on test plots, a model is proposed - an analogue of the model of phase transitions of the second kind in physical systems. To describe the “movement” of the boundaries of the center of mass reproduction of insect pests, the model of “viscous fingers” is considered and the fractal characteristics of the boundaries of the centers are calculated. By assessing the fractal dimension of the outbreak boundary, it is possible to calculate the ratio of the population density and the time of development of the forage object, and from the fractal dimension of the boundary between the outbreak and the undamaged forest, it is possible to estimate the nature of the further development of the outbreak. Also, based on a single measurement of the structure of the focus boundaries, one can try to estimate the fractal dimension of the focus and the risk of its further development. The considered models were verified according to the observations of various authors. When constructing and verifying the models, we used the data of the counts of the Siberian silkworm population and the population of trees in the foci of its mass reproduction, and remote data on the areas and shape of the foci. Using the proposed models, it is possible to estimate the critical characteristics of the population density and the shape of the foci of mass reproduction of pests at different phases of population gradation based on the data of counts and remote observations.

It is known that weather affects the development of outbreaks of Siberian silkmoth Dendrolimus sibiricus Tschetv. breeding. In this regard, the purpose of these studies was to study the influence of weather factors - temperature and precipitation on the possibility of developing of Siberian silkmoth population outbreaks. For a correct assessment of the influence of climatic factors on the dynamics of the number of forest insects and the development of outbreaks of pests, the concept of necessary and sufficient weather conditions was introduced to facilitate outbreaks of phyllophages. An approach is proposed to assess whether certain weather conditions are necessary or sufficient for the development of outbreaks of the Siberian silkworm in Krasnoyarsk Krai. Selyaninov’s hydrothermal coefficient (HTC) was chosen as an integral indicator of weather conditions: the ratio of the amount of precipitation for a certain period to the average temperature for this period. The Bayesian approach was used to calculate the conditional flare probabilities. For various forests in the territory of Krasnoyarsk Krai in which outbreaks of the Siberian silk moth were observed, analyses were carried out for May, June, July, August, and September in the period from 1980 to 2017. Analysis of the relationship between weather conditions and the development of outbreaks of the Siberian silk moth showed that a necessary condition for the occurrence of an outbreak of this pest in Krasnoyarsk Krai is dry and warm weather in May of the year preceding the onset of the outbreak. However, dry and warm weather in spring - early summer is not a sufficient condition for a future outbreak, and additional indicators are needed to predict the outbreak. Nevertheless, when the weather with HTC < 1 is realized, it is necessary to start carrying out a more detailed monitoring of the state of the pest population. It seems that the proposed calculation method can be used to assess the effect of weather on the development of the population not only for the Siberian silk moth, but also for other species of forest insect pests.

The Siberian silk moth Dendrolimus sibiricus Tschetv. is one of the most dangerous pests of taiga forests. Large-scale outbreaks of the population and the expansion of the pest’s habitat attract scientists to the study of insect sex pheromones. The Siberian silk moths use pheromones to attract mating partners. Pheromone communication is a complex multistage process, including the synthesis of pheromone, the spread of odorous substances in the environment, the perception of the pheromone signal by other individuals, and the behavioral response of individuals receiving the signal. Effective transmission of the pheromone signal is ensured due to the preservation of the chemical composition and conformation of molecules during propagation in the air, as well as their ability to decompose at a certain time under the influence of external factors. The stability and reactivity of molecules is determined by their physicochemical characteristics. Structural and spectral properties of molecules were investigated using methods of computer molecular modeling. Quantum chemical calculations were performed using the density functional theory B3LYP/DFT, which is widely used to study small organic molecules. A detailed analysis of the atomic and electronic structure of molecules in the ground and excited states was carried out, and the absorption spectra of molecules were calculated. The wavelengths and absorption intensity were determined. Based on the data obtained, a conclusion was made about the stability of pheromone molecules to the effects of sunlight, an assessment was made of the possibility of changing the chemical composition and structure of molecules as a result of absorption of ultraviolet radiation. The calculated data obtained were compared with the data on the daily patterns of insects.

To assess the state of plantations in vast areas of boreal forests, modern methods are needed that allow obtaining information quickly with minimal labor costs. The existing assessment methods are either associated with labor-consuming ground-based observations, or they make it possible to measure the damage that has already occurred using remote sensing data (satellite, aeronautical observation methods). Methods for analyzing the state of forest stands in large areas (such as taiga forests in Siberia) based on remote sensing data are proposed. As an indicator of the state of stands, it is proposed to use the susceptibility index of vegetation index during the season (NDVI) to changes in the radiation temperature (LST), obtained from satellite data of the Terra/Aqua system. The index was calculated as the transfer spectral response function in the integral equation between NDVI and LST. The analysis was made for two types fir stands of Krasnoyarsk Region taiga zone - territories that since 2015 were damaged by of the Siberian silkmoth Dendrolimis sibiricus Tschetv. caterpillars and nearest intact areas. It is shown that indicators of stands’ susceptibility to environmental changes on the studied test plots changed significantly 2-3 years before pest population outbreaks and can be taken into account when assessing the risk of outbreaks. This distinguishes proposed indicator from assessments of the vegetation cover state, which register a significant defoliation of forest stands and cannot be used for forecasting.

The article is devoted to the research of natural regeneration of the pine forest, which suffered from outbreak foci of Siberian moths Dendrolimus sibiricus Tschetv. The studies were carried out in far south of Tomsk Oblast in the subzone of the subtaiga on the southern border of closed Siberian pine forest area on West Siberian plain in 2011-2015. The results of the research of the dynamic of the undergrowth condition of the Siberian pine forest with different defoliation level of maternal canopy were presented in the article. To assess vitality of the undergrowth of various species, a reference method was used that is based on comparison of morphological inventory indicators of young plants with pre-selected standard items. It was shown that the vitality and survivability of the undergrowth influence the damage level of the tree stands by the Siberian moths. In completely-eaten stands, dark coniferous undergrowth of preliminary reforestation died and broad-leaved trees took up the major portion in the composition of the undergrowth. In the stands of heavily weakened trees the increase in portion of aspen was determined. Under the canopy of the plantation with weak defoliation, the dramatic changes in species composition of the undergrowth did not take place. Prevalence of dark coniferous species is still being observed but its quantity is not enough for successful reforestation. The changes of lighting did not cause either positive or negative reactions of Siberian pines or fir trees undergrowth to an increase in lighting.

The first note about the outbreaks of the Siberian moth Dendrolimus sibiricus Tschetv. (Lepidoptera, Lasiocampidae) was published 125 years ago. The pest outbreaks of the 1950s and 1960s are poorly documented in Krasnoyarsk Krai. For the first time we provide the details of planning, organizing and implementing large-scale measures to combat the Siberian moth outbreak in the second half of the 1960s. The outbreaks that occurred in the southern taiga forests of the region covered an area of 260 thousand hectares. The maximal insect density reached 7 thousand caterpillars per one fir tree. The outbreak was successfully suppressed thanks to its early prediction, development and implementation of surveillance methods, as well as methods of aerial treatment and assessment of efficiency of protection measures. In 1967-1969, the crews of 45 An-2 aircraft during 2.5 thousand flight hours treated more than 200 thousand hectares of the pest foci with the dichlorodiphenyltrichloroethane (DDT) and hexachlorocyclohexane solution. Over 1,100 people took part in the aeronautical work, including about 250 engineers and technicians. During the 1960s outbreak, the total labor costs for airborne combat with the Siberian moth exceeded 22.000 man-days. To control the Siberian moth, for the first time, high concentration of the insecticide was used, i. e. 20 % oil solution of DDT + hexachlorocyclohexane, with ultra-low consumption rates of working solutions (from 3 to 5 l/ha). The Siberian moth outbreak that occurred on in Krasnoyarsk Territory in the mid-1960s clearly demonstrated high importance of cooperation between scientists and forest protection practitioners. The joint work contributed to the initiation of a specialized institution - the Station (later the Center) of forest protection of the Krasnoyarsk Territory, which leaders in different years were the researchers from the V. N. Sukachev Institute of Forest Sib. Br. Rus. Acad. Sci.

The principles of organization in the forest protection system and the principles of decision-making in the tasks of carrying out protective measures are discussed. The problem of assessing costs and risks in the course of forest protection measures is considered. The functioning of a security service is better understood when viewed as an agent-principal system. In the «agent-principal» system, agency relations are established when one person - the principal or the owner (principal) - transfers certain rights to another person - the agent. In this case, the agent, in accordance with the contract concluded between them, is obliged to act in the interests of the principal in exchange for remuneration. The agent problem, well known in the contract theory of economic systems management, is that if the managing manager is not the owner (principal) of the control structure, then there is a mismatch between the management goals of the principal and the agent. Each of them - both the agent and the principal - has their own interests. The agent has its own interests, and he tends to follow the goals of the principal only to the extent that the contract encourages him to do so. In such a system, there is an uneven distribution of information between the agent and the principal. By analogy with such economic systems, the system of forest protection is considered, where the state or the region is the principal, and the heads of regional structures of the forest protection system have information about the state of the forest ecosystem and the right to make managerial decisions. The features of the functioning of such a system are discussed. The problem of decision-making when carrying out protective measures is considered. The main feature of the decision-making process when protecting a forest from an attack by insects is that there is a lag between the moment a decision is made to switch to protective measures and the moment when protective measures begin. A decision-making model that minimizes the risks of errors is considered. The proposed approach makes it possible to evaluate the efficiency of decision-making in forest protection tasks, depending on the management principles used. The optimal decision on carrying out protective measures will be while minimizing errors of the first and second genera and the risk of damage to the plantation. In the proposed decision-making model, the coefficients for a certain type of pest can be determined from long-term survey data, while as an indicator of the state of the population, it is possible to use not only the values of its density, but also other indicators.