The Siberian moth, Dendrolimus sibiricus Tschetv., 1908 (Lepidoptera: Lasiocampidae) is a conifer pest that causes unprecedented forest mortality in Northern Asia, leading to enormous ecological and economic losses. This is the first study summarizing data on the parasitoid diversity and parasitism of this pest over the last 118 years (1905–2022). Based on 860 specimens of freshly reared and archival parasitoids, 16 species from two orders (Hymenoptera and Diptera) were identified morphologically and/or with the use of DNA barcoding. For all of them, data on distribution and hosts and images of parasitoid adults are provided. Among them, the braconid species, Meteorus versicolor (Wesmael, 1835), was documented as a parasitoid of D. sibiricus for the first time. The eastern Palaearctic form, Aleiodes esenbeckii (Hartig, 1838) dendrolimi (Matsumura, 1926), status nov., was resurrected from synonymy as a valid subspecies, and a key for its differentiation from the western Palaearctic subspecies Aleiodes esenbeckii ssp. esenbecki is provided. DNA barcodes of 11 parasitoid species from Siberia, i.e., nine hymenopterans and two dipterans, represented novel records and can be used for accurate molecular genetic identification of species. An exhaustive checklist of parasitoids accounting for 93 species associated with D. sibirisus in northern Asia was compiled. Finally, the literature and original data on parasitism in D. sibiricus populations for the last 83 years (1940–2022) were analysed taking into account the pest population dynamics (i.e., growth, outbreak, decline, and depression phases). A gradual time-lagged increase in egg and pupal parasitism in D. sibiricus populations was detected, with a peak in the pest decline phase. According to long-term observations, the following species are able to cause significant mortality of D. sibiricus in Northern Asia: the hymenopteran egg parasitoids Telenomus tetratomus and Ooencyrtus pinicolus; the larval parasitoids Aleiodes esenbeckii sp. dendrolimi, Cotesia spp., and Glyptapanteles liparidis; and the dipteran pupal parasitoids Masicera sphingivora, Tachina sp., and Blepharipa sp. Their potential should be further explored in order to develop biocontrol programs for this important forest pest.

Most lepidopteran species have a WZ/ZZ sex chromosome system, suggesting a common origin. However, the exceptional variability of W chromosomes supports their multiple independent origins. Here, we investigated the genome of the recently formed species, Dendrolimus sibiricus, which is one of the most devastating pests of the boreal forests in Northern Asia. We found that its karyotype consists of 30 pairs of chromosomes and follows the WZ/ZZ sex chromosome system. We produced a chromosome-scale assembly of its female genome and identified the sequences of both sex chromosomes. With the exception of the W chromosome, the D. sibiricus genome displays a very high degree of synteny with genomes of other Dendrolimus representatives. The non-conserved W chromosome is composed entirely of recently acquired sequences, mainly young genomic repeats and a few unique loci derived from subtelomeric regions of the same species' Z chromosome as well as from the genome of the endosymbiotic Wolbachia bacterium. It shares no common ancestral sequences with the W chromosomes of two related species, Dendrolimus tabulaeformis and Lasiocampa quercus. They, in turn, display a similar organization relative to the W of D. sibiricus, including Z-derived loci. The W of D. tabulaeformis also contained multiple fragments of the mitochondrial genome, as seen in classical B chromosomes. We conclude that W chromosomes arose from their Z counterparts recently and independently in these three species. We propose that this mechanism may be a common feature of lepidopteran evolution, counteracting the inevitable degeneration of a non-recombining chromosome through its repeated, complete turnover.

Trichogramma is an important genus of egg parasitoids, applied against agricultural and forest lepidopteran pests. Known species differ in host specificity, which affects both their efficiency in field and suitability for mass rearing. In 2022, a novel strain of T. dendrolimi was recovered from eggs of the Siberian silk moth Dendrolimus sibiricus in Eastern Siberia. Freshly laid eggs of lepidopteran insects belonging to 17 species were exposed to adult T. dendrolimi. Besides the original host, successful reproduction was observed in the eggs of 13 species belonging to the families of Sphingidae (3 species), Noctuidae (2 species), Pyralidae (1 species), Crambidae (1 species), Erebidae (3 species), Gelechiidae (1 species), Geometridae (2 species), Nolidae (1 species), and Lasiocampidae (3 species). The maximum parasitoid yield of 33 adults per egg was observed in D. sibiricus, followed by Dendrolimus pini (32 adults/egg), Macrothylacia rubi (27 adults/egg), Manduca sexta (26 adults/egg), Orgyia antiqua (4 adults/egg), Pseudoips prasinana (3 adults/egg), Mamestra brassicae, Angerona prunaria, and Chrysorithrum flavomaculata (2 adults/egg), as well as Hydraecia micacea, Ostrinia nubilalis, Galleria mellonella, and Sitotroga cerealella (1 adult/egg). Thirty generations were successfully reproduced in the laboratory using D. sibiricus, M. sexta, M. brassicae, and S. cerealella eggs. The parasitoid remained viable and efficiently attacked eggs of various lepidopteran hosts. The present study extends the knowledge of susceptible hosts of T. dendrolimi. Some of these host species provide high reproduction indices of the parasitoid and could be used for large scale propagation of this biocontrol agent.

The article presents the results of a 5-year experiment on the cultivation of Siberian spruce seedlings combined with integrated use of biostimulants. Additionally, it describes an experience in application of the acquired planting material to artificial reforestation. The analysis of scientific publications was used for type selection of the chemical substances. The treatment for the seeds and the seedlings of Siberian spruce and the concentration of the growth promoters were chosen according to the “State Catalog of Pesticides and Agrochemicals Permitted for Use on the Territory of the Russian Federation”. For this purpose, the recommendations from manufacturers were also taken into concern. It is revealed that Ferovit (0.1 %) and Cytovite (0.01 %) are effective as pre-sowing treatment of the Siberian spruce seeds. Epin-Extra and Heteroauxin with concentrations of 0.002 % give a positive effect on the root development of the seedlings. The experiments showed that a certain sequential use of biostimulants at different stages of the seedling’s cultivation contributes to more intensive biochemical processes inside the plants (an increase in chlorophyll a, b, and carotenoids) with a positive correlation between height and phytomas in aerial parts. The combinations of the biostimulants, such as Ferovit–Heteroauxin and Cytovite–Epin-Extra–Heteroauxin, have improved the plant material within three years. The seedlings satisfied the requirements for the trunk’s height and diameter. They also demonstrated higher quality parameters, such as the proportion between aerial part and root system of the plants, as well as woodiness of the trunks. At the end of the nursery period, the planting material of Siberian spruce, cultivated according to the developed technology with all the requirements and regulations, was used to create a trial plot of forest. The reforestation of the Siberian spruce seedlings was made based on the standard recommendations and technical characteristics for the forestry equipment. The inventory inspection at the end of the first year demonstrated 98.7 % capacity for survival of the experimental trees. For citation: Ageev A.A., Saltsevich Yu.V., Buryak L.V. Integrated Application of Biostimulants in Cultivation of Siberian Spruce Seedlings (Picea obovata L). Lesnoy Zhurnal = Russian Forestry Journal, 2023, no. 2, pp. 73–87. (In Russ.). https://doi.org/10.37482/0536-1036-2023-2-73-87

The Siberian moth, Dendrolimus sibiricus Tschetverikov, is one of the most destructive conifer pests in Northern Asia, causing severe ecological and economic losses. In Russia, its range overlaps with that of the closely related pine-tree lappet Dendrolimus pini (L.), and this raises the potential for hybridization and complicates accurate identification, particularly in the context of the potential westward expansion of D. sibiricus. Here, we present the first comprehensive morphometric analysis of male genitalia aimed at distinguishing these two major forest pests and their hybrids. The study was based on D. sibiricus and D. pini specimens collected during the last 130 years (1894–2024) across Europe and Asia, including their hybrids reared indoors by crossing D. pini females with D. sibiricus males in 1956 and preserved in the collection of the Zoological Institute of the Russian Academy of Sciences (St. Petersburg, Russia). Overall, 70 permanent genitalia slides were prepared (33 D. sibiricus, 33 D. pini, and 4 hybrids), and the following genital structures were measured: valva and harpe length, aedeagus width and length, and cornuti length. Dendrolimus sibiricus had significantly larger genital structures compared to D. pini: 74% longer harpe, 32% longer valva, and a 28% wider and longer aedeagus. In contrast, in D. sibiricus cornuti were 21% shorter than in D. pini. Hybrids displayed intermediate values for valva, harpe, and aedeagus lengths, and for these parameters, they significantly differed from both parental species. The following diagnostic indices were suggested to distinguish between the two species and their hybrids: Harpe Length/Valva Length Index (HL/VL) and Cornuti Length/Aedeagus Length Index (CL/AL). Decision-tree analysis identified HL/VL as the strongest predictor for separating the parental species and the Combined Genital Proportion Index (CGPI), which integrates harpe, valva, aedeagus, and cornuti lengths, as the strongest predictor for identifying hybrids. The morphometric criteria developed here have practical applications for monitoring programs and quarantine diagnostics, particularly in sympatric zones and regions at risk of D. sibiricus expansion.

Polygraphus proximus Blandford is a bark beetle that has recently invaded the dark coniferous forests of Southern Siberia. Over the last decade, this four-eyed fir bark beetle has destroyed Abies sibirica Ledeb stands on more than 500 thousand hectares. This study considers the initial stages of natural reforestation, which can define the restorative succession scenario for completely dead forest stands after the outbreak fades. Areas disturbed by outbreaks have a strong potential for natural coniferous regeneration when the young generation of Abies sibirica dominates in species composition. As early as 5 years after the outbreak, a successful, sufficient for the future forest formation, young generation density (13,000 trees/ha) is observed. Intensive undergrowth development is noted. The high density of young stands in some areas ensures the canopy closure and forms a shady ground cover vegetation type. At the same time, in some disturbed areas there are threats to undergrowth. In open places with thin undergrowth, a considerable amount of forest fuels represented by large wood residues and dead grass accumulates and can cause high-intensity fire emergence and development. Another risk is human activity. In former outbreak foci, where clear-cutting was implemented, healthy trees were cut down and the existing young coniferous generation was destroyed. To date, clearings have been overgrown with secondary species (Betula pendula Roth., Populus tremula L.). Ground cover communities have transformed into open-type phytocenosis where cereal grasses prevail. This has led to turfing and significant litter and dry grass accumulation. To sum up, in faded Polygraphus proximus outbreak areas, strong young forest generation ensures reforestation without dominant species change. To reduce risks of species change and conserve valuable Abies sibirica species, it is necessary to strengthen wildfire protection.