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The pine moth, Dendrolimus houi (Lajonquiere), is a notorious insect pest of coniferous trees in South China. A gregarious egg parasitoid in the family Scelionidae shows great potential to be mass-reared for the biological control of D. houi . This parasitoid is identified as Telenomus dendrolimi (Matsumura) based on comparison to paratype specimens of Telenomus dendrolimusi Chu, a junior synonym of T. dendrolimi . Telenomus dendrolimi is redescribed and included in a molecular analysis. In addition to parasitizing D. houi , T. dendrolimi was found to successfully parasitize six other species under laboratory conditions, with Antheraea pernyi (Guérin-Méneville) the most suitable host for mass-rearing.

Climate change challenges forest vitality both directly by increasing drought and heat periods and indirectly, e.g., by creating favorable conditions for mass outbreaks of phyllophagous insects. The large forests dominated by Scots pine ( L.) that cover the lowland regions in northeast Germany have already been affected regularly by cyclic mass propagations of defoliating insect species in the past with climate projections implying an even more advantageous environment for devastating outbreaks in the future. To improve predictive and responsive capacities we have investigated a wide range of ecological parameters to identify those most strongly related to past outbreak waves of three central species. In total, we analyzed 3,748 variables covering stand and neighborhood properties, site quality, and climatic conditions for an area of roughly 750,000 ha of pine forests in the period 2002-2016. To reflect sensitivity against varying climate, we computed \"floating windows\" in relation to critical phenological phases of the respective insects. The parameters with the highest explanatory power resulted from the variable importance measures of the Random Forest (RF) methodology and have been evaluated by a 10-fold cross-validation process. Our findings closely reflect the known specific gradation patterns and show that relative variable importance varies with species. While L. feeding was mainly dependent on the surroundings of the respective stand, L. proved to be almost exclusively susceptible to climatic effects in its population dynamics. L. exhibited a mixed pattern of variable importance involving both climatic and forest structure parameters. In many cases the obtained statistical results support well-known ecological cause-effect relations and long-term population change dynamics. The RF delivered very high levels of sensitivity and specificity in the developed classifications and proved to be an excellent tool to handle the large amounts of data utilized for this study. While the presented classification approach may already support a better prognosis of the amplitude during the outbreak culmination, the obtained (most important) variables are proposed as preferable covariates for modeling population dynamics of the investigated insect species.

Insecticides based on crystalline toxins of Bacillus thuringiensis are very good biological plant protection products. However, the spectrum of activity of some toxins is narrow or resistance among insects has been developed. We tested the insecticidal activity of crystals of the B. thuringiensis MPU B9 strain alone and supplemented with Vip3Aa proteins against important pests: Spodoptera exigua Hübner (Lepidoptera: Noctuidae) , Cydia pomonella L. (Lepidoptera: Tortricidae) and Dendrolimus pini L. (Lepidoptera: Lasiocampidae). The Cry toxins were more active for D.   pini but less active against S.   exigua and C.   pomonella than Vip3Aa. Supplementation of Cry toxins by small amounts of vegetative insecticidal proteins demonstrated synergistic effect and significantly enhanced the toxicity of the insecticide. The results indicate the utility of Cry and Vip3Aa toxins mixtures to control populations of crops and forests insect pests.

Monitoring of insect pests and aerial spraying of insecticides have proven to be effective in protecting forests against needle-feeding insect pests. However, the literature on the economic viability of insect monitoring and aerial spraying of insecticides is scant. This research conducts a cost–benefit analysis of monitoring insect pests and use of insecticides for 5600 ha of managed pine forests. The case studied is the mass outbreak of the pine tree lappet moth (Dendrolimus pini L.) in Brandenburg (Germany) in 2014. Costs were estimated based on information from standardized questionnaires and semi-structured expert interviews. Benefits were analyzed by comparing the loss of revenue due to D. pini with the costs of insect monitoring and insecticide spraying in two scenarios of pine production (with protection vs. without protection). The results show that monitoring D. pini and aerial spraying of insecticides are economically beneficial to forest owners. The total net present value (NPV) of protection was about EUR 1965 ha−1 at a discount rate of 0% and the benefit–cost ratio (BCR) was about 22.14. NPVs and BCRs per hectare were highest for protecting stands with high site index and stands in the age class of 20–39 years. Sensitivity analyses revealed that NPV results are more sensitive to changes in timber prices than to changes in protection costs. The authors conclude that monitoring insect pests and aerial spraying of insecticides are economically viable options to protect forests against needle-feeding insect pests.

Research highlights: The pine-tree lappet moth, Dendrolimus pini, can cause serious needle defoliation on pines with outbreaks occurring over large geographical areas. Under laboratory conditions, the promising potential of the naturally occurring entomopathogenic fungus Beauveria bassiana was tested against D. pini larvae as a biological control method. Background and objectives: The aim of this study was to investigate the most effective concentration and treatment dose of B. bassiana conidial suspension and how it affected the survival and feeding behavior of the pest. Materials and methods: The first experiment applied the fungal suspension directly on the back of selected larvae, and in the second experiment, sporulating cadavers obtained in the first experiment were placed into Petri dishes with healthy individuals. Different doses per larvae [µL] and spore suspension concentration [spores/µL]) were used. The second experiment was designed to investigate the horizontal transmission of fungi by exposing individual caterpillars to a cadaver covered in B. bassiana mycelia. Mortality rates were analyzed by Chi-squared tests using absolute values for total mortality and B. bassiana- attributed mortality. The lethal time and feeding-disruption speed were analyzed with parametric and non-parametric tests with the aim to determine whether statistically significant differences were observed between treatments. Results: Analysis of lethal time revealed that the 20 µL dose and 7.9 × 104 concentration yielded highest mortality, but also the average dieback rate of 9.4 days was significantly faster compared to all other treatments. In order to see whether insects stopped feeding after infection with B. bassiana, larvae weight loss was examined. Results showed that effective treatments induced change in the feeding behavior of infected larvae. The feeding disruption caused by the 20 µL treatment occurred on average 5.5 days after exposure or 3.9 days before the final dieback of larvae.

In the present work, we sampled individuals of the processionary pine moth, Thaumetopoea pityocampa (Denis and Schiffermüller; Lepidoptera: Notodontidae) from different areas of Greece between 2014 and 2016. These samples were sequenced for a 760-bp long mtDNA COI locus and the haplotypes retrieved clearly showed that the occurrence of T. pityocampa in Greece is being considerably restricted, with only 8 individuals out of the 221 exhibiting T. pityocampa haplotypes and the rest being identified as T. pityocampa ENA clade haplotypes. To that, one haplotype in particular exhibited the highest abundance and broadest geographic distribution, occurring both in mainland and on islands. Our data suggest a rather recent and rapid population expansion of the ENA clade in Greece and a concomitant recent displacement of T. pityocampa. It thus seems that the relation between T. pityocampa and T. pityocampa ENA clade needs to be further and thorough analyzed before the taxonomic status of T. pityocampa ENA clade can be concluded with confidence.

The pine-tree lappet moth, D. pini, is a harmful defoliator of pine forests in Europe and Asia and a potentially invasive species in North America. The lures for trapping D. pini males based on two known components of its sex pheromone appeared weakly attractive to male moths. Identification of all components of the sex pheromone might allow for the development of more effective lures. The pheromone was sampled from virgin females using SPME and analyzed using gas chromatography coupled with mass spectrometry. Four new likely components ((Z5)-dodecenal, (Z5)-dodecen-1-ol, (Z5)-decen-1-yl acetate, (Z5)-tetradecen-1-yl acetate) and two known components ((Z5,E7)-dodecadienal, (Z5,E7)-dodecadien-1-ol) were identified based on comparison against authentic standards, Kováts indices and spectra libraries. The samples also contained several sesquiterpenes. Wind tunnel and field experiments showed that some blends of synthetic pheromone components alone or enriched with Scots pine essential oil (SPEO) were attractive to D. pini males. One component—(Z5)-decen-1-yl acetate—had a repelling effect. The presented knowledge of D. pini sex pheromone provides a basis for developing optimal lures for monitoring or controlling insect populations.

Thousand Island Lake (TIL) is a typical fragmented landscape and an ideal model to study ecological effects of fragmentation. Partial fragments of the mitochondrial cytochrome oxidase subunit I gene of 23 island populations of Dendrolimus punctatus in TIL were sequenced, 141 haplotypes being identified. The number of haplotypes increased significantly with the increase in island area and shape index, whereas no significant correlation was detected between three island attributes (area, shape and isolation) and haplotype diversity. However, the correlation with number of haplotypes was no longer significant when the ‘outlier’ island JSD (the largest island) was not included. Additionally, we found no significant relationship between geographic distance and genetic distance. Geographic isolation did not obstruct the gene flow among D. punctatus populations, which might be because of the high dispersal capacity of this pine moth. Fragmentation resulted in the conversion of large and continuous habitats into isolated, small and insular patches, which was the primary effect on the genetic diversity of D. punctatus in TIL. The conclusion to emphasize from our research is that habitat fragmentation reduced the biological genetic diversity to some extent, further demonstrating the importance of habitat continuity in biodiversity protection.

Dendrolimus pini is one of the most harmful defoliators of Scots pine in Poland and other countries in Europe and Central Asia. The monitoring of this insect needs to be improved and to include the use of pheromone traps. Laboratory studies were conducted to compare changes in the residual amounts of (Z,E)-5,7-dodecadienal and (Z,E)-5,7-dodecadien-1-ol, the major components of the D. pini pheromone, in four types of dispensers. The two most promising dispensers, red rubber cylindrical dispensers (rubber cylinders) and polyethylene vials, were tested in the field for their ability to attract D. pini males. In addition, the effects of trap type (sticky wing, non-sticky cross-vane, bucket, funnel and modified gypsy moth milk carton) and height of trap placement (1.5 m, 5–6 m and tree crown) on trap catches were tested in the field. The vials provided the longest half-lives for both the aldehyde and alcohol under laboratory conditions. These dispensers were also significantly more effective in attracting D. pini males to the traps than the rubber cylinders in the field experiment. The cross-vane and bucket traps were the most effective among the tested traps. The height of trap placement had a significant effect on catches, with more males caught in traps that were hung at 5–6 m above the ground than those hung in the tree crowns. Our results may be useful for developing a monitoring system for D. pini in Europe and other regions where it occurs.

The number of larval instars is important from both theoretical and practical perspectives. Three previous studies based on head capsule widths (HCWs) have suggested that Dendrolimus pini larvae pass through seven instars, but the estimated HCW means differed greatly. Various methods are available for determining the number of instars; however, these methods have not been compared on the same dataset. Therefore, the main goal of this study was to compare three approaches for instar separation in D. pini larvae: visual approach followed by non-linear least squares (NLLS) estimation, kernel density estimation (KDE) followed by NLLS, and model-based clustering. Two criteria were used to assess whether the resulting instar separations adhered to Brooks-Dyar’s rule: Crosby’s growth rule and a coefficient of determination indicating the goodness of fit of a straight line to the ln-transformed mean HCW of the respective instars. Our results showing that D. pini larvae pass through eight instars differed greatly from reports in the literature. The best results were obtained by KDE followed by NLLS. For proper instar separation, both criteria of Brooks-Dyar’s rule must be met.