Search Results (115)

Bark beetle infestations present a considerable risk to coniferous forest ecosystems, resulting in substantial ecological and economic losses. Monitoring and mapping vegetation health using remote sensing techniques is an important step in identifying and controlling areas of susceptibility, especially for bark beetles that cause significant damage to forest ecosystems. This study assessed the statistical discriminative efficacy of vegetation indices obtained from Landsat 8 OLI data at the stand level in discriminating between forest stands impacted and unaffected by Ips sexdentatus damage. Eighty forest stands (40 forest stands, both with and without Ips sexdentatus damage) selected through fieldwork in the Araç Forest Directorate, Kastamonu, were studied. Five frequently utilized vegetation indices (NDVI, NDMI, MSI, TCW, and RGI) were applied, and the minimum, maximum, and average values were computed for each stand. Given the non-normal distribution of the data, the Mann–Whitney U test was utilized, revealing significant differences (p < 0.001) between stands with and without beetle damage across all indices except TCW(max.). NDVI and NDMI values decreased in damaged stands, whereas MSI and RGI values increased. MANOVA results indicated substantial distinction among groups (Pillai’s Trace = 0.870, p < 0.001), whereas PCA demonstrated significant differentiation, accounting for 75.4% of the total variance. The mean values of NDVI and NDMI showed the greatest discriminatory potential among the indices. In summary, the Landsat 8 vegetation indicators tested in this study showed substantial discriminating potential. Full article

Bark beetle–fungus associations are essential for nutrition, detoxification, and host colonisation, but their composition and function vary across developmental stages and environmental contexts. Hence, we characterised the fungal communities associated with two pine-feeding bark beetles, Ips sexdentatus (ISX) and Ips acuminatus (IAC), across developmental stages and compared wild-collected and laboratory-bred populations using ITS2 amplicon sequencing. Both beetle species maintained a stable core mycobiome dominated by Kuraishia, Ogataea, Ophiostoma, Graphilbum, and Cyberlindnera. These taxa have been earlier reported to be associated with nutrient provisioning, detoxification of host secondary metabolites, and chemical signalling. Adult beetles showed species-specific community differences, whereas wild-collected beetles, particularly IAC, harboured higher fungal diversity than laboratory populations, indicating a strong environmental effect. Beetles shared more fungal taxa with control wood than with gallery wood, suggesting possible fungal acquisition during feeding and concurrent restructuring of the wood mycobiome during infestation. Monoterpene bioassays with selected yeast symbionts showed differential growth responses to α-pinene, 3-carene, and terpinolene, and their mixture, with the mixture producing stronger inhibition than individual compounds. These yeast symbionts further displayed selective antagonistic activity in vitro against selected filamentous fungi, including entomopathogenic taxa, along with detectable lytic and digestive enzyme activities. Together, our findings highlight a link between community structure, predicted functions, and observed interaction phenotypes, providing a strong basis for future mechanistic studies of beetle–fungus–conifer interactions. Full article

Ips typographus is one of the most destructive bark beetles affecting conifer forests in Europe, where climatic disturbances and the movement of infested wood can rapidly shift populations from endemic levels to severe outbreaks. Early detection through border inspections and forest monitoring is essential to prevent new introductions and limit the spread of established populations. Here, we developed and validated a probe-based TaqMan qPCR assay, targeting the mitochondrial COI barcode region, for the rapid and species-specific detection of I. typographus from both insect material and environmental DNA recovered from frass and exit-hole wood chips. Validation followed EPPO PM7/98(5) guidelines, assessing analytical specificity, sensitivity, repeatability, reproducibility, and inter-laboratory transferability. High analytical specificity was demonstrated against a broad panel of non-target species, and reliable amplification was obtained across different tested matrices. The method showed strong analytical sensitivity, with limits of detection of 0.32 pg/µL for adult-derived DNA and 1.6 pg/µL for artificial frass. Repeatability, reproducibility, and inter-laboratory blind testing further confirmed the diagnostic reliability of the method. This validated qPCR assay provides a rapid and sensitive molecular tool for the early detection of I. typographus, supporting border inspection and phytosanitary diagnostic laboratories in forest biosecurity activities. Full article

Forest pests and diseases are some of the major disturbances affecting the stability of forest ecosystems. Accurate identification of insect-infested trees is therefore crucial for assessing forest health and implementing precision forestry management. This study focuses on stand-level detection of cypress trees (Cupressus funebris Endl.) that were affected by the cypress bark beetle (Phloeosinus aubei Perris), and the framework enables individual tree segmentation, insect-infested tree detection, and stand infestation assessment. Firstly, individual trees were extracted from Light Detection and Ranging (LiDAR) point cloud data using the layer-stacking seed point algorithm. Based on the segmented tree crowns, four vegetation indices (Visible Atmospherically Resistant Index (VARI), Visible-band Difference Vegetation Index (VDVI), Red-Green Index (RGI), and Color Index of Vegetation Extraction (CIVE)) were calculated from Unmanned Aerial Vehicle (UAV) RGB imagery. Insect-infested cypress trees were extracted through threshold segmentation. Through visual interpretation, the optimal vegetation index was determined and the infestation rate at the stand level was calculated. Based on the above framework, a total of 1368 trees were identified in the cypress stand, with a segmentation Precision of 82.51%, a Recall of 80.00%, and an F1-score of 81.24%. RGI achieved the best performance (Precision = 100.00%, Recall = 86.96%, F1-score = 93.02%) and identified 20 infested trees, accounting for 1.46% of the cypress stand. Supplementary experiments further confirm the superiority of the RGI index and the μ ± 2σ thresholding method. These results demonstrate that the proposed method enables rapid detection of the infested cypress trees, effective monitoring of stand health and infestation severity, thereby supporting informed decision-making in pest control and forest management. Full article

Outbreaks of Ips hauseri, a major bark beetle pest in Central Asian Picea schrenkiana forests, have intensified under climate warming and prolonged droughts. However, the reproductive behavior and gallery construction strategies of this species remain poorly understood, limiting our ability to predict its population dynamics. Here, we dissected 219 galleries from infested spruce trees in Hami, Xinjiang, during an outbreak period (2024–2025). We identified 11 distinct gallery morphologies, with harem size (number of females per male) ranging from one to seven. Gallery length was positively correlated with egg production. Reproductive output peaked at a harem size of five, beyond which both gallery dimensions and fecundity declined. Host tree diameter at breast height (DBH) significantly influenced gallery complexity, with larger trees supporting more maternal galleries. Upward-oriented galleries were longer and contained more eggs than downward ones. Intraspecific competition, mediated by gallery adjacency and spatial orientation, strongly affected offspring development. Our results demonstrate that I. hauseri exhibits flexible gallery architecture and reproductive adjustments in response to resource availability and competition—a behavioral plasticity that likely contributes to its outbreak potential. Monitoring gallery morphology and harem size could enhance early detection and population forecasting for this increasingly damaging forest pest. Full article

Southern pine beetle infestations impact ecosystems throughout the southeastern US. Our understanding of hydrologic and biogeochemical impacts on ecosystem structure and function is largely guided by severe outbreaks occurring in the western US. A simulated mortality experiment was conducted on loblolly pine trees via girdling with and without blue-stain fungi inoculation to mimic a small-scale infestation. We measured whole-tree water use, canopy-derived hydrologic and biogeochemical fluxes, soil moisture, and soil respiration for two years following treatments to quantify the impacts of tree mortality on water, carbon, and nitrogen cycles. In the second year of our study, a significant drought occurred, subjecting study trees to a secondary stressor. We found that compared to control trees, girdled trees exhibited reduced water uptake within 6 months and succumbed to mortality within 18 months. We found that by the time trees reached the gray phase of attack, stemflow was 1.7-times lower in girdled trees compared to control trees. Stemflow from girdled trees had up to 7.2-times higher concentrations of ammonium and 2.8-times higher concentrations of total nitrogen. Although stemflow carbon concentrations were indistinguishable between treatments, total carbon flux in stemflow was 2.0-times greater in non-girdled trees (p = 0.030). Finally, even though soil moisture and respiration were not different between treatments, it was not possible to isolate the response of these to mortality versus drought. Our results present the connection between bark beetle outbreaks and the initial impacts on forest biogeochemistry. Changes in the distribution of canopy-derived water inputs, coupled with altered carbon and nitrogen fluxes, serve as hot spots around bark beetle-killed trees. Further research is necessary to understand whether these isolated hot spots may prime the system, alter microbial and invertebrate communities, and lead to changes in decomposition processes at larger scales. Full article

Bark beetle infestations and other natural disturbances have increasingly affected Norway spruce (Picea abies (L.) Karst.) forests across Europe resulting in devaluation and decreased applicability of woody biomass of such trees. The aim of this research was to investigate the extractive content of bark beetle-attacked and dead wind-damaged Norway spruce trees relative to healthy trees, in order to assess their potential for extractives recovery. After harvesting, three discs were dissected along the stem height of each tree, and samples of sapwood, heartwood, knots, and bark were collected. Sequential extraction of the samples was performed using cyclohexane and acetone–water mixture in an accelerated solvent extractor. Lipophilic and hydrophilic extractives were determined gravimetrically, while total phenols and proanthocyanidins were measured by UV–Vis spectrophotometry. Results showed that knotwood contained the highest amounts of hydrophilic extractives and total phenols among investigated tissues. Knots of healthy trees contained the highest amount of hydrophilic extractives (52.4% w w⁻¹), while knots of dead wind-damaged trees contained significantly higher content of total phenols (8.8% w w⁻¹). The total phenols in bark beetle-attacked and healthy trees were 7.1% w w⁻¹ and 7.2% w w⁻¹, respectively. The sapwood and heartwood of dead wind-damaged trees had higher content of hydrophilic extractives (3.4% and 2.3% w w⁻¹) than healthy and bark beetle-attacked trees. Bark from healthy trees contained more total phenols (2.7% w w⁻¹) than bark of bark beetle-attacked trees, while proanthocyanidin contents in bark were comparable among three groups of trees. Our findings revealed that woody biomass from bark beetle-attacked and dead wind-damaged Norway spruce trees contains significant levels of phenolics, indicating high potential for extracting valuable compounds in biorefineries. Full article

Recent intensive research on the cypress bark beetle, Phloeosinus aubei was prompted because of its invasion of Central Europe that caused serious damage to scale-leaved conifer ornamental trees. This dynamic also increased the risk of accidental introduction into North America. In contrast to other historically well-studied bark beetles infesting spruce, pine or broad-leaf trees, intense study of the pheromones and host plant kairomones of bark beetles associated with cupressaceous trees has only begun in the past decade. This highly specialized clade is represented by the genus Phloeosinus. The pressing need for semiochemical-baited traps demands the identification of behavior-modifying compounds. This challenge involves unraveling the various stimuli interacting in the complex communication system to reveal the composition of signal bouquets and the absolute configuration of their components capable of evoking behavior responses. In this short overview we describe the recent research results on host-finding and intraspecific chemical communication of P. aubei, with a short outlook on the species of this genus. Full article

Understanding how forests recover after severe disturbances is essential for developing effective management strategies that promote stable forest regeneration. Disturbances are particularly significant in transition zones such as treelines, which are highly sensitive to climate change. In the subalpine treeline ecotone of Zao Mountains (northeastern Japan), a severe double-pest infestation devastated the Abies mariesii forest, triggering a treeline retreat of nearly 400 m. Prior to the infestation, the stand density was estimated at 3135 (based on the sum of standing living and dead standing trees and fallen trees detected in the orthomosaics generated for the year 2019). Of these, 3023 were standing trees (of which 2787 were dead). By 2025, the number of standing trees had declined to 2472 (18.2% reduction), a significant development for Abies seedlings, which appeared to establish in decaying fallen logs. In order to evaluate whether this disturbance has permanent or temporary effects, high-resolution unmanned aerial vehicle (UAV) imagery was collected annually over the study area, resulting in six orthomosaics from 2019 to 2025 (2020 data unavailable) for continuous and precise forest monitoring. Analysis of the monitored area revealed that in the 6.9 ha study site, entirely covered by 1.2–1.3 m tall sasa vegetation (Sasa kurilensis), the number of new young trees increased from 60 (2019) to 119 in 2025. These younger trees were mainly located near surviving mature trees. Sasa vegetation did not exert a negative effect on regeneration but instead appeared to function as a strong wind protection, facilitating Abies seedling growth. In conclusion, fallen logs and sasa vegetation appeared to have a positive effect on fir regeneration as suggested by the increasing number of young trees observed over time. The bark beetle outbreak functioned as a forest stand-replacing disturbance, where the subalpine fir forest at the treeline is expected to regenerate naturally within the coming decades. Full article

The red-haired bark beetle (RHB), Hylurgus ligniperda (Fabricius, 1787) (Coleoptera: Curculionidae: Scolytinae), is a globally distributed quarantine pest, making effective management of infested wood essential. This study developed an integrated control system to achieve closed-loop management under various environmental and wood conditions. RHB eggs were the most fumigation-tolerant stage. Although sulfuryl fluoride (SF) showed higher potency, aluminum phosphide (AP) provided deeper penetration into wood (AP: 29.5% vs. SF: 12.6%). Both fumigants effectively reached all logs in the stacks. Fumigation efficacy was highest at moderate temperatures (18–22 °C) and lower wood moisture levels. In addition to chemical methods, thermal treatments were evaluated: heating to 60–65 °C achieved complete mortality, while effective freezing control required temperatures of −30 °C. For bark and chip debris generated during processing, beta-cypermethrin fumigation effectively eliminated residual pests. Our results confirm that both AP and SF are suitable for disinfecting infested Pinus thunbergii wood, that extreme temperatures can reduce dispersal risks, and that beta-cypermethrin is effective in the downgraded utilization of wood byproducts. This work provides a comprehensive and practical framework for controlling the spread of this invasive pest. Full article

Bark and ambrosia beetles (Coleoptera: Curculionidae: Scolytinae) are major pests of agricultural and forest systems and include some species which attack hazelnut (Corylus avellana L.) as well. Although hazelnut cultivation is increasingly threatened by insect and mite pests, yet little is known about how management practices can reduce infestations. This study investigated bark and ambrosia beetles in hazelnut orchards from two highly productive areas: Viterbo district (central Italy) and Samegrelo-Zemo Svaneti region (Republic of Georgia). Three phytosanitary management strategies were compared across 2023–2024: Integrated Pest Management, organic farming, and renaturalised orchards. Monitoring also evaluated three ethanol-baited trap designs: three designs in Italy (handmade red funnel [BR] and bottle [TT] and commercial multi-funnel [MF]) and only TT in Georgia. Anisandrus dispar, Hypothenemus eruditus, Xyleborinus saxesenii, and Xylosandrus germanus were detected in both countries, while Xyleborus monographus occurred only in Italy. Xyleborinus saxesenii was the dominant species in both regions. Beetle populations differed among management strategies, being lowest in organic orchards and highest in integrated and renaturalised systems. Trap performance also varied, with BR consistently outperforming commercial MF. These findings highlight the influence of management and monitoring tools on scolytine populations, offering practical insights for sustainable hazelnut production. Full article

Dendroctonus armandi is a native bark beetle that infests healthy Pinus armandii Franch. in western China. The complex symbiotic relationships with diverse microbes are critical to hosts for survival and outbreak dynamics. Understanding the potential functions and assembly metabolisms of these symbiotic microbes to host colonization are therefore crucial. Metagenomic analysis revealed that gut microbial communities differed from cuticular ones significantly. The cuticle exhibited greater fungal diversity, while the gut supported a significantly higher bacterial diversity. Our findings indicated that gut unclassified Burkholderiales, Escherichia, Bacteroides and Prevotella may play a crucial role in degrading terpenes, phenols and polysaccharides rather than cuticular microbes. Stochastic processes appeared to be served as the primary drivers shaping the core microbial community structures. Cuticular dominant and functional microbial community assemblies except for Escherichia may be primarily driven by stochasticity to adapt the unstable habitats. The direct comparison of gut and cuticular microbiomes may provide valuable insights into the specific functions of symbiotic microbes, and offer critical molecular data for broader understanding of symbiotic relationship between bark beetles and microbes. Full article

Climate change is generally having a negative impact on forest health by inducing drought stress and favouring the spread of pest species, such as bark beetles. The terrestrial monitoring of bark beetle infestation is very time-consuming, especially in the early stages, and therefore not feasible for extensive areas, emphasising the need for a comprehensive approach based on remote sensing. Although numerous studies have researched the use of optical data for this task, radar data remains comparatively underexplored. Therefore, this study uses the weekly and cloud-free acquisitions of Sentinel-1 in the Bavarian Forest National Park. Time series analysis within a Multi-SAR framework using Random Forest enables the monitoring of moisture content loss and, consequently, the assessment of tree vitality, which is crucial for the detection of stress conditions conducive to bark beetle outbreaks. High accuracies are achieved in predicting future bark beetle infestation (R² of 0.83–0.89). These results demonstrate that forest vitality trends ranging from healthy to bark beetle-affected states can be mapped, supporting early intervention strategies. The standard deviation of 0.44 to 0.76 years indicates that the model deviates on average by half a year, mainly due to the uncertainty in the reference data. This temporal uncertainty is acceptable, as half a year provides a sufficient window to identify stressed forest areas and implement targeted management actions before bark beetle damage occurs. The successful application of this technique to extensive test sites in the state of North Rhine-Westphalia proves its transferability. For the first time, the results clearly demonstrate the expected relationship between radar backscatter expressed in the Kennaugh elements K₀ and K₁ and bark beetle infestation, thereby providing an opportunity for the continuous and cost-effective monitoring of forest health from space. Full article

Mountains are global biodiversity hotspots but face the danger of habitat loss, especially at lower elevations due to climate-warming-induced forest dieback. In the Gongga Mountains (SW China), Abies fabri trees at 2800 m show increased mortality, yet the causes remain unclear. We assessed climatic influences and bark beetle infestations on tree vigor and radial growth, comparing healthy and declining trees at 2800, 3000, and 3600 m elevations. Leaf nitrogen and phosphorus concentrations were measured to evaluate nutrient status. From 1950 to 2019, mean annual temperatures rose at all elevations, while precipitation decreased at low elevations, negatively correlating with temperature. Such warmer, drier conditions impaired low-elevation trees. The decline in A. fabri growth began in the late 1990s to early 2000s, with an earlier and more pronounced onset at lower elevations. A clear lag is evident, as trees at 3000 m and 3600 m showed either delayed or minimal decline during the same period. High-elevation trees experienced more stable climate and better nutrient availability, supporting greater growth and leaf nitrogen in healthy trees. Bark beetle infestations were worst in declining trees at the highest elevation. Our results reveal that A. fabri vigor shifts along elevation gradients reflect interactions between abiotic and biotic stressors, especially aridification. Full article

Tomicus yunnanensis Kirkendall and Faccoli, a native bark beetle species and key pest of Pinus yunnanensis Franch. in southwestern China, relies on host-derived volatile organic compounds (VOCs) for host selection. To unravel these mechanisms, we collected VOCs from P. yunnanensis trunks across four infestation stages (healthy, early-infested, weakened, near-dead) using dynamic headspace sampling. Chemical profiling via gas chromatography–mass spectrometry (GC-MS) identified 51 terpenoids, with α-pinene as the most abundant component. VOC profiles differed markedly between healthy and early-infested trees, while gradual shifts in compound diversity and abundance occurred from the weakened to near-dead stages. Bioactive compounds were screened using gas chromatography–electroantennographic detection (GC-EAD) and a Y-tube olfactometer. Electrophysiological responses in T. yunnanensis were triggered by α-pinene, β-pinene, 3-carene, 2-thujene, and 4-allylanisole. Behavioral tests revealed that α-pinene, 3-carene, and 2-thujene acted as attractants, whereas β-pinene and 4-allylanisole functioned as repellents. These results indicate that infestation-induced VOC dynamics guide beetle behavior, with attractants likely promoting host colonization during early infestation and repellents signaling deteriorating host suitability in later stages. By mapping these chemical interactions, our study identifies potential plant-derived semiochemicals for targeted pest management. Integrating these compounds with pheromones could enhance the monitoring and control strategies for T. yunnanensis, offering ecologically sustainable solutions for pine ecosystems. Full article