Search Results (129)

The bioinsecticide Bacillus thuringiensis subsp. kurstaki (Btk) is applied over large areas to reduce defoliation caused by the spruce budworm, an insect which affects millions of hectares of coniferous forests every 30 to 40 years in eastern North America. The aim of our study was to determine whether, in addition to its direct lethal effects, aerial spraying of Btk had sublethal effects on spruce budworm populations and their parasitism. Four sites were sprayed with Btk and compared to four control sites in two regions, one where the outbreak had started three years earlier and the other where it had been going on for 10 years. Insects were collected to compare budworm pupal mass and parasitism at different stages (L₅, L₆ and pupae). Budworm pupae were significantly lighter in Btk-treated sites than in controls, and in the older population than in the younger one. However, pupae collected from Btk-treated sites had the same mass in both regions, suggesting a minimum pupal mass threshold, which may affect population dynamics. Larval parasitism was low, but pupal parasitism was high and strongly influenced by an interaction between Btk and region, with a higher parasitism observed in Btk-treated sites of the younger population than in those of the older population. A significant interaction was observed between Btk treatment and region on the proportion of larvae that failed to complete development, which was particularly high in Btk-treated sites of the older population. Our study confirms the effectiveness of Btk in controlling spruce budworm populations directly but also indirectly through sublethal effects on budworm development, capacity to complete development, pupal size and parasitism. To maximize control efficacy, the timing of Btk applications could vary according to the age of populations during the budworm outbreak cycle. Full article

This study investigates spongy moth (Lymantria dispar) infestation patterns in Whirlpool Forest, Ontario, offering a region-specific perspective while largely corroborating existing findings. We analyzed egg mass distribution across 43 sampling plots, relating it to tree characteristics. Results revealed a preference for red oak species, with significant egg-laying above one meter. Positive correlations were found between tree diameter and egg mass quantity (ρ = 0.458, p < 0.001 above 1 m; ρ = 0.218, p = 0.006 below 1 m). Tree health was significantly associated with egg mass presence (χ² = 6.08, p = 0.014). A climate-based regression model (R² = 0.714, p < 0.05) projected substantial increases in outbreak area by 2100, with the most severe scenario predicting 9,927,378.49 hectares at risk. Sensitivity analysis showed a 1 °C temperature increase could expand the outbreak area by 814,100 hectares. These findings underscore complex infestation dynamics, challenging simplified models and emphasizing the need for tailored, adaptive forest management strategies in response to changing environmental conditions and pest behaviors. Full article

Oak forests provide critical ecosystem services, but are being increasingly exposed to climate variability, drought, and insect outbreaks that threaten their long-term resilience. This study aims to integrate structural canopy indicators with climate-derived indices to detect early-warning signals of decline in temperate oak stands. We monitored eight Forest Management Units in western Romania between 2017 and 2021, combining field-based assessments of crown morphology, vitality traits, defoliation, and epicormic shoot frequency with hydroclimatic indices such as the Forest Aridity Index. Results revealed strong spatial and temporal variability: several stands showed advanced canopy deterioration characterized by increased defoliation, dead branches, and epicormic resprouting, while others maintained stable conditions, suggesting resilience and suitability as reference sites. Insect defoliators, particularly Geometridae, contributed additional stress, but generally at subcritical levels. By synthesizing these metrics into conceptual models and a risk scorecard, we identified the causal pathways linking climatic anomalies and biotic stressors to structural decline. The findings demonstrate that combining structural and climatic indicators offers a transferable framework for forest health monitoring, providing robust early-warning tools to guide adaptive silviculture and resilience-based management. Beyond the Romanian context, this integrative approach supports sustainability goals by strengthening conservation strategies for temperate forests under global change. Full article

Ectropis grisescens (Lepidoptera: Geometridae) is a destructive pest in tea plantations, leading to significant economic losses through defoliation. Existing control strategies, including chemical insecticides and biological agents, are often limited by environmental concerns, resistance, and variable efficacy. Recent evidence suggests that bacteria influence insect physiology and could be leveraged for pest management, but the postmortem microbial ecology of E. grisescens remains uncharacterized. In this study, we employed 16S rRNA sequencing to investigate temporal changes in the bacterial communities of E. grisescens cadavers at 0, 7, and 21 days following cryogenic mortality. Our results indicate a time-dependent decline in microbial diversity, while species richness initially increased before subsequent reduction. The dominant endosymbiont Wolbachia gradually diminished after host death, whereas Enterobacter remained abundant. Notably, non-dominant genera including Lysinibacillus and Sporosarcina exhibited a transient increase in abundance at day 7 before reverting to control levels by day 21. This study presents the first comprehensive analysis of postmortem microbial succession in a lepidopteran system, highlighting dynamic shifts in bacterial composition and offering potential avenues for microbiome-based pest management strategies. Full article

Fig (Ficus carica) orchards in the Salento peninsula (southeastern Apulia region, Italy) are increasingly affected by decline syndromes whose etiology remains poorly resolved. In this paper, we provide a first characterization of a complex disease outbreak, integrating field surveys, fungal isolation, molecular phylogenetics, and pathogenicity assays. Symptomatic trees displayed chlorosis, defoliation, cankers, vascular discoloration, and wilting, frequently associated with bark beetle galleries. Mycological analyses revealed a diverse assemblage of fungi, dominated by Botryosphaeriaceae (including Neofusicoccum algeriense, and Lasiodiplodia theobromae), the Fusarium solani species complex (notably Neocosmospora perseae), and Ceratocystis ficicola. While C. ficicola was isolated with lower frequency, its recovery from adult beetles—including Cryphalus dilutus—supports a role in insect-mediated dissemination in addition to soilborne infection. Pathogenicity tests demonstrated that N. algeriense and N. perseae, together with C. ficicola, caused severe vascular lesions and wilting, confirming their contribution to fig decline. By contrast, other Fusarioid strains showed no pathogenicity, consistent with their role as latent or stress-associated pathogens. This study provides the first evidence that N. algeriense and N. perseae act as pathogenic agents on fig, highlights their interaction with C. ficicola within a multifactorial decline syndrome, and identifies dual epidemiological pathways involving both soil/root infection and insect-facilitated dissemination via beetles such as C. dilutus. These findings redefine fig decline in the Salento peninsula (southern Italy) as a multifactorial disease rather than a single-pathogen outbreak, with significant implications for diagnosis, epidemiology, and integrated management strategies. Full article

Pedunculate oak (Quercus robur L.), an ecologically and economically important tree species has been significantly affected by oak dieback in recent years. Since one of the symptoms of oak dieback is crown defoliation, this research aimed to determine the quantity, quality, average tree value, and wood defects that influence grading in different stages of oak dieback indicated by tree crown defoliation degree. The research was conducted in a 62- and 116-year-old stand of the lowland Croatian forest. In total, 115 pedunculate oak trees were sampled and processed in 983 logs that were analyzed. The prescribed single-entry volume tables underestimate harvesting volume by 5.45% on site A and 6.16% on site B, while the calculation of net harvesting volume underestimates net volume by 0.26% on site A and overestimates net volume on site B by 4.59%. The analysis of wood defect presence showed that insect holes, rot, and covered knots were the main reasons for the degradation of quality class. Dead trees showed a decreased average tree value in DBH classes 32.5–42.5 cm compared to the healthy trees. Based on the findings of this research, tree crown defoliation degree could be used as a timber quality and average tree value indicator. Full article

The use of Google Earth Engine (GEE), a cloud-based computing platform, in spatio-temporal evaluation studies has increased rapidly in natural sciences such as forestry. In this study, Sentinel-2 satellite imagery and Shuttle Radar Topography Mission (SRTM) elevation data and image classification algorithms based on two machine learning techniques were examined. Random Forest (RF) and Classification and Regression Trees (CART) were used to classify land use and land cover (LULC) in western Oregon (USA). To classify the LULC from the spectral bands of satellite images, a composition consisting of vegetation difference indices NDVI, NDWI, EVI, and BSI, and a digital elevation model (DEM) were used. The study area was selected due to a diversity of land cover types including research forest, botanical gardens, recreation area, and agricultural lands covered with diverse plant species. Five land classes (forest, agriculture, soil, water, and settlement) were delineated for LULC classification testing. Different spatial points (totaling 75, 150, 300, and 2500) were used as training and test data. The most successful model performance was RF, with an accuracy of 98% and a kappa value of 0.97, while the accuracy and kappa values for CART were 95% and 0.94, respectively. The accuracy of the generated LULC maps was evaluated using 500 independent reference points, in addition to the training and testing datasets. Based on this assessment, the RF classifier that included elevation data achieved an overall accuracy of 92% and a kappa coefficient of 0.90. The combination of vegetation difference indices with elevation data was successful in determining the areas where clear-cutting occurred in the forest. Our results present a promising technique for the detection of forests and forest openings, which was helpful in identifying clear-cut sites. In addition, the GEE and RF classifier can help identify and map storm damage, wind damage, insect defoliation, fire, and management activities in forest areas. Full article

Norway spruce (Picea abies (L.) Karst.) has been widely planted beyond its natural range due to its fast growth rate and valuable wood. In Québec, over 200 million seedlings have been planted since 1964. Several of these plantations are now facing a new potential threat, i.e., spruce budworm (Choristoneura fumiferana (Clem.)) infestations. Despite contrasting results, Norway and white spruce (P. glauca [Moench] Voss) apparently sustain a similar degree of budworm defoliation. The main study objective is to quantify defoliation in Norway spruce caused by spruce budworm. We also evaluate the efficacy of Bacillus thuringiensis Berliner spp. kurstaki (Btk) in protecting this exotic host tree. Annual defoliation was assessed in plantations of Norway, white, and black spruce (P. mariana [Mill.] BSP) between 2018 and 2022 in the Bas-Saint-Laurent region. Additional surveys were conducted in Norway and white spruce plantations in the Gaspésie and Côte-Nord to evaluate Btk efficacy. We show that both species exhibit similar defoliation levels, though Norway spruce sometimes sustains greater damage (e.g., 35% vs. 10% in 2019). Btk formulations showed low efficacy in protecting Norway spruce foliage (≥49.32% defoliation in treated plantations). Further studies are needed to understand factors influencing Btk efficacy on this host. Full article

Red wood ants (RWA), belonging to the Formica rufa species group, play a crucial and fascinating role in Central Europe’s forest ecosystems. They have a high variety of effects, which they exert around their nests. Their generalist feeding on prey in the canopies of trees lowers the frequency of defoliator outbreaks, as well as increases local biodiversity. Nearly half of their diverse diet is insects, including species considered harmful by foresters. They also have a mutualistic relation with honeydew-producing aphids and planthoppers, which connection has unclear effects on the forests. The habit of RWAs building nests could also positively influence soil composition, due to its structure and high amount of organic matter, which could potentially benefit tree growth. RWAs are also known to enhance the species richness of forests by supporting various myrmecophilous species associated with them. In this study, we review the role of RWAs in forest protection, drawing on the literature focusing on Hungary and Central Europe. Full article

Background/Objectives: Pyrrhalta aenescens, a major pest of elm trees, causes extensive ecological and economic damage through rapid population growth and defoliation. Existing research mainly focuses on its biological traits and chemical control, with little knowledge about its reproductive development mechanisms, a key factor in population expansion. In other insects, the steroid hormone 20-hydroxyecdysone (20E) regulates development and reproduction via microRNA (miRNA)-mediated pathways, but this has not been studied in P. aenescens. This study aimed to systematically identify miRNAs responsive to 20E in P. aenescens and unravel their roles in regulating reproduction and metabolic pathways, providing foundational insights into hormone–miRNA crosstalk in this ecologically significant pest. Methods: Adult beetles (collected from Baotou, Inner Mongolia) were injected with 1.0 μg/μL 20E or control. Total RNA from three biological replicates (10 adults each) was sequenced, followed by miRNA identification, differential expression analysis, target prediction, and functional enrichment. Results: Small RNA sequencing identified 205 miRNAs (162 conserved, 43 novel), with 12 DEMs post-20E treatment. Target prediction linked these miRNAs to 7270 genes, including key regulators of the FoxO signaling pathway and MAPK signaling pathway. KEGG analysis highlighted lipid metabolism and stress response pathways. Conclusions: This study revealed that 20E modulates miRNA networks to regulate FoxO and MAPK pathways in P. aenescens, suggesting hormonal control of lipid metabolism and developmental processes. As the first miRNA resource for this pest, our findings provide mechanistic insights into 20E–miRNA crosstalk and identify potential molecular targets for disrupting its reproductive biology, laying a foundation for eco-friendly pest control. Full article

As the effects of climate change progressively worsen, many scientists are concerned over the expanding geographic range and impact of forest-defoliating insects. Many are currently pointing to this form of disturbance becoming a key focus of remote sensing research in the coming decades; however, the available body of research remains lacking. This study investigated the viability of detecting and quantifying damage caused to a managed Scots pine forest in central Poland by insect defoliation disturbance using high-resolution multispectral satellite imagery. Observed leaf area index (LAI) values were compared to frass observations (insect detritus) to assess the relationship between LAI and defoliating insect activity across a single life cycle of A. posticalis Mats. Across four managed plots, four vegetative indices (NDVI, GNDVI, EVI, and MSAVI2) were calculated using multispectral satellite imagery from a PlanetScope (PSB.SD instrument) satellite system. Then, 1137 point-sampled digital number (DN) values were extracted from each index, and a correlation analysis compared each to 40 ground-observed LAI data points. LAI was modeled on the basis of NDVI values. Three models were assessed for their performance in predicting LAI. They were fit using a variety of regression techniques and assessed using several goodness-of-fit measures. A relationship between observed LAI and frass observations was found to be statistically significant (p-value = 0.000303). NDVI was found to be the correlated LAI values (rho = 0.612). Model 3, which was based on concepts of the Beer–Lambert law, resulted in the most robust predictions of LAI. All parameters were found to be significant post fitting of the model using a nonlinear least squares method. Despite the success of the Beer’s law model in predicting LAI, detection of A. posticalis damage was not achieved. This was predominately due to issues of resolution and plot condition, among others. The results of this analysis address many interesting facets of remote sensing analysis and challenge the commonly held view of the impeachability of these methods. Full article

Some Pseudococcidae species interact with Coffea arabica’s roots and are associated with basidiomycete fungi. The fungal mycelium envelops the roots, which hinders their water and nutrient absorption. Combined with the feeding activity of the insects, this results in chlorosis, defoliation, and even plant death. Despite the significance of these interactions, they remain under-studied. To investigate the relationship between sporocarps found at the base of coffee trees, the cysts covering their roots, and the mealybug insects within them, samples of these three organisms—sporocarps, cysts, and mealybugs—were collected from 27 coffee plants across three farms in the departments of Norte de Santander and Quindío, Colombia. Fungi and cysts were identified by sequencing a nuclear gene region of the 28S large ribosomal subunit (28S rDNA) using the primers LSU200-F and LSU481-R. Fungal identification was further confirmed through classical taxonomy. Mealybugs were identified by sequencing a region of the mitochondrial gene Cytochrome C oxidase subunit I (COI) with CIF-CIR primers, corroborated through classical taxonomy. This study identified four fungal species associated with four species of Pseudococcidae. The fungus Phlebopus beniensis was associated with the mealybugs Pseudococcus elisae, Dysmicoccus neobrevipes, D. brevipes, and Pseudococcus nr. sociabilis. Phlebopus portentosus was linked to D. neobrevipes, while Xerophorus olivascens and Boletinellus rompelii were associated with other Pseudococcidae species. Additionally, the fungus Pseudolaccaria pachyphylla was found in coffee plants harboring mealybugs. These findings confirm the existence of specific associations between fungal species and mealybug insects that affect coffee plants. Full article

Soybean (Glycine max) is the most widely grown legume crop in the world, providing important economic value. Pest herbivory damage by insects and mammalian wildlife, in particular the white-tailed deer (Odocoileus virginianus), limits yields in soybean. Incorporating trypsin inhibitors (TIs) as plant protectant against herbivory pests has been of interest. We previously showed that the overexpression of soybean TIs in soybean conferred insect deterrence under greenhouse experiments. In this study, we examined the potential of transgenic TI-overexpressing lines in deterring insects under field conditions at Knoxville, Tennessee. Our results indicate that the overexpression of TI could lead to a significant reduction in leaf defoliation of the transgenic compared to non-transgenic lines without negatively impacting plant growth and yield under field conditions. Furthermore, we extended our study by comprehensive evaluation of these transgenic plants against the white-tailed deer herbivory in a separate field setting at Jackson, Tennessee, and with controlled deer feeding experiments. No significant differences in growth characteristics were found between transgenic and non-transgenic lines under field conditions. There were also no significant differences in deer deterrence between transgenic and non-transgenic lines in ambient deer herbivory field or controlled deer feeding trials. Our study provides further insights into more exploration of the role of TI genes in pest control in this economically important crop. Full article

The functioning of ecosystems critically depends on biodiversity. However, the effects of herbivore diversity on plant damage caused by herbivore feeding remain underexplored. In this study, we tested the prediction that relative losses of foliage to defoliating insects increase with leaf damage diversity (LDD), and we also explored the mechanisms underlying the observed LDD patterns. We measured insect herbivory in 501 individuals of three deciduous woody species (Betula pubescens, Salix phylicifolia, and Vaccinium uliginosum) across 38 localities in north-western Russia, collected 8844 leaves damaged by defoliating insects, classifying the 21,073 feeding events observed in these leaves into 29 damage types. Overall, LDD significantly decreased with increasing latitude but showed no variation along elevation or pollution gradients. Herbivory weakly but significantly increased with increasing LDD, and a strong positive correlation between the rarefied number of leaf damage types and their evenness provided evidence for the complementarity effect underlying this herbivory increase, indicating that insects producing different leaf damage types differ in their resource use. Full article

Understanding plant tolerance to defoliation is crucial for sustainable pest management and reducing pesticide use in food production. This study explores quinoa’s (Chenopodium quinoa Willd.) responses to foliar damage, which have been largely unexamined. Over two seasons, quinoa plants were subjected to mechanical defoliation at different pre-reproductive stages and intensities (0–60%) in the first season, and both mechanical and insect-induced (Trichoplusia ni (Hübner), Lepidoptera: Noctuidae) defoliation in the second. The results showed that quinoa plants consistently tolerated defoliation without reductions in grain number, weight, above-ground biomass, or harvest index. These compensatory responses were independent of the defoliation method, timing, or intensity. In the first season, overcompensatory effects were observed, leading to increased plant biomass at 60% early defoliation and 40% late defoliation. Additionally, early defoliation at 20% and 60%, as well as late defoliation at 60%, led to an increase in grain number without affecting grain weight. Defoliation did not significantly alter the phenolic content, sapogenins, or antioxidant capacity of the grains, preserving their phytochemical quality. These findings enhance the understanding of quinoa’s resilience to herbivory, suggesting that it can withstand defoliation stress without compromising yield or quality. Full article