Wood Decay Research Articles

Biological control of some wood-decay fungi with antagonistic fungi.

One of the most important biological factors that damage wood materials are wood-decay fungi (WDF). Chemical preservatives have traditionally been the most effective method for controlling WDF. However, due to environmental pressures, scientists are working on alternative protection methods. The aim of this study was to investigate the potential of some antagonistic fungi against wood-decay fungi as a biological control agent (BCA). For this purpose, the antagonistic effects of Trichoderma harzianum, Trichoderma viride, Aspergillus niger, and Penicillium brevicompactum fungi were investigated against the Trametes versicolor, Trametes hirsuta, Stereum hirsutum, Coniophora puteana, Neolentinus lepideus, and Postia placenta species of wood-decay Basidiomycetes fungi. In the study, firstly, inhibition rates were determined by comparing dual culture tests on agar medium, and then the performance of BCAs was compared by performing decay tests on wood blocks. As a result of the study, it was determined that the species belonging to the genus Trichoderma showed a very effective performance on WDF, increased the inhibition rate to 76-99%, and reduced the weight loss to 1.9-5.8%. Considering the inhibition rates, it was determined that the most effective rate of the BCAs was on P. placenta and the least on S. hirsutum species. According to the results obtained, it has been determined that some BCAs were very effective biological control agents of rot fungi on agar and wood blocks in vitro. However, in order to more clearly determine the effectiveness of BCAs in practice, this study, which was carried out in the laboratory environment, should be supported by tests performed in contact with the external field and soil.

Simultaneous Hydrodistillation of Cedrus atlantica Manetti and Salvia rosmarinus Spenn: Optimization of Anti-Wood-Decay Fungal Activity Using Mixture Design Methodology.

Chemical fungicides are often harmful to people and the environment because of their toxicity. The wood protection industry places a high priority on replacing them with natural products. Therefore, this investigation focused on developing a formulation of a binary combination of Salvia rosmarinus Spenn and Cedrus atlantica Manetti obtained by Simultaneous hydrodistillation to protect the wood from decay using a mixture design methodology. The chemical composition of essential oil was identified by gas chromatography coupled with mass spectrometry (GC/MS), and their anti-wood-decay fungal activity was assessed using the macrodilution method against four fungi responsible for wood decay: Coniophora puteana, Coriolus versicolor, Gloeophyllum trabeum, and Poria placenta. The results of GC/MS identified myrtenal as a new component appearing in all binary combinations. The optimum anti-wood-decay fungal activity was observed in a combination of 60% S. rosmarinus and 40% C. atlantica essential oils, providing an effective concentration for 50% of maximal effect (EC50) value of 9.91 ± 1.91 and 9.28 ± 1.55 μg/mL for C. puteana and C. versicolor, respectively. The highest anti-wood-decay fungal activity for G. trabeum and P. placenta was found in the combination of 55% of S. rosmarinus and 45% of C. atlantica essential oils, with EC50 values of 11.48 ± 3.73 and 22.619 ± 3.79 μg/mL, respectively. Combined simultaneous hydrodistillation improved the antifungal effect of these essential oils. These results could be used to improve antifungal activity and protect wood against wood-decay fungi.

Wood Coloration and Decay Capabilities of Mycoparasite Scytalidium ganodermophthorum.

Scytalidium ganodermophthorum (telomorph: Xylogone ganodermopthora) Kang, Sigler, Lee & Yun is a destructive fungal pathogen that produces a yellow pigment that is used in sustainable product development. Similar pigmenting ascomycetes cause soft rot in woody substrates, however, the decay capabilities of S. ganodermophthorum have not been assessed or related to pigment production. A wood block decay test showed highly variable production of the expected bright yellow pigment and a secondary darker pigment when tested against multiple wood species and nutrient conditions. Microscopic examination showed cell wall erosion typical of type-2 soft rot in wood, although enzymatic analysis did not show detectible levels of endocellulase. Chitinase was detected in plate cultures but not wood cultures, indicating adaption of the fungus to a variety of environmental growth conditions. The high variability of pigmentation in wood cultures suggests that growth of S. ganodermophthorum on liquid media and use of extracted pigment is a superior method for obtaining consistent yellow coloration.

Innovative, low-cost eco-composite boards produced from high-energy milled wood, plastic waste, and bio-polymer

Currently, there is a big issue with waste, its processing and subsequent use. While there are many initiatives to replace materials that are poorly biodegradable, it is necessary to process and ideally use the waste that is already produced. In this study, the properties of composite boards made of waste materials and biodegradable polymer were investigated. The composite boards were made from wood and plastic waste using high-energy milling technology. This technology for material preparation is promising, as it includes controlling the morphology of particles, homogenizing the mixture, and drying the material during the milling process. The results showed higher flexural strength of high-density fiberboard (HDF) boards compared with tested composites with one exception. Wood/poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [PHBV] composite exhibited 30% higher modulus of elasticity (MOE) than HDF due to the higher modulus of PHBV. The lowest thickness swelling (3%) and water absorption (12%) were measured for wood/recycled high density polythene (rHDPE) composite. The HDF boards recorded the lowest dimensional stability. The highest water absorption of tested composites was measured for wood/PHBV composite. The resistance to wood-rotting fungi was greatest for wood/PHBV composite containing marble powder, which corresponded to the results of scanning electron microscopy.

Structural and functional microbial diversity in deadwood respond to decomposition dynamics.

We investigated the changes in microbial community diversities and functions in natural downed wood at different decay stages in a natural oak forest in the Italian Alps, through metagenomics analysis and in vitro analysis. Alfa diversity of bacterial communities was affected by the decay stage and log characteristics, while beta diversity was mainly driven by log diameter. Fungal and archaeal beta diversities were affected by the size of the sampled wood (log diameter), although, fungi were prominently driven by wood decay stage. The analysis of genes targeting cell wall degradation revealed higher abundances of cellulose and pectin-degrading enzymes in bacteria, while in fungi the enzymes targeting cellulose and hemicellulose were more abundant. The decay class affected the abundance of single enzymes, revealing a shift in complex hydrocarbons degradation pathways along the decay process. Moreover, we found that the genes related to Coenzyme M biosynthesis to be the most abundant especially at early stages of wood decomposition while the overall methanogenesis did not seem to be influenced by the decay stage. Intra- and inter-kingdom interactions between bacteria and fungi revealed complex pattern of community structure in response to decay stage possibly reflecting both direct and indirect interactions.

Qualitative metabolomics-based characterization of a phenolic UDP-xylosyltransferase with a broad substrate spectrum from Lentinus brumalis

Wood-decaying fungi are the major decomposers of plant litter. Heavy sequencing efforts on genomes of wood-decaying fungi have recently been made due to the interest in their lignocellulolytic enzymes; however, most parts of their proteomes remain uncharted. We hypothesized that wood-decaying fungi would possess promiscuous enzymes for detoxifying antifungal phytochemicals remaining in the dead plant bodies, which can be useful biocatalysts. We designed a computational mass spectrometry-based untargeted metabolomics pipeline for the phenotyping of biotransformation and applied it to 264 fungal cultures supplemented with antifungal plant phenolics. The analysis identified the occurrence of diverse reactivities by the tested fungal species. Among those, we focused on O-xylosylation of multiple phenolics by one of the species tested, Lentinus brumalis. By integrating the metabolic phenotyping results with publicly available genome sequences and transcriptome analysis, a UDP-glycosyltransferase designated UGT66A1 was identified and validated as an enzyme catalyzing O-xylosylation with broad substrate specificity. We anticipate that our analytical workflow will accelerate the further characterization of fungal enzymes as promising biocatalysts.

Efficient Aflatoxin B1 degradation by a novel isolate, Pseudomonas aeruginosa M-4

Aflatoxin B1 (AFB1) is the most common mycotoxin with the highest toxicity, posing a threat for food contamination. In this study, the bacterium Pseudomonas aeruginosa M-4 was isolated from rotten wood, and its culture supernatant showed a 56.79% AFB1 degradation rate. Treatment with proteinase K, sodium dodecyl sulfate, and trichloroacetic acid decreased the AFB1 degradation rate in the culture supernatant to 20.71%, 10.83%, and 19.62%, respectively. Moreover, heating the culture supernatant at 121 °C for 30 min increased in the AFB1 degradation rate to 84.76%, indicating effective degradation by heat-resistant and inducible extracellular proteins or enzymes. P. aeruginosa M-4 reduced the content of AFB1 in contaminated maize (90.57%, 14 d). Additionally, high-performance liquid chromatography and ultra-high-performance liquid chromatography-quadrupole time-of-flight mass spectrometry analyses showed that AFB1 was biotransformed into structurally different compounds, (C17H16O6), (C16H14O5), (C17H14O5), and (C16H10O6). According to the structure-activity relationship, these degradation products were produced by the destruction of partial toxic sites of AFB1, so the toxicity of these products may be lower than that of AFB1. Thus, P. aeruginosa M-4 has excellent potential for application in the detoxification of AFB1 in food and feed.

Phylogenetic analysis and morphology of Ganoderma multipileum, a Ganoderma species associated with dieback of the metropolitan woody plant Delonix regia (Boj. ex Hook.) Raf. in Vietnam.

Ganoderma multipileum, a wood decay mushroom, was initially discovered and classified in Taiwan through the analysis of its morphology and the internal transcribed spacer (ITS) region of nuclear ribosomal DNA. In this study, we identified a mushroom associated with the dieback of Delonix regia (Boj. ex Hook.) Raf., a woody ornamental street tree in Vietnam, as Ganoderma multipileum. This classification was based on phylogenetic analysis of ITS, RPB2, and TEF1 sequences, as well as morphology assessment and scanning electron microscope observation of basidiospores. The phylogenetic analysis revealed that the specimens collected in Vietnam formed a monophyletic group of Ganoderma multipileum with a high bootstrap value and posterior probability (100%/1.00). Furthermore, the morphological features consistent with laccate Ganoderma, including a thin pileipellis composed of enlarged and bulbous hyphae, and the basidiomes exhibited two different phenotypes. Notably, scanning electron microscopy of the basidiospores revealed ovoid spores with numerous echinules, providing the first documented evidence of this characteristic for Ganoderma multipileum. This research represents the first recorded instance of Ganoderma multipileum in Vietnam associated with the dieback of Delonix regia.

AKTIVITAS ANTIJAMUR PELAPUK KAYU NANOPARTIKEL KITOSAN-EKSTRAK N-HEKSAN DAGING BUAH KAYU GADIS (Cinnamomum parthenoxylon)

This study aims to synthesize chitosan nanoparticles - n-hexane extract of Cinnamomum parthenoxylon (CP) fruit using the ionic gelation method, to characterize them, and to determine their antifungal activity against the wood-rotting fungi Trametes versicolor and Fomitopsis palustris. Chitosan-CP extract nanoparticles were formulated with chitosan:Na-TPP:CP extract ratio of 1:1:0.5. Particle size and polydispersity index were determined using a particle size analyzer (PSA), and particles morphology was observed using a scanning electron microscope (SEM), and antifungal activity was measured using agar media. The results revealed that the average size of chitosan nanoparticles (base) was 276.9 nm, while the average size of chitosan-CP extract nanoparticles was 807.6 nm. The polydispersity index (PI) of both nanoparticles was greater than 0.7. Observations of the nanoparticles' morphology revealed that aggregation/agglomeration formed in the resulting particles. Both nanoparticles chitosan (base) and chitosan-CP extract inhibited the growth of white rot fungi (T. versicolor) more than brown rot fungi (F. palustris), as measured by the inhibitory zone.

Shift in fungal communities associated with Pinus sylvestris stands affected by root rot

Introduction
 Scots pine (Pinus sylvestris) covers large areas in European regions with significant economic importance to Ukrainian forest industry. Root rot caused by the wood-decay fungus Heterobasidion annosum damages both below- and above-ground parts of Scots pines. The disease progress is likely to be affected by reshaping in the forest such as soil properties, vegetation composition, and tree age. These changes are apparently followed up by paralleled shifts in fungal community composition on forest soil with potential feedback on ecosystem functioning.
 The objective of the study was to screen fungal groups associated with the root system of P. sylvestris in stands affected by H.annosum s.s. to better understand the pathogenesis and development of root rot infection, as well as to recognize whether root size and disease severity affect diversity of fungi of the root system in the forest-steppe conditions of Ukraine. The additional object was to study other resident microflora of P. sylvestris root infested by H.annosum s.s. to find out whether the H. annosum s.s. impacts the overall diversity of other fungi.
 Materials and Methods
 The field study was carried out in 2018–2020. Field study sites were pure pine forest stands located in Kharkiv region (compartment 126, subcompartment 7, tract Bugri, Kharkiv Forest Research Station). Wood core and root samples from P. sylvestris were collected from the five infected (50–100 m apart from each other) and five non-infected trees (up to 500 m apart from the infested area and 50–100 m apart from each other). Wood and root samples were used for fungal culturing and direct sequencing using ITS1F and ITS4 primers.
 Results
 In the present study, we tried to evaluate fungal communities across diseased Pinus sylvestris stands and investigated correlations between taxonomic composition and forest health. Not surprisingly, root rot infestation had a significant effect on root-associated fungal abundance and diversity. During disease development, the root-associated fungal community shifted in composition from dominance by saprotrophic fungi to ectomycorrhizal and pathogenic fungal species. Our results suggested that maintenance of functional diversity in the root-associated fungal community may sustain long-term forest health or even root rot resistance to some extent by retaining a capacity for symbiosis-driven recycling of organic nutrients; however, this hypothesis is necessary to carefully examine and prove further.
 Conclusions
 Fungal culturing from 10 surface-sterilized wood cores resulted in 21 fungal cultures, 2.1 per wood segment. Direct sequencing from 40 surface-sterilized segments of lateral roots resulted in 247 fungal sequences or 6.2 per root segment on average. The most dominant fungi from the infested trees of Pinus sylvestris were Dactylonectria macrodidyma (4.98%), Acremonium sp (4.52%), Cladosporium cladosporioides (4.07%) from Ascomycota and Heterobasidion annosum s.s. (4.07%) from Basidiomycota, while for non-infested group Unidentified Ascomycota175244 (13.19%), Penicillium spinulosum (9.89%), Acremonium sp. (8.79%), Bionectriaceae sp. (8.79%) were the most common.
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Wood-Decay Fungi Fructifying in Mediterranean Deciduous Oak Forests: A Community Composition, Richness and Productivity Study

Deadwood is involved in several important ecological roles, being the fundamental habitat of wood-decay fungi. At the same time, this polyphyletic group of fungi is the principal agent of wood decomposition, regulating the carbon cycle and the food resource for many other organisms. It is known that the diversity and community composition of wood-decay fungi are related to the tree species, decay stage and size of the woody debris in which they are living. Nevertheless, there is a lack of information on Mediterranean Quercus cerris L. forests. In response, we explored how wood-decay fungi colonize different woody types and how the productivity, richness and community composition of these fungi is influenced by the decay stage and size of the deadwood. Our results indicate that the studied groups, i.e., Ascomycetes, Corticioids, Polyporoids and Heterobasidiomycetes responded differently to the woody debris classes. Moreover, we note the high importance of smaller and soft-decayed woody debris for community composition and richness, hosting a great number of species, in addition to the positive effect of the heterogeneity of the woody debris size for wood-decay fungi productivity.

α-Diversity of plant communities, forest birds and wood-decaying fungi in urban parks of a metropolis

The biodiversity of urban parks is an indicator object of monitoring biodiversity under conditions of constant recreational pressure. The main approaches to these issues are based on measuring the indices of vertical and horizontal heterogeneity of parklands, which make it possible to identify links between plant, wood-decaying fungi and bird diversities. As in the case of Kyiv, Ukraine, we augmented existing published data with new compositions, links and α-diversity indices of plant, fungi and bird communities in the parks of a metropolis! The infraction of α-diversity (diversity, dominance, and evenness indices) and the compositions in the communities depending on the level of recreational transformation of the parks were established. The main driving factors of α-diversity in urban parks were shown. Further research is needed to use these relationships to indicate the state of park ecosystems.Keywords: plant, vegetation; forest birds; wood-decaying fungi; recreational impact; diversity index, dominance index, evenness index

NMR-Based Characterization of Wood Decay Fungi as Promising Novel Foods: Abortiporus biennis, Fomitopsis iberica and Stereum hirsutum Mycelia as Case Studies

Wood Decay Fungi (WDF) are fungi specialized in degrading wood. An interesting perspective is their use as a source of Novel Foods or food ingredients. Here, for the first time, the metabolite profiling of hydroalcoholic and organic extracts from A. biennis, F. iberica, S. hirsutum mycelia was investigated by NMR methodology. Amino acids (alanine, arginine, asparagine, aspartate, betaine, GABA, glutamate, glutamine, histidine, isoleucine, leucine, lysine, phenylalanine, threonine, tryptophan, tyrosine, valine), sugars (galactose, glucose, maltose, trehalose, mannitol), organic acids (acetate, citrate, formate, fumarate, lactate, malate, succinate), adenosine, choline, uracil and uridine were identified and quantified in the hydroalcoholic extracts, whereas the 1H spectra of organic extracts showed the presence of saturated, mono-unsaturated and di-unsaturated fatty chains, ergosterol,1,2-diacyl-sn-glycero-3-phosphatidylethanolamine, and 1,2-diacyl-sasglycero-3-phosphatidylcholine. A. biennis extracts showed the highest amino acid concentration. Some compounds were detected only in specific species: betaine and mannitol in S. hirsutum, maltose in A. biennis, galactose in F. iberica, GABA in F. iberica and S. hirsutum, and acetate in A. biennis and S. hirsutum. S. hirsutum showed the highest saturated fatty chain concentration, whereas DUFA reached the highest concentration in A. biennis. A high amount of ergosterol was measured both in A. biennis and F. iberica. The reported results can be useful in the development of WDF-based products with a high nutritional and nutraceutical value.

Aerobic H2 production related to formate metabolism in white-rot fungi.

Biohydrogen is mainly produced by anaerobic bacteria, anaerobic fungi, and algae under anaerobic conditions. In higher eukaryotes, it is thought that molecular hydrogen (H2) functions as a signaling molecule for physiological processes such as stress responses. Here, it is demonstrated that white-rot fungi produce H2 during wood decay. The white-rot fungus Trametes versicolor produces H2 from wood under aerobic conditions, and H2 production is completely suppressed under hypoxic conditions. Additionally, oxalate and formate supplementation of the wood culture increased the level of H2 evolution. RNA-seq analyses revealed that T. versicolor oxalate production from the TCA/glyoxylate cycle was down-regulated, and conversely, genes encoding oxalate and formate metabolism enzymes were up-regulated. Although the involvement in H2 production of a gene annotated as an iron hydrogenase was uncertain, the results of organic acid supplementation, gene expression, and self-recombination experiments strongly suggest that formate metabolism plays a role in the mechanism of H2 production by this fungus. It is expected that this novel finding of aerobic H2 production from wood biomass by a white-rot fungus will open new fields in biohydrogen research.

Addition of Some Wood Rotting Polypores from Satara District (M.S).

Addition of Some Wood Rotting Polypores from Satara District (M.S).

Construction of white-rot fungal-bacterial consortia with improved ligninolytic properties and stable bacterial community structure

It is believed that wood-rot fungi change their wood decay activities due to influences from co-existing bacterial communities; however, it is difficult to elucidate experimentally the interaction mechanisms in fungal-bacterial consortia because the bacterial community structure is quite unstable and readily changes. Indeed, the wood decay properties of fungal-bacterial consortia consisting of a white-rot fungus Phanerochaete sordida YK-624 and a natural bacterial community changed dramatically during several sub-cultivations on wood. Therefore, development of a sub-cultivation method that imparts stability to the bacterial community structure and fungal phenotype was attempted. The adopted method using agar medium enabled maintenance of fungal phenotypes relating to wood decay and the bacterial community even through dozens of repetitive sub-cultures. Some bacterial metabolic pathways identified based on gene predictions were screened as candidates involved in P. sordida–bacterial interactions. In particular, pathways related to prenyl naphthoquinone biosynthesis appeared to be involved in an interaction that promotes higher lignin degradation selectivity by the consortia, as naphthoquinone derivatives induced phenol-oxidizing activity. Based on these results, it is expected that detailed analyses of the relationship between the wood-degrading properties of white-rot fungal-bacterial consortia and bacterial community structures will be feasible using the sub-cultivation method developed in this study.

Fine-scale cation dynamics and control by Rhodonia placenta and Pleurotus ostreatus during wood decay

Fungi are the primary decomposers of wood across the globe. They redistribute the vast pool of wood carbon to other parts of the carbon cycle using mechanisms that also have intriguing potential in bioconversion and biotechnology applications. To make a living in the relatively sparse microenvironment of wood, these filamentous fungi must import many of their needs, including cations. Understanding the timing of cation import can help us validate the functions of cations in wood decay and create a clearer understanding of these complex wood degradation mechanisms. In this study, we resolved cation timing dynamics across space for two fungi (brown rot fungus Rhodonia placenta and white rot fungus Pleurotus ostreatus) using a wood wafer system. We found some expected patterns of the cation dynamics for both fungi, and a clear role for iron at the early stages of brown rot decay. On the other hand, the lack of an increase in manganese during initial white rot decay was surprising. Unexpectedly, we also saw a spike in copper during early brown rot decay that demands more investigation as a potential player in the brown rot mechanism.

Energy value of silver fir (Abies alba) and Norway spruce (Picea abies) wood depending on the degree of its decomposition by selected fungal species

Negative environmental impacts related to climate change and social pressure to raise the rotation age of forests contribute to the quality deterioration of harvested wood, including its decomposition by fungi. This paper presents the results of laboratory experiments investigating the decomposition of Norway spruce (Abies alba) and silver fir (Picea abies) wood by selected species of decay fungi: Hericium flagellum and Bondarzewia mesenterica (causing white rot) as well as Rhodofomes roseus (causing brown rot). The decay process affects wood density, elemental composition, net calorific value, as well as the amount and price of the energy contained in the wood. Wood density was measured conventionally using an electronic caliper and laboratory balance. Energy parameters were determined using elemental analyzer and combustion calorimeter. Wood decay was found to adversely affect energy content per unit of wood at a given volume, thus leading to higher prices per unit of energy. Over the 120 days of the experiment, wood parameters were not affected considerably by Hericium flagellum or Bondarzewia mesenterica. Of the three examined fungal species, Rhodofomes roseus caused the highest weight loss of wood and the greatest decrease in its oven-dry density (spruce - a decrease from 409 to 214 kg m−3; fir - a decrease from 420 to 306 kg m−3), unfavorably reducing energy content per 1 m3 of wood (spruce – decrease by 3.8 GJ m−3; fir – decrease by 2.3 GJ m−3) and raising the unit price of energy.

Creating a partial 3D model in selected biological areas using a small number of photographs

Currently, we are registering a great boom in computer technology, which allows us to use ICT techniques and procedures even in those areas in which it was not common. One such area is the creation of partial or complete realistic 3D models of real bodies in biology - in our case, trees or wood. Their great advantage is that they can capture various cases of growth deformations, interesting shapes or atypical formations. Many are temporary and unstable. An example can be a wood rotting fungus. These can then be studied outside the place of their growth and at the same time preserved for future comparisons. This leads to another possibility of their use in the educational process. We must also point out that a real 3D model with preserved dimensional proportions and true colors is a much better solution for studying than a classic photograph. We use photogrammetry to create 3D models. Its great advantage is that the 3D model is created from a series of photos that capture the part of the real object from which we want to create a partial 3D model. A classic touchscreen mobile phone is enough to get these photos. However, many problems and complications are associated with the creation of 3D models. It is not always possible to get quality photos. This can be caused by e.g. height, terrain or other obstacles. To obtain the desired partial 3D model, it is ideal if several conditions are met when obtaining photos, such as overlapping photos, sharpness, color, visible texture, etc. But in real cases it is not always possible to achieve this and therefore in our contribution we focus on the subsequent processing by which we can achieve our goal - even under the aforementioned unfavorable conditions to create a 3D model.

First Report of the Armillaria Root Disease Pathogen, Armillaria solidipes, on Black Oak (Quercus velutina) in North Carolina, USA.

Armillaria root disease is among the largest causes of mortality and lost productivity of widely ranging horticultural, urban, and forest trees/shrubs in diverse boreal, temperate, and tropical regions around the world (Kim et al. 2022). Damage from Armillaria root disease will likely increase in response to changing climate and extreme weather because environmental stress can predispose host trees to Armillaria root disease (Murray and Leslie 2021; Kim et al. 2021). On August 14, 2021, a mature black oak (Quercus velutina) ca. 29 m in height and 64 cm DBH experienced a complete structural failure originating at the root plate, falling onto a major highway within the Pisgah National Forest near Brevard, North Carolina (35°16'50.876"N, 82°42'51.785"W, elevation 680 m) during sunny, calm conditions. No above-ground indications of predisposing disturbance, injury, or insect/disease activity were observed. Advanced wood decay, however, was present in many structural roots of the exposed root plate; abundant rhizomorphs attached to the surfaces of most roots were noted (Supplemental Figure 1). One large primary root (ca. 23 cm in diameter) exhibited clear signs of Armillaria root disease at the point of failure as evidenced by an extensive decay column, abundant black rhizomorphs on the root surface, and white mycelial fans (a sign of pathogenicity) within the root itself (Supplemental Figure 1). Rhizomorph samples were established in culture, two Armillaria isolates (PNF#001R-1 and PNF#001R-2) were examined, and pairing tests showed that both isolates belonged to the same genet (PNF#001R-1 = PNF#001R-2). Based on translation elongation factor 1α (tef1) sequences, both isolates (one genet) were identified as A. solidipes (GenBank accession no. OP823701), showing 98% similarity with A. solidipes tef1 sequences (e.g., MH879015) in GenBank. Also, nine replications of somatic incompatibility tests of the isolate with five North American Armillaria spp. [A. solidipes, A. mellea, A. gallica, A. mexicana, and Desarmillaria caespitosa (= North American A. tabescens)] showed 67% compatibility with A. solidipes, compared with 0-22% for A. mellea, D. caespitosa, A. gallica, and A. mexicana. All test species but A. mexicana are reported to occur in the eastern and/or southern USA, while A. mexicana occurs in a similar environment in Mexico (Elías-Román et al. 2018). To our knowledge, this is the first confirmed report of A. solidipes in North Carolina, USA, where it was causing disease on black oak, and this is the most southerly confirmed case of A. solidipes in eastern North America. Although Armillaria inoculation tests are impractical, black oak was previously reported as a host of A. solidipes in Massachusetts, USA (Brazee and Wick 2009). Armillaria solidipes is considered as the most important Armillaria root disease pathogen of conifer forests in western USA (Lockman and Kearns 2016), but it has been suggested that A. solidipes can thrive in northern hardwood forests that reside near conifer forests (Brazee and Wick 2009). Climate change is predicted to increase damage caused by A. solidipes on conifers in the western USA (Kim et al. 2021); however, it is undetermined if the occurrence of A. solidipes-caused disease in North Carolina is related to climate change or how climate change could influence this disease across the region. More surveys are needed to assess the impact of Armillaria root disease on health of mixed forests in the eastern USA.