Blue-stain Fungi Research Articles

Susceptibility of thermo-hydro-treated birch plywood to mould and blue stain fungi

ABSTRACTIn this study, mould and blue stain susceptibility, capillary water uptake (CWU) and microstructural properties of two thermo-hydro-treated (THT) birch plywood products A and B were investigated. Plywood A represented a THT industrial plywood glued with a phenol formaldehyde (PF) adhesive. Plywood B represented panels from THT veneers glued with a PF film. The THT regimes were (temperature, °C/time, min): 150/10, 150/50, 160/10 and 160/50. Both THT plywood products and untreated samples were resistant to mould and blue stain growth in 1 month of exposure in laboratory and outdoor conditions. A statistically significant correlation between fungal growth in laboratory and outdoor conditions for plywood products A and B was not found (P > .05). Artificial weathering of both plywood products provided adverse fungal growth results compared to the natural weathering test outdoors. The fungal growth on plywood A and B samples mutually strongly correlated (P < .05) only in the outdoor test. Plywood B samples demonstrated a much lower CWU than plywood A, obviously because of microstructural changes, including densification, and type of glue used. Lower CWU of THT plywood in comparison with untreated samples did not provide clear evidence on inhibition of fungal growth.

Chiral ionic liquids with a (−)-menthol component as wood preservatives

Abstract Research has been conducted on the biotic activity of eight chiral ionic liquids (CILs) with a natural component in the form of (−)-menthol with the configuration (1R,2S,5R) against Basidiomycetes and Fungi imperfecti. Optically active imidazolium salts were tested as follows: several asymmetric 3-alkyl-1-[(1R,2S,5R)-(−)-menthoxymethyl]imidazolium chlorides with various alkyl substituents (from methyl to dodecyl) and one symmetric 1,3-bis[(1R,2S,5R)-(−)-menthoxymethyl]imidazolium chloride containing two (1R,2S,5R)-(−)-menthol substituents. Mycological tests were carried out with brown-rot and white-rot fungi, as well as with filamentous fungi, i.e. mold fungi and blue stain fungi. The new, optically active compounds demonstrated diverse effectiveness of fungicidal activity, which was dependent on the chemical structure of the functional groups. The natural (−)-menthol component, introduced as a substituent in ionic liquids, turned out to be an optically active compound with activity against wood-destroying fungi. (1R,2S,5R)-(−)-menthol was especially active against the fungi tested. The fungicidal value of imidazolium chloride with two (−)-menthol substituents against Coniophora puteana ranged from 1.8 to 2.9 kg m−3. The adsorption processes on Scots pine wood and resistance to water leaching were examined. The sorption properties of symmetric salts with two optical active (−)-menthol substituents fitted very well with the Freundlich adsorption model. Attenuated total reflection-infrared (ATR-IR) spectra confirmed that methylene groups of the aliphatic substituent, the ring of the heterocyclic imidazole, as well as the ether bridge of the natural (−)-menthol component were fixed in the structure of the impregnated pine wood (Pinus sylvestris L.). The positive results encourage further investigation of the potential application of novel functional CILs (Figure 1) for wood protection.

Genetic and genomic evidence of niche partitioning and adaptive radiation in mountain pine beetle fungal symbionts

Bark beetles form multipartite symbiotic associations with blue stain fungi (Ophiostomatales, Ascomycota). These fungal symbionts play an important role during the beetle's life cycle by providing nutritional supplementation, overcoming tree defences and modifying host tissues to favour brood development. The maintenance of stable multipartite symbioses with seemingly less competitive symbionts in similar habitats is of fundamental interest to ecology and evolution. We tested the hypothesis that the coexistence of three fungal species associated with the mountain pine beetle is the result of niche partitioning and adaptive radiation using SNP genotyping coupled with genotype-environment association analysis and phenotypic characterization of growth rate under different temperatures. We found that genetic variation and population structure within each species is best explained by distinct spatial and environmental variables. We observed both common (temperature seasonality and the host species) and distinct (drought, cold stress, precipitation) environmental and spatial factors that shaped the genomes of these fungi resulting in contrasting outcomes. Phenotypic intraspecific variations in Grosmannia clavigera and Leptographium longiclavatum, together with high heritability, suggest potential for adaptive selection in these species. By contrast, Ophiostoma montium displayed narrower intraspecific variation but greater tolerance to extreme high temperatures. Our study highlights unique phenotypic and genotypic characteristics in these symbionts that are consistent with our hypothesis. By maintaining this multipartite relationship, the bark beetles have a greater likelihood of obtaining the benefits afforded by the fungi and reduce the risk of being left aposymbiotic. Complementarity among species could facilitate colonization of new habitats and survival under adverse conditions.

Siloxane-treated and copper-plasma-coated wood: Resistance to the blue stain fungus Aureobasidium pullulans and the termite Reticulitermes flavipes

Scots pine (Pinus sylvestris L.) sapwood specimens were subjected to a two-step treatment combining vacuum-pressure impregnation with short-chain siloxanes followed by copper deposition on the wood surface via atmospheric pressure plasma. The obtained materials were exposed to a blue stain fungus in a laboratory test following EN 152 (2011). Copper treatment alone reduced fungal colonisation, but did not fully prevent it. A two-step treatment was able to impart high resistance to Aureobasidium pullulans. Termite resistance of siloxane-treated and copper-plasma coated wood was also assessed. A laboratory no-choice test according to EN 118 (2013) revealed strong attack by Reticulitermes flavipes, but termite mortality increased compared to untreated wood. In contrast, under choice conditions, R. flavipes exhibited significant avoidance towards the treated specimens.

The effect of natural weathering on untreated wood surface

As a result of contemporary ecological and sustainable movements, a number of constructions from wood, as the only renewable building material, is still increasing. In accordance with these trends, wood elements are often left untreated. The presented study is aimed to characterize and compare a surface degradation of untreated wood caused by weathering. Weathering characteristics of softwoods and hardwoods (spruce, pine, Douglas fir, larch, oak, black locust, maple, poplar and alder) during twelve months of exposure in the climatic conditions of Central Europe were determined. All the wood species were characterized by colour and gloss changes and increasing roughness. The lowest discoloration was observed for oak and the highest one for spruce wood, respectively. The lowest changes of roughness were observed for alder, the highest for spruce wood. The depth of colour changes was relatively similar among the softwoods. Regarding hardwoods, it varied more. The values of total colour changes had a significant correlation with the depth values of these colour changes. Maple, alder and poplar samples were characterized by the presence of mould and blue-stain fungi. Douglas fir wood was found to be the most liable for the formation of cracks.

Defence reactions of mature Norway spruce (Picea abies) before and after inoculation of the blue-stain fungus Endoconidiophora polonica in a drought stress experiment

Abstract We performed an inoculation experiment using the blue-stain fungus Endoconidiophora polonica at the Rosalia Roof study site, which was set up to study drought effects on Norway spruce susceptibility to attacks by the European spruce bark beetle Ips typographus. Tree resistance parameters such as resin flow rate and extent of hypersensitive wound reaction in the phloem were investigated prior to and after fungal infection. Sample trees with different drought treatments (trees fully covered or semi-covered by roofs, control trees) were inoculated with E. polonica in July 2014. In order to check for areas of phloem necrosis, the outer bark around the inoculation holes was scratched off 6 weeks later. We recorded the amount of resin exudation within 12 hours overnight in August and September 2013 and 2014. Although wound reaction zones did not differ in size between tree collectives of the various treatments, fully covered trees tended to exhibit larger necrotic areas compared to control trees. The least water supplied trees showed lowest resin flow rates prior to fungal inoculation, but were the only group to show significantly enhanced resin flow five weeks after the evaluation of defence reactions. Our results agree with earlier findings that wounding and few fungal inoculations can increase tree resistance in the medium term given not too severe water stress. Further investigations will clarify how water stress affects the availability of non-structural carbohydrates for secondary metabolism, when depletion of resources eventually occurs, and at which point trees are most susceptible to bark beetle attack.

Inoculation of ophiostomatoid fungi in loblolly pine trees increases the presence of subterranean termites in fungal lesions

Many bluestain (ophiostomatoid) fungi are inoculated into trees via bark beetle activity, but their ecological roles are not fully understood, particularly for interactions with invertebrates outside bark beetle and phoretic mite associations. Recently, correlational field studies and small-scale laboratory feeding trials have demonstrated subterranean termites have increased presence on and preferential feeding of bluestain-infected wood, but experimental field evidence is lacking. To test the hypothesis that bluestain fungi increase termite presence in infected trees, we inoculated 72 loblolly pine trees in the southeastern USA with one of four bluestain fungi (Ophiostoma minus, O. ips, Leptographium terebrantis, L. procerum), a combination (O. minus + L. terebrantis), or H2O as a control. Over four years, all fungi-inoculated trees formed lesions around injection sites, while control trees formed no lesions except for two contaminated control trees that were excluded from analyses. Bluestain-inoculated trees had increased termite presence in and around fungal lesions, whereas control trees had no termites present. Specifically, termites were present on 35 % of fungi-inoculated trees, presence was consistent over time, and there was no difference among fungal species. This study experimentally demonstrates a link between bluestain fungi and subterranean termites in forests, which could impact tree dynamics post-bluestain infection.

The great spruce bark beetle (Dendroctonus micans Kug.) (Coleoptera: Scolytidae) in Lithuania: occurrence, phenology, morphology and communities of associated fungi.

We studied the occurrence, morphology and phenology of Dendroctonus micans in Lithuania and the fungi associated with the beetle at different developmental stages. The occurrence of D. micans was assessed in 19 seed orchards (at least 40 years old) of Picea abies (L. Karst.) situated in different parts of the country. Bark beetle phenology was studied in two sites: a seed orchard of P. abies and a plantation of Picea pungens (Engelm.). D. micans morphology was assessed under the dissection microscope using individuals at different developmental stages that were sampled during phenology observations. Communities of fungi associated with D. micans were studied using both fungal culturing methods and direct high-throughput sequencing from D. micans. Results showed that the incidence D. micans was relatively rare and D. micans was mainly detected in central and eastern Lithuania. The life cycle included the following stages: adult, egg, I-V developmental stage larvae and pupa. However, development of D. micans was quicker and its nests larger under the bark of P. pungens than of P. abies, indicating the effect of the host species. Fungal culturing and direct high-throughput sequencing revealed that D. micans associated fungi communities were species rich and dominated by yeasts from a class Saccharomycetes. In total, 319 fungal taxa were sequenced, among which Peterozyma toletana (37.5% of all fungal sequences), Yamadazyma scolyti (30.0%) and Kuraishia capsulate (17.7%) were the most common. Plant pathogens and blue stain fungi were also detected suggesting their potentially negative effects to both tree health and timber quality.

Influence of Artificial and Natural Weathering on the Moisture Dynamic of Wood

Wood that is used in outdoor applications is frequently exposed to weathering and is thus prone to fungal degradation. Ways to prevent fungal degradation include keeping the wood dry. The majority of hydrophobic and wood modification systems have been tested only on freshly treated wood. Little information is available on how various wood-based materials perform after a certain period of weathering. To elucidate this question, 17 wood samples were tested from the following species: oak (Quercus), sweet chestnut (Castanea sativa), European larch (Larix decidua), Scots pine heartwood and sapwood (Pinus sylvestris), Norway spruce (Picea abies), and beech (Fagus sylvatica). Moisture performance of the wood samples was improved with thermal modification, wax, oil, and biocide treatment. Specimens were exposed to various degradation-aging factors (blue stain fungi, decay fungi, artificial weathering, and natural weathering). Various moisture performance tests were applied before and after aging: short-term water uptake (tensiometer), long-term water uptake, water vapor tests, drying tests, etc. The water exclusion efficacy of wood was decreased after aging. Aging factors were found to act synergistically and to have a more prominent influence on less durable wood compared to durable or preservative-treated wood. Wax-treated wood performed best, regardless of which moisture performance test was applied.

Bark beetle-induced tree mortality alters stand energy budgets due to water budget changes

Insect outbreaks are major disturbances that affect a land area similar to that of forest fires across North America. The recent mountain pine bark beetle (Dendroctonus ponderosae) outbreak and its associated blue stain fungi (Grosmannia clavigera) are impacting water partitioning processes of forests in the Rocky Mountain region as the spatially heterogeneous disturbance spreads across the landscape. Water cycling may dramatically change due to increasing spatial heterogeneity from uneven mortality. Water and energy storage within trees and soils may also decrease, due to hydraulic failure and mortality caused by blue stain fungi followed by shifts in the water budget. This forest disturbance was unique in comparison to fire or timber harvesting because water fluxes were altered before significant structural change occurred to the canopy. We investigated the impacts of bark beetles on lodgepole pine (Pinus contorta) stand and ecosystem level hydrologic processes and the resulting vertical and horizontal spatial variability in energy storage. Bark beetle-impacted stands had on average 57 % higher soil moisture, 1.5 °C higher soil temperature, and 0.8 °C higher tree bole temperature over four growing seasons compared to unimpacted stands. Seasonal latent heat flux was highly correlated with soil moisture. Thus, high mortality levels led to an increase in ecosystem level Bowen ratio as sensible heat fluxes increased yearly and latent heat fluxes varied with soil moisture levels. Decline in canopy biomass (leaf, stem, and branch) was not seen, but ground-to-atmosphere longwave radiation flux increased, as the ground surface was a larger component of the longwave radiation. Variability in soil, latent, and sensible heat flux and radiation measurements increased during the disturbance. Accounting for stand level variability in water and energy fluxes will provide a method to quantify potential drivers of ecosystem processes and services as well as lead to greater confidence in measurements for all dynamic disturbances.

The diversity of mtDNA rns introns among strains of Ophiostoma piliferum, Ophiostoma pluriannulatum and related species.

BackgroundBased on previous studies, it was suspected that the mitochondrial rns gene within the Ophiostomatales is rich in introns. This study focused on a collection of strains representing Ophiostoma piliferum, Ophiostoma pluriannulatum and related species that cause blue-stain; these fungi colonize the sapwood of trees and impart a dark stain. This reduces the value of the lumber. The goal was to examine the mtDNA rns intron landscape for these important blue stain fungi in order to facilitate future annotation of mitochondrial genomes (mtDNA) and to potentially identify mtDNA introns that can encode homing endonucleases which may have applications in biotechnology.ResultsComparative sequence analysis identified five intron insertion sites among the ophiostomatoid fungi examined. Positions mS379 and mS952 harbor group II introns, the mS379 intron encodes a reverse transcriptase, and the mS952 intron encodes a potential homing endonuclease. Positions mS569, mS1224, and mS1247 have group I introns inserted and these encode intact or eroded homing endonuclease open reading frames (ORF). Phylogenetic analysis of the intron ORFs showed that they can be found in the same insertion site in closely and distantly related species.ConclusionsBased on the molecular markers examined (rDNA internal transcribed spacers and rns introns), strains representing O. pilifera, O. pluriannulatum and Ophiostoma novae-zelandiae could not be resolved. Phylogenetic studies suggest that introns are gained and lost and that horizontal transfer could explain the presence of related intron in distantly related fungi. With regard to the mS379 group II intron, this study shows that mitochondrial group II introns and their reverse transcriptases may also follow the life cycle previously proposed for group I introns and their homing endonucleases. This consists of intron invasion, decay of intron ORF, loss of intron, and possible reinvasion.Electronic supplementary materialThe online version of this article (doi:10.1186/s40064-016-3076-6) contains supplementary material, which is available to authorized users.

Beneath the bark: associations among Sirex noctilio development, bluestain fungi, and pine host species in North America

1. Invasive species with global distributions encounter unique environmental and biotic variables that can greatly affect the magnitude of their impact. The European woodwasp, Sirex noctilio Fabricius, is a prime example that has invaded climatically and ecologically distinct ecosystems across the Southern Hemisphere and, more recently, North America.2. Northeastern North America presents a unique set of conditions, including pine host species, native parasitoids, a diverse assemblage of native co‐colonising insects, and fungal associates of these co‐colonisers. In North America, S. noctilio attacks both a naturalised ancestral host (Pinus sylvestris L.) from Europe and a naïve native host (P. resinosa). A large assemblage of insects and their associated bluestaining ophiostomatoid fungi colonise these pines. Competition between S. noctilio and this group is a hypothesised mechanism of biotic resistance in the invaded region of North America, possibly via superior resource capture abilities or alteration of host tissue by bluestain fungi.3. Investigating these ecological interactions is challenging because they manifest deep in the xylem tissue. To overcome this, 30 experimentally stressed trees were systematically dissected with an electric log splitter to investigate the effects of bluestain fungi and tree factors on S. noctilio development and parasitism by native hymenopterans.4. Body size and colonisation density were affected by pine species, with S. noctilio being 25% larger and densities three‐fold greater in P. sylvestris than P. resinosa. Survivorship was slightly negatively correlated with the proportional volume of bluestain infection. Interestingly, rhyssine (Rhyssa and Megarhyssa spp.) parasitism responded positively to greater S. noctilio density, but there was no density relationship with Ibalia leucospoides ensiger parasitism. Pine host species appears to play a strong role in S. noctilio development, which is important considering uninvaded regions of North America have a diversity of pine species that likely vary in their susceptibility to this woodborer.

The Ophiostoma clavatum species complex: a newly defined group in the Ophiostomatales including three novel taxa.

Two species of blue-stain fungi with similar morphologies, Ophiostoma brunneo-ciliatum and Ophiostomaclavatum, are associates of bark beetles infesting Pinus spp. in Europe. This has raised questions whether they represent distinct taxa. Absence of herbarium specimens and contaminated or mistakenly identified cultures of O.brunneo-ciliatum and O.clavatum have accentuated the uncertainty regarding their correct identification. The aim of this study was to reconsider the identity of European isolates reported as O.brunneo-ciliatum and O.clavatum by applying DNA-based identification methods, and to provide appropriate type specimens for them. Phylogenetic analyses of the ITS, βT, TEF-1α and CAL gene sequences revealed that the investigated isolates represent a complex of seven cryptic species. The study confirmed that ITS data is insufficient to delineate species in some Ophiostoma species clusters. Lectotypes and epitypes were designated for O.clavatum and O.brunneo-ciliatum, and three new species, Ophiostomabrunneolum, Ophiostomamacroclavatum and Ophiostomapseudocatenulatum, are described in the newly defined O.clavatum-complex. The other two species included in the complex are Ophiostoma ainoae and Ophiostoma tapionis. The results suggest co-evolution of these fungi in association with specific bark beetles. The results also confirm the identity of the fungus associated with the pine bark beetle Ips acuminatus as O.clavatum, while O.brunneo-ciliatum appears to be mainly associated with another pine bark beetle, Ips sexdentatus.

Effects of Grosmannia clavigera and Leptographium longiclavatum on Western White Pine Seedlings and the Fungicidal Activity of Alamo®, Arbotect®, and TREE-äge®

Bark beetles carry a number of associated organisms that are transferred to the host tree upon attack that are thought to play a role in tree decline. To assess the pathogenicity to western white pine (WWP; Pinus monticola) of fungi carried by the mountain pine beetle (MPB; Dendroctonus ponderosae), and to evaluate the potential for systemic prophylactic treatments for reducing fungal impacts, experiments were conducted with WWP seedlings to meet three objectives: 1) evaluate pathogenicity of two MPB-associated blue-stain fungi; 2) evaluate phytotoxicity of tree injection products; 3) evaluate the anti-fungal activity of tree injection products, in vitro and in vivo, toward the associated blue-staining fungi. To evaluate pathogenicity, seedlings were inoculated with Grosmannia clavigera or Leptographium longiclavatum, common fungal associates of MPB. Seedling mortality at four months after inoculation was 50% with L. longiclavatum and 90% with G. clavigera, both significantly higher than controls and thereby demonstrating pathogenicity. Phytotoxic effects of TREE-äge®, Alamo®, and Arbotect® were evaluated by stem injection; no phytotoxic effects were observed. Anti-fungal properties of the same three products were evaluated in vitro against G. clavigera, where Alamo was most active. Co-inoculation of G. clavigera and L. longiclavatum into seedlings after a stem injection of Alamo showed significantly less mortality and lesion formation than either species alone. Results support the hypothesis that MPB blue-stain associates, particularly G. clavigera, promote death of WWP when attacked by MPB. These findings suggest that the administration of a fungicide with insecticide for tree protection against bark beetles may be advantageous.

Thermo-hydro treated (THT) birch veneers for producing plywood with improved properties

Abstract The effect of thermo-hydro treatment (THT) on the properties of birch (Betula spp.) wood veneers has been studied. THT was carried out in a multi-functional pilot scale wood modification device of wood treatment technology (WTT, Latvia) under elevated water vapor pressure conditions at four combinations of temperature and treatment time (°C/min): 150/10; 150/50; 160/10 and 160/50. After THT, the following veneer properties were examined: mass loss (ML), chemical composition, bending strength (BS), tensile strength (TS), equilibrium moisture content (EMC), resistance to decay by mould and blue stain fungi, and surface contact angle (CA). The chemical components were changed by THT. Increased THT temperature and time resulted in hydrophobization of veneers as indicated by decreasing EMC and increasing CA data. All THT were effective against wood discoloring fungi, although insufficient decay resistance was observed. The mechanical strength properties of THT veneers were also deteriorated.

Antioxidant defences of Norway spruce bark against bark beetles and its associated blue-stain fungus

Abstract Bark beetles and their fungal associates are integral parts of forest ecosystems, the European spruce bark beetle (Ips typographus Linnaeus, 1758) and the associated pathogenic blue stain fungus Ceratocystis polonica (SIEM.) C. MOREAU, are the most devastating pests regarding Norway spruce [Picea abies (L.) H. KARST.]. Bark beetles commonly inhabit weakened and felled trees as well as vital trees. They cause physiological disorders in trees by destroying a phloem and cambium or interrupt the transpiration -ow in the xylem. Conifers have a wide range of effective defence mechanisms that are based on the inner bark anatomy and physiological state of the tree. The basic function of bark defences is to protect the nutrient-and energy-rich phloem, the vital meristematic region of the vascular cambium, and the transpiration -ow in the sapwood. The main area of defence mechanisms is secondary phloem, which is physically and chemically protected by polyphenolic parenchyma (PP) cells, sclerenchyma, calcium oxalate crystals and resin ducts. Conifer trunk pest resistance includes constitutive, inducible defences and acquired resistance. Both constitutive and inducible defences may deter beetle invasion, impede fungal growth and close entrance wounds. During a successful attack, systemic acquired resistance (SAR) becomes effective and represents a third defence strategy. It gradually develops throughout the plant and provides a systemic change within the whole tree’s metabolism, which is maintained over a longer period of time. The broad range of defence mechanisms that contribute to the activation and utilisation of SAR, includes antioxidants and antioxidant enzymes, which are generally linked to the actions of reactive oxygen species (ROS). The presented review discusses the current knowledge on the antioxidant defence strategies of spruce inner bark against the bark beetle (Ips typographus) and associated blue stain fungus (Ceratocystis polonica).

Sirex woodwasp range expansion in Australia: performance and parasitism on two commercial pine species

Sirex woodwasp was detected in Queensland in 2009 and rapidly established in softwood plantations (Pinus radiata and P. taeda) in southern border regions. Biocontrol inoculations of Deladenus siricidicola began soon after, and adults were monitored to assess the success of the programme. Wasp size, sex ratios, emergence phenology and nematode parasitism rates were recorded, along with the assessment of wild-caught females. Patterns varied within and among seasons, but overall, P. taeda appeared to be a less suitable host than P. radiata, producing smaller adults, lower fat body content and fewer females. Sirex emerging from P. taeda also showed lower levels of nematode parasitism, possibly due to interactions with the more abundant blue-stain fungus in this host. Sirex adults generally emerged between November and March, with distinct peaks in January and March, separated by a marked drop in emergence in early February. Temperature provided the best correlate of seasonal emergence, with fortnights with higher mean minimum temperatures having higher numbers of Sirex emerging. This has implications for the anticipated northward spread of Sirex into sub-tropical coastal plantation regions. Following four seasons of inundative release of nematodes in Queensland, parasitism rates remain low and have resulted in only partial sterilization of infected females.

Commensal relation between Bursaphelenchus xylophilus (Nematoda: Aphelenchoididae) and Monochamus alternatus (Coleoptera: Cerambycidae) within pine trees

Bursaphelenchus xylophilus (Steiner et Buhrer) Nickle causes pine wilt disease and is transmitted by Monochamus alternatus Hope adults in Japan. To determine the effects of the beetle larvae on the nematode population and the effects of the nematode population on beetle larval growth, we inoculated fresh pine bolts with various combinations of B. xylophilus, M. alternatus, and the blue-stain fungus Ophiostoma minus (Hedgc.) Syd. & P. Syd., the food of the nematodes. We also compared the content of ergosterol among the phloem, xylem, and larval frass. The nematode density was 22 or 25 times higher in frass than in phloem and the lowest in xylem, indicating positive effects of beetle larvae on the nematode population growth. Frass had twice higher ergosterol content than the phloem, indicating the fungal mycelial content was greatest in the frass. The difference in the content of fungal mycelia could explain in part the difference in B. xylophilus density between the frass and phloem. By contrast, B. xylophilus did not affect the growth and developmental rate of M. alternatus. This study showed that the relation between the beetle and nematode populations changes from mutualism to commensalism corresponding to the dispersal to reproduction stages of the nematode population.

The occurrence and pathogenicity of Geosmithia spp. and common blue-stain fungi associated with pine bark beetles in planted forests in Israel

Fungi associated with the bark beetles Orthotomicus erosus, Tomicus destruens and Pityogenes calcaratus were sampled in various pine forests throughout Israel. Three ophiostomatoid fungi, Ophiostoma ips, Graphilbum rectangulosporium and Leptographium wingfieldii, and a fourth non-ophiostomatoid fungus, Geosmithia sp. 24, were identified by using morphological characteristics and molecular genetic analyses. O. ips, the most common fungus, was mainly isolated from O. erosus. The least common fungus, G. rectangulosporium, was frequently isolated from all three studied scolytids, while L. wingfieldii was almost exclusively associated with T. destruens. The fourth fungus, Geosmithia sp. 24, was isolated from both O. erosus and P. calcaratus. This is the first time that an association between O. erosus and a Geosmithia sp. has been reported. Our findings also suggest that Geosmithia sp. 24 can be separated into two distinct sub-groups by molecular analyses. Pathogenicity was demonstrated only for L. wingfieldii, both on Aleppo and brutia pine, exclusively under controlled conditions (25 ± 5 °C) but not at elevated temperatures.

Ophiostomatoid fungi associated with declined Pinus pinaster stands in Spain

Aim of study: We studied the presence of fungi and distribution patterns in relation to the health status of declining Pinus pinaster trees.Area of study: Trees in two declining stands in Central Spain were allotted to three declining classes...Material and Methods: Trees in two declining stands in Central Spain were allotted to three declining classes (healthy, declining and recently dead) and 3 trees of each class were felled in each stand. Wood slides (phloem and xylem) were taken at six positions along the trees and samples collected from fungal identification.Main results: A total of 21 fungal taxa were isolated and identified; eleven of these species belonged to the Ophiostomatoid group. Ophiostoma minus was the most frequently isolated fungus and was identified in 22% of the samples, mainly associated to dead and diseased trees.Research highlights: Together these results suggest a putative association of O. minor with the decline in this area, and thus we suggest paying more attention to this fungus as a potential agent of decline in P. pinaster stands.Key words: Ophiostomatoid fungi; forest pathology; bluestain fungi; multivariate analyses.Abbreviations: UTM: Universal Transverse Mercator coordinate system; MEA: Malt Extract Agar; DNA: Deoxyribonucleid acid; ITS: Internal Transcribed Spacer; BLAST: Basic Local Alignment Search Tool; CCA: Canonical Correspondence Analyses; PWN: Pine Wood Nematode.