Protecting wood from mould,decay, and termites with multi-component biocide systems

Biocides must be developed for controlling mould establishment on cellulose-based building materials. Accordingly, biocides intended for indoor applications must be non-toxic, non-volatile, odourless, hypoallergenic, and able to provide long-term protection under conditions of high humidity. Multi-component biocide systems were tested in American Wood-Preservers’ Association soil block tests for inhibition of brown-rot and white-rot decay fungi and American Society for Testing and Materials standard tests for inhibition of mould fungi and termites. Multi-component systems combining a borate base supplemented with either 0.1% azole or 0.5% thujaplicin, performed well against the two brown-rot fungi Postia placenta and Gloeophyllum trabeum; the white-rot fungus Coriolus versicolor; the three mould fungi Aspergillus niger, Penicillium chrysogenum, and Trichoderma viride; and the subterranean termite Reticulitermes flavipes (Kollar). It was concluded that for interior applications borate-based multi-component biocide systems can protect wood from decay fungi, mould fungi, and termites, and that a system containing thiabendazole provided protection at a lower retention than the other biocides in this study. Synergy was observed between the borate base and voriconazole in inhibition of mould.     

Evaluation of mold,decay and termite resistance of pine wood treated with zinc- and copper-based nanocompounds

In this work, the resistance of black pine wood (Pinus nigra L.) vacuum-treated with zinc oxide, zinc borate and copper oxide nanoparticles against mold and decay fungi and the subterranean termites was evaluated. Some of the nanocompounds tested were forced with acrylic emulsions to avoid leaching. Results showed that mold fungi were slightly inhibited by nanozinc borate, while the other nanometal preparations did not inhibit mold fungi. Mass loss from fungal attack by Trametes versicolor was significantly inhibited by the zinc-based preparations, while the brown-rot fungus, Tyromyces palustris was not inhibited by the nanometal treatments. Notably, nanozinc borate plus acrylic emulsion imparted very high resistance in pine wood to the white-rot fungus, T. versicolor with a mass loss of 1.8%. Following leaching, all pine specimens treated with nanozinc borate, with or without acrylic emulsion, strongly inhibited termite feeding, i.e. mass losses varying at 5.2–5.4%. In contrast, the copper-based treatments were much less effective against the subterranean termites, Coptotermes formosanus. In general, nanozinc borate possessed favorable properties, that is, inhibition of termite feeding and decay by T. versicolor.     

Micronized Copper Wood Preservatives: Efficacy of Ion,Nano, and Bulk Copper against the Brown Rot Fungus Rhodonia placenta

Recently introduced micronized copper (MC) formulations, consisting of a nanosized fraction of basic copper (Cu) carbonate (CuCO₃·Cu(OH)₂) nanoparticles (NPs), were introduced to the market for wood protection. Cu NPs may presumably be more effective against wood-destroying fungi than bulk or ionic Cu compounds. In particular, Cu- tolerant wood-destroying fungi may not recognize NPs, which may penetrate into fungal cell walls and membranes and exert their impact. The objective of this study was to assess if MC wood preservative formulations have a superior efficacy against Cu-tolerant wood-destroying fungi due to nano effects than conventional Cu biocides. After screening a range of wood-destroying fungi for their resistance to Cu, we investigated fungal growth of the Cu-tolerant fungus Rhodonia placenta in solid and liquid media and on wood treated with MC azole (MCA). In liquid cultures we evaluated the fungal response to ion, nano and bulk Cu distinguishing the ionic and particle effects by means of the Cu²⁺ chelator ammonium tetrathiomolybdate (TTM) and measuring fungal biomass, oxalic acid production and laccase activity of R. placenta. Our results do not support the presence of particular nano effects of MCA against R. placenta that would account for an increased antifungal efficacy, but provide evidence that attribute the main effectiveness of MCA to azoles.     

Discovery of highly potent novel antifungal azoles by structure-based rational design

On the basis of the active site of lanosterol 14α-demethylase from Candida albicans (CACYP51), a series of new azoles were designed and synthesized. All the new azoles show excellent in vitro activity against most of the tested pathogenic fungi, which represent a class of promising leads for the development of novel antifungal agents. The MIC₈₀ value of compounds 8c, 8i and 8n against C. albicans is 0.001 μg/mL, indicating that these compounds are more potent than fluconazole, itraconazole and voriconazole. Flexible molecular docking was used to analyze the structure–activity relationships (SARs) of the compounds. The designed compounds interact with CACYP51 through hydrophobic, van der Waals and hydrogen-bonding interactions.     

Antifungal effect of essential oils on southern yellow pine

Moisture management remains the most critical factor for controlling mold growth on wood and wood products during storage, construction, and while in service. When moisture management practices fail to adequately control moisture, plant extracts demonstrating antifungal properties may provide protection for these applications. The objective of this study was to evaluate the antifungal properties of natural plant extracts, such as essential oils, for use on wood. Seven essential oils were evaluated for their ability to inhibit growth of Aspergillus niger, Trichoderma viride, and Penicillium chrysogenum on southern yellow pine (SYP) stakes that were either dip treated or exposed to vapors of the test oils. Thyme and Egyptian geranium oil inhibited growth of all test fungi for 20 weeks. Likewise, dill weed oil vapors inhibited all test fungi for at least 20 weeks. Comparison of two mold test apparatuses—Petri dish test and tank test chambers—gave similar results for thyme oil. These findings support the application of essential oils for surface treatment or vapor exposure of wood to prevent mold infestation.     

Nematicidal activity of (Z)-ligustilide isolated from Angelica tenuissima Nakai root extract against the pine wood nematode Bursaphelenchus xylophilus

In this study, we investigated the nematicidal activities of the ethanol extracts of 49 medicinal plants against the pine wood nematode, Bursaphelenchus xylophilus, and isolated a main nematicidal constituent, (Z)-ligustilide, from Angelica tenuissima Nakai root extract. Among the 49 plant extracts, only the A. tenuissima root extract showed the strong nematicidal activity against the pine wood nematode, with a 92.3% mortality rate at a concentration of 2 mg/mL. Based on bioassay-guided isolation and gas chromatography-mass spectrometry (GC-MS) analysis, (Z)-ligustilide was identified as the active component of A. tenuissima root extract at 73.6% of the total content ratio. The LC₅₀ value of (Z)-ligustilide against the pine wood nematode was 0.24 mg/mL. Our results indicated that (Z)-ligustilide as well as A. tenuissima root extract can be potential candidates for novel trunk injection agents against the pine wood nematode.     

Selective Degradation of Wood Components by White-Rot Fungi

In order to find naturally occurring white-rot fungi which preferentially degrade lignin. 25 different species of such fungi were cultivated on pine wood blocks and on kraft lignin agar plates with and without cellulose. Due to differences in phenol oxidase reactions on the kraft lignin agar plates, the 25 fungi could be divided into two groups, 1 and 2, which also differed in other properties. The three Group I fungi Sporotrichum pulverulentum, Phanerochaete sp. L1 and Polyporus dichrous produced high levels of endo-l,4-β-glucanase and cellobiose:quinone oxidoreductase in shaking cellulose flasks and a low level of phenol oxidase in standing wood meal flasks, The four fungi Merulius tremellosus, Phlebia radiata, Pycuoporus cinnabarinus and Pleurotus ostreatus from Group 2, on the other hand, produced low levels of endo-1,4-β-glucanase and cellobiose:.quinone oxidoreductase in the cellulose. flasks and a high level of phenol oxidase in the wood meal flasks. Analyses of pine wood blocks degraded by the above-mentioned fungi in the presence of either malt extract, asparagine or NH₄H₂PO₄ revealed that malt extract gave good lignin degradation. In the presence of this nutrient source. P. cinnabarinus, at 3.4% weight loss, even degraded 12.5% lignin without loss of cellulose or mannan. No common degradation pattern was, however, obtained using mall extract, asparagine or NH₄H₂PO₄, It is suggested that while-rot fungi, which preferentially degrade lignin, may be found among Group 2 fungi producing large amounts of phenol oxidases.     

Nutrient mobilization by plasmodium of myxomycete Physarum rigidum in deadwood

To assess the nutrient mobilization ability of myxomycete plasmodia in deadwood, a microcosm experiment was conducted. Alive or dead plasmodia of a common lignicolous myxomycete, Physarum rigidum, were inoculated on field-collected crushed wood powder of white-rot or brown-rot pine wood and incubated for 24 d. The activity of living plasmodia led to increased concentrations of Ca²⁺, K⁺, Mg²⁺, Na⁺, and Cl⁻, but lower PO₄^3– concentrations in the wood powder. For NO₃⁻ concentration, the effect of living plasmodia was negative in white-rotted wood but positive in brown-rotted wood. These results suggest that the plasmodium of P. rigidum has the ability to mobilize nutrients in deadwood.     

Design,synthesis and antifungal activity of amide and imine derivatives containing a kakuol moiety

In continuation of our program to discover new potential antifungal agents, a series of amide and imine derivatives containing a kakuol moiety were synthesized and characterized by the spectroscopic analysis. By using the mycelium growth rate method, the target compounds were evaluated systematically for antifungal activities in vitro against four plant pathogenic fungi, and structure–activity relationships (SAR) were derived. Compounds 7d, 7e, 7h, 7i and 7r showed obvious inhibitory activity against the corresponding tested fungi at 50 μg/mL. Especially, compounds 7e and 7r displayed more potent antifungal activity against B. cinerea than that of thiabendazole (a positive control). Moreover, compound 7e also exhibited good activity against A. alternata with EC₅₀ values of 11.0 µg/mL, and the value was slightly superior to that of thiabendazole (EC₅₀ = 14.9 µg/mL). SAR analysis showed that the ether group was a highly sensitive structural moiety to the activity and the type as well as position of substituents on benzene ring could make some effects on the activity.     

Do the unique properties of nanometals affect leachability or efficacy against fungi and termites?

Nanotechnology has the potential to affect the field of wood preservation through the creation of new and unique metal biocides with improved properties. This study evaluated leachability and efficacy of southern yellow pine wood treated with copper, zinc, or boron nanoparticles against mould fungi, decay fungi, and Eastern subterranean termites. Results showed that nanocopper with and without surfactant, nanozinc, and nanozinc plus silver with surfactant resisted leaching compared with metal oxide controls. Nearly all nanoboron and boric acid was released from the treated wood specimens during leaching. Mould fungi were moderately inhibited by nanozinc oxide with surfactant, but the other nanometal preparations did not significantly inhibit mould fungi. Mass loss from Gloeophyllum trabeum was significantly inhibited by all copper preparations, while Antrodia sp. was not inhibited by nanometal treatments. Nanometals imparted high resistance in southern yellow pine to the white-rot fungus, Trametes versicolor. Unleached specimens treated with nanoboron or nanozinc plus surfactant caused 100% and 31% mortality, respectively. All specimens treated with nanozinc or nanozinc plus silver inhibited termite feeding, but the copper treatments were less effective against termites. Nanozinc possessed the most favorable properties: leach resistance, termite mortality, and inhibition of termite feeding and decay by the white-rot fungus.     

Fungal decay resistance and durability of organosilicon-treated wood

The potential use of organosilicons as protective agents against basidiomycetes attack of wood used in outdoor applications was investigated using Scots pine sapwood and beech specimens. Both mini-blocks and EN 113 specimens were subjected to brown-rot and white-rot fungi. A dose–response could be observed showing that with higher weight percentage gain of the organosilicon, the resistance (i.e., efficacy) against fungi increased. At relatively low weight percentage gains, which are assumed to be economically feasible, Scots pine could be partly protected against decay by Postia placenta and Coniophora puteana and beech could be partly protected against decay by C. puteana and Trametes versicolor. Full protection was achieved by some silicons for Scots pine sapwood against C. puteana and for beech against T. versicolor. The most promising products were a solvent-based mixture of the alkoxysilanes methyltrimethoxysilane (MTM) and octyltriethoxysilane (OTES) and a water-based micro-emulsion of polydimethylsiloxane (PDMS) and triethoxysilane (TES) when applied above 20 and 30% weight gain for Scots pine and above 30 and 40% weight gain for beech. A water-based mixture of dimethylmethylhydrogen siloxane (DMS) and N-octyltriethoxysilane (n-OTES) was able to protect beech at weight gains above 30%.     

Characterization of main sulfur source of wood-degrading basidiomycetes by S K-edge X-ray absorption near edge spectroscopy (XANES)

The main wood degraders in aerobic terrestrial ecosystems belong to the white- and brown-rot fungi, where their biomass can be created on wood decay only. However, total sulfur (S) concentration in wood is very low and only little is known about the different sulfur compounds in wood today. Sulfur-starved brown-rot fungi Gloeophyllum trabeum and Oligoporus placenta were incubated on sterilized pine wood blocks whereas Lentinus cyathiformis and the white-rot fungi Trametes versicolor were incubated on sterilized beech wood blocks. After 19 weeks of incubation, the S oxidation status was analyzed in wood, in degraded wood, and in biomass of wood-degrading fungi by synchrotron based S K-edge XANES, and total S and sulfate were quantified. Total sulfur and sulfate content in pine wood blocks were approximately 50 and 1 ??g g⁻¹, respectively, while in beech wood approximately 100 and 20 ??g g⁻¹ were found, respectively. Sulfur in beech was dominated by sulfate-esters. In contrast, pine wood also contained larger amounts of reduced S. Three out of four selected fungi caused a reduction of the S oxidation state in wood from oxidized S (sulfate-ester, sulfate) to intermediate S (sulfonate, sulfoxide) or reduced S (thiols, e.g., proteins, peptides, enzyme cofactors). Only O. placenta shifted thiol to sulfonate. Growth experiments of these fungi on selective minimal media showed that in particular cysteine (thiol), sulfonates, and sulfate enhanced total mycelium growth. Consequently, wood-degrading fungi were able to utilize a large variety of different wood S sources for growth but preferentially transformed in vivo sulfate-esters and thiol into biomass structures.     

In vitro activities of voriconazole, fluconazole, itraconazole and amphotericin B against non Candida albicans yeast isolates

Antifungal susceptibility testing was performed on 197 yeast isolates from the BCCM/IHEM biomedical fungi and yeasts collection (Belgian Co-ordinated Collections of Micro-organisms / IPH-Mycology) to study the in vitro activity of voriconazole against fluconazole, itraconazole and amphotericin B. MICs of the four antifungal agents were determined by an adapted NCCLS M27-A microdilution reference method. MIC readings were visually and spectrophotometrically determined. Optical density data were used for calculation of the MIC endpoints. For amphotericin B, the MIC endpoint was defined as the minimal antifungal concentration that exerts 90% inhibition, compared to the control growth. The azoles endpoints were determined at 50% inhibition of growth. The MIC distribution of voriconazole susceptibilities showed that 193 isolates had a MIC < or = 2 microg/ml and 185 a MIC < or = 1 microg/ml. Cross-tabulation of voriconazole, fluconazole, and itraconazole MICs indicated that voriconazole MICs raised with fluconazole and itraconazole MICs. The in vitro data obtained in this study suggest that voriconazole may also be effective treating yeast infection in patients infected with fluconazole or itraconazole resistant isolates.     

Co-occurrence patterns of wood-decaying fungi and ants in dead pines of South Korea

Interaction between fungi and insects such as ants, beetles, wasps and termites inhabiting dead pine trees has significant ecological implication in the forest as they can decompose wood debris and add nutrients to the soil; however, only scarce information is available regarding the interaction between wood-decaying fungi and ants. We investigated wood-decaying fungi co-occurring with ants in dead pine trees of South Korea. A total of 57 pairs of wood-decaying fungi and ants were collected from 11 localities. 30 species of wood-decaying fungi and 14 species of ants were identified based on morphology and molecular analysis. Fungal species belonging to Trichaptum, Xylodon, Hyphodontia, and Ceriporia were dominant and co-occurred with common ant species of Lasius, Camponotus, Pristomyrmex, and Crematogaster across most of the sampling sites. This study provides a new baseline in unravelling the complex interaction between wood-decaying fungi and ants in forest ecosystems.     

Evaluation of Etest Performed in Mueller–Hinton Agar Supplemented with Glucose for Antifungal Susceptibility Testing of Clinical Isolates of Filamentous Fungi

Although reference broth microdilution protocol is currently available for filamentous fungi antifungal susceptibility testing (AFST), simpler alternatives as Etest^® tend to be favoured in clinical routine, making their validation of utmost importance. In this study, Etest^® method using 2 % glucose supplemented Muller–Hinton agar was compared to the Clinical and Laboratory Standards Institute (CLSI) M38-A2 protocol for filamentous fungi AFST. The echinocandins, caspofungin and anidulafungin, the azoles voriconazole and posaconazole, and the polyene amphotericin B were tested against 48 Aspergillus spp., seven Fusarium spp., one Beauveria bassiana and three Paecilomyces lilacinus isolates. The majority of the isolates were susceptible to the antifungals tested, and the overall level of agreement between the CLSI and Etest methods was 71.9 % for one dilution and 99.7 % when using two dilutions. Since interpretative breakpoints for filamentous fungi employing the CLSI or Etest methods are not available yet, the established epidemiological cut-off values for Aspergillus spp. were used to distinguish wild-type isolates from those with acquired resistance mechanisms. Forty-five Aspergillus strains did not evidence resistance mutations.     

Decay and termite resistance of medium density fiberboard (MDF) made from different wood species

Medium density fiberboard (MDF) production worldwide is increasing due to the development of new manufacturing technologies. As a result, MDF products are increasingly utilized in traditional wood applications that require fungal and insect resistance. This study evaluated the ability of white and brown rot fungi and termites to decompose MDF consisting of different wood species by measuring weight loss. Furnish in the boards was prepared from heart and sapwood portions of pine (Pinus nigra Arnold var. pallasiana), beech (Fagus orientalis Lipsky), and European oak (Quercus robur L.) species. Fungal decay resistance tests were performed according to ASTM D 2017-81 standard method using two brown-rot fungi, Gloeophyllum trabeum (Pers. ex Fr.) Murr. (Mad 617), Postia placenta (Fries) M. Larsen et Lombard (Mad 698), and one white-rot fungus, Trametes versicolor (L. ex Ft.) Pilat (Mad 697). MDF and wood specimens were also bioassayed against the eastern subterranean termite, Reticulitermes flavipes (Kollar) in order to determine termite resistance of the specimens. MDF specimens containing oak and mixed furnish demonstrated increased durability against decay fungi. Only pine, oak, and mixed MDF specimens met the 25% or less weight loss limit to be classified resistant according to ASTM D 2017-81 standard method. Overall, MDF specimens made from oak showed better performance than oak solid wood specimens. Accelerated aging according to ASTM D 1037-96a standard method before fungal bioassay decreased fungal resistance of the specimens. In contrast to the fungal bioassay, MDF specimens made from beech and mixed furnish showed decreased weight losses from termite attack after 4 weeks. However, none of the MDF specimens were resistant to termite attack. In severe conditions, the MDFs may require the incorporation of chemical biocides prior to board production for increasing the resistance of MDF to termite attack.     

Fixation,leachability, and decay resistance of wood treated with some commercial extracts and wood preservative salts

Beech (Fagus orientalis) and Scots pine (Pinus sylvestris) wood blocks were treated with some commercial extracts as well as water-based wood preservative salts at various concentrations to increase retention and fixation. The penetration, fixation, and antifungal properties of different treatment solutions were compared with statistical analysis. Retention levels of solutions were generally higher for Scots pine wood than beech wood. The highest retention levels were seen in wood treated with sumac leaf extract and oak valonia extract. Leaching tests indicated that both wood types treated with sumac extracts showed higher retention levels than wood treated with the other fruit and bark extract solutions. Adding 1% water-based wood preservative salts to valonia and sumac leaf extracts increased the retention levels. Concentrations of more than 1% did not contribute to retention either individually or with salt additions. Three percent and higher concentrations of wood-preserving salts accelerated and increased the amount of leaching. The results showed that the extract alone was resistant to leaching. Mycological tests showed that all extractives were significantly effective against wood decay.     

Investigations on natural durability of important European wood species against wood decay fungi. Part 1: Laboratory tests

The durability of heartwood from European larch, Sessile oak and Scots pine was tested in laboratory against wood decay basidiomycetes and soft rot. The durability test was performed according to CEN/TS 15083-1:2005 with Coniophora puteana, Oligoporus (Poria) placenta and Trametes (Coriolus) versicolor. CEN/TS 15083-2:2005 was applied in order to test the timber with a bioactive soil substrate against soil rotting organisms. For Sessile oak, a very high durability against basidiomycetes (DC 1) was found in contrast to a low durability (DC 4) against soft rot fungi. Furthermore the results indicated that the durability of European larch and Scots pine is slightly deteriorated after leaching according to EN 84:1997. Beside this a minor influence of raw density on mass loss was detected for larch.     

Successful Treatment of Invasive Fungal Infection Due to Highly Resistant Aspergillus calidoustus in an Allogeneic Hematopoietic Cell Transplant Recipient

Invasive aspergillosis (IA) is the most common invasive fungal infection following a hematopoietic cell transplant, with emerging cryptic species exhibiting resistance to commonly used antifungals such as azoles. These species have been increasingly found after the introduction of anti-mold prophylaxis. We report a case of a 56-year-old female with primary myelofibrosis whose allogeneic hematopoietic cell transplant was complicated by disseminated fungal infection (skin, lung) due to Aspergillus calidoustus, a cryptic specie. Treatment of Aspergillus species remains challenging as these cryptic species are usually resistant to azoles including voriconazole which is the first line of treatment of IA. Infection was successfully treated with surgical excision and combination antifungal therapy based on in vitro susceptibility and synergy testing. Therapy included isavuconazole, a drug that has been shown to be non-inferior to voriconazole in the treatment of invasive mold infections.