A standard soil block test was carried out to establish the biocidal efficacy of seven AACs and six copper-Ethoduomeen or Propoduomeen complexes against three wood destroying fungi (Gloeophyllum trabeum, Postia placenta and Trametes versicolor). The QAC derivatives (BCAD-amine oxide, Coco-amine oxide, Coco-amine, Ethoxyl-amine and Coco-CIP) required relatively high concentrations to control decay (toxic threshold: 3.5-10 kg/m(3)). Ethoduomeen C/13 and Coco-amide were unable to control the three wood destroying fungi over the retention range studied. All six copper-amine formulations prevented decay by the three fungi. F-II (copper-Ethoduomeen C / 13, 1 : 1 w / w) and F-V (copper-Ethoduomeen C / 13, 2 : 1 w / w) proved to be the most effective (< 1.35 kg/m(-3) toxic threshold for all three fungi).
Seventeen fungi isolated from hardwood stakes at field sites used by the Forest Research Institute Malaysia (Trichoderma, Chaetomium, Curvularia, Ceriporia, Arthrographis and Paecilomyces species) were screened for their antagonism against two white rot fungi frequently isolated from tropical timber. Pyenoporus sanguineus and Schizophyllum commune. A range of in vitro methods were performed using nutritionally rich malt extract and low nutrient minimal media. A dual plate method showed that antagonism of hardwood decay fungi varied with isolate and the medium used; Trichoderma species exhibited the greatest antagonism on malt extract agar. Culture filtrates of most isolates inhibited growth of both decay fungi, but inhibition varied with isolate and media. Inhibitory volatile metabolites and siderophores were produced by some isolates on both minimal and malt extract media. Production of laminarinase and chitinase was dependent on the medium type used, The specific activity of both enzymes was proportionally higher in the low nutrient medium. Trichoderma isolates were, antagonistic to hardwood decay fungi based on in vitro testing, although the variation in mechanisms between species and strains is diverse. Some isolates exhibit antagonism in a low nutrient medium and these may prove to be more successful as biological control agents in situ. Further studies are being undertaken using wood as the test medium.
A complex nonlinear-modelling-based electrical impedance spectroscopy (EIS) for the analysis of decay (soft rot and bacteria) in wood was introduced. Small wood specimens (5 x 10 x 100 mm) including three degrees of decay (control and two decay conditions) were measured by impedance spectroscopy at frequencies between 80 Hz and 1 MHz. The effect of decay on impedance was studied by EIS-modelling and constant frequency parameter analysis at two different moisture content levels below fibre saturation point. Two ZC-circuits in series were used in modelling. The distribution parameter v(1) of the double ZC-model decreased with increasing decay, the reduced values of the distribution parameter were affected by the increased variability in the wood cell structure. The effect of decay on constant frequency parameters was neglible compared to the moisture content effect. Thus, it was possible to estimate both decay condition and moisture content level of each specimen by combined method of EIS-modelling and constant frequency parameter analysis.
The termiticidal efficacy of disodium. octaborate tetrahydrate (DOT) was evaluated after it was impregnated into seasoned Pinus radiata D. Don, Acacia melanoxylon R. Br. and Eucalyptus obliqua L'Herit. flooring (air-dried, seasoned and green timber), and exposed to field-collected Coptotermes acinaciformis (Froggatt) in the Accelerated Field Simulator (AFS). The AFS test was designed to simulate a building with a suspended timber floor. The nominal retentions of treated framing were 0, 0.5, 1.0 and 1.2% BAE. Termite feeding, foraging activity and any subsequent mortality over the range of borate-treated timbers were examined. The results after 32 weeks of the completed test indicated that borate may be useful both as a slow-acting toxicant to reduce termite infestations from building structures to less than half of the original population and as an anti-feedant insecticide at higher retentions to prevent the attack by termites to structural timber. The results show that the presence of higher retention treated timber provides no protection to adjacent untreated timber even if that timber is in close proximity to timber that is treated with even a good diffusing chemical such as borate. The economic lethal threshold (ELT) of the borate compounds when used as wood preservatives in H2 hazard levels was over 1 % m/m BAE.
A laboratory leaching trial combining a static and a flowing seawater system was carried out to determine the rates of release of copper, chromium and arsenic from the surface of Scots pine panels vacuum-pressure treated to target retentions of 3, 6, 12, 24 and 48 kgm(-3) CCA. Untreated and treated panels were exposed in flowing seawater for up to 8 weeks followed by 2 weeks submersion in static seawater which was taken for analysis. The study revealed a leaching hierarchy of Cu > Cr > As which supports the findings of other investigators. Over the 10 week leaching trial there was a time-related decrease in the rate of copper and chromium loss. Over the first week of leaching in flowing seawater. the rates of loss of copper and chromium decreased to between one half and one seventh followed by lower rates of leaching over the remaining eight weeks of the investigation. The rate of loss of arsenic from the wood was negligible over the same period. The data are compared with minimal leaching rates of toxins from the surface of anti-fouling paints, and are discussed in terms of the fouling communities which are established on Scots pine panels treated to similar target retentions following exposure in estuarine and coastal locations.
Chlorothalonil in oil was compared as a wood preservative with copper-chromium-arsenic salt (CCA) in Pinus radiata D. Don and Eucalyptus regnans F Muell. sapwood. Treated stakes were placed in soil in an accelerated field simulator (AFS) where the main hazard was determined to be soft rot. Water and toluene treated control stakes were heavily decayed after 1-3 years, while oil treated controls were still serviceable after 5-5.5 years. Chlorothalonil was significantly more effective than CCA at protecting timber. In P. radiata, a minimum chlorothalonil retention of 0.8 kg/m(3) was required to protect stakes for eight years in the AFS, compared to 6.9 kg/m(3) for CCA. All CCA retentions up to and including 21.8 kg/m(3) had failed in E. regnans within eight years, whereas a minimum retention of 10.6 kg/m(3) chlorothalonil ensured serviceability.
To investigate whether or how the occurrence of stain varies depending on season, a seasonal survey of staining fungi was conducted in a sawmill in Princeton in British Columbia province in 1998, using fresh lodgepole pine logs and lumber. Fungal samplings were carried out in three different seasons including the spring, summer, and autumn of that year. The 510 isolates obtained were distributed in five different genera representing at last 10 different species. Around 30 isolates remain to be identified. Species belonging to Ophiostoma, Ceratocystis and Leptographium genera contributed to 95.5% of all the isolates, while Aureobasidium/Hormonema constituted the remaining 4.5%. Leptographium spp., O. floccosum and O. piceae were found throughout the tested seasons while Ophiostoma sp. E was only present in May and October. O, piliferum and O. minus were not found in May. Leptographium spp. were more frequently found in August. Even if the occurrence of fungal species varied depending on season, stain on lumber was produced in all the tested seasons. However, stain in logs varied and to an extent depended on seasons. Overall, our results showed that the major bluestain species (Leptographium spp., O. floccosum, and O. piceae) occur throughout different seasons. Freshness of wood is considered being attributed to the variance in their occurrence ensuing deviation in stain in different seasons.
Sentry((R)) is a newly developed antisapstain treatment containing methylene bisthiocyanate (MBT) as one of the active ingredients. In recent laboratory and field trials. Sentry((R)) gave better protection of unseasoned radiata pine against wood deteriorating organisms compared with other benchmark products. This was attributed to the ability of MBT to diffuse into green wood arresting fungal pre-infection. However, MBT vapour may also play a role in controlling fungal pre-infections but this has not been previously investigated. In the current study, mycelial growth and spore germination of key wood inhabiting fungi, Leptographium procerum, Ophiostoma piliferum, Sphaeropsis sapinea, Phlebiopsis gigantea and Trichoderma viride, were quantified after exposure to vapour from filter paper treated with solutions containing 0.125%, 0.25% and 0.5% w/w of MBT (product), and compared with a solvent blank (0.5% w/w of the same product without MBT) and distilled water (control). Except for the mycelium of T viride, a clear dose response relationship was observed for fungi as there was a decrease in mycelial growth with increasing MBT vapour concentration. At 0.5% w/w of product, growth of L. procerum, O. piliferum and P. gigantea was completely arrested while S. sapinea experienced 90% reduction in growth. Normal hyphal growth resumed after treated cultures of L. procerum, O. piliferum and P. gigantea were transferred onto fresh malt agar media suggesting a fungistatic mode of action of MBT vapour. However. a sporotoxic effect was observed after exposure of spores to MBT vapour, irrespective of the treatment concentration used. except for T viride where spore germination was only inhibited at 0.5% w/w of product.
The objective of the current study was to determine if a relationship exists between the decay capacity of different strains of Phlebiopsis gigantea and the production of extracellular hydrolytic enzyme secretion. A soil block method was used to determine mass weight loss of Pinus radiata and Fagus sylvatica following 10 weeks incubation with different strains of P. gigantea. Mass weight losses ranged from 0.3% to 26.5% on P radiata and 0.1% to 52.2% on F sylvatica. Gloeophyllum trabeum included for comparison, caused the highest mass weight loss (70%) of all fungi tested, irrespective of wood species used. Extracellular enzyme activity varied greatly between fungal species and strains and specific enzyme examined. There was no apparent relationship between decay capacity and enzyme activity for any of the fungi used.
Trichoderma species previously isolated from fumigated Douglas-fir stumps were tested for the ability to control wood-staining fungi. Ponderosa pine wafers were inoculated first with spore suspensions of one of 146 Trichoderma isolates, then with a mixture of two wood-staining fungi (Ohpiostoma piceae and Alternaria alternata). After 4 weeks the wafers were visually rated for discoloration caused by the biocontrol isolate or the stain fungi. Many of the potential biocontrol isolates reduced or eliminated discoloration caused by the stain fungi, but some of these same isolates also discolored the wood. More than one-third of the biocontrol isolates reduced total discoloration to below 15% of the wood surface. Most of these effective isolates were T. viride or T. virens. Further screening of effective biocontrol isolates that cause the least discoloration is recommended, as is the use of these isolates in combination.
This paper presents an assessment of the effectiveness of three straight chain alkyl anhydrides as chemical modifiers in improving the resistance of susceptible softwood to attack by wood-destroying insect larvae of the house longhorn beetle (Hylotrupes bajulus). The data from standard European tests indicates that the overall resistance to insect attack is enhanced through chemical modification. In addition the data demonstrate that acetic, propionic and butyric anhydrides all performed well in these insect tests; acetic anhydride conferring the greatest degree of bioresistance with weight percent gain (WPG).
Delignification of tracheids within Norway spruce wood by Stereum sanguino-lentum was associated with the presence of radial and concentric clefts containing minute cell wall entities in the secondary wall (S-2). Light and transmission electron microscopy (TEM) revealed that hyphae growing on the inner secondary wall (S-3) within the lumen of tracheids induced selective delignification and the formation of radial and concentric clefts in the adjoining secondary cell wall (S-2). Enzymatic action and the resulting shrinkage stresses may cause the wall to separate along inherent radial and concentric planes of weakness. The present study supports former observations of a radial and concentric arrangement of cell wall constituents within the secondary wall (S-2).
The effect of 7 anti-sapstain chemicals and their mixtures incorporated into a medium on spore germination of Graphium sp. was microscopically examined. The chemicals were also tested for their SH-inhibitory effect using a glutathione-containing medium. Spore germination of Graphium sp. tvas completely prohibited by 5 chemicals: IPBC, DCOI, MBT, chlorothalonil and TMSP. Non-SH inhibitors, carbendazim and TCP allowed some spore germination, producing deformed fungal growth. The latter two chemicals, therefore, seemed different in effect on spore germination from others. Chemical mixtures containing IPBC and/or carbendazim produced a good inhibitory effect on spore germination.
Eucalyptus pilularis Sm., Corymbia maculata (Hook.) K. D. Hill & L. A. S. Johnson syn. E. maculata Hook., and Pinus radiata D. Don rounds were treated with either low temperature creosote (K55), high temperature creosote (HTC)I arsenical creosote, Tanalith C, Tanalith C followed by HTC, or Tanalith C followed by arsenical creosote. Specimens were 80-125 mm diameter and 540 mm long. A maximum of four replicates of each timber/treatment combination was exposed in the sea for 20.7 Sears at Sydney and 19.7 years at Port Stephens. Results suggest that K55 is not as effective as HTC in E. pilularis and C. maculata; there is little difference between the performance in timber of HTC anti arsenical creosote; Tanalith C treated P. radiata can be rendered unserviceable by Sphaeroma within six years; Tanalith C treated E. pilularis and C. maculata can fail to teredinids within 16-20 years in NSW; double treatment of Tanalith C followed by either HTC or arsenical creosote ensures that timber specimens will remain serviceable for at least 20 years; and double treatment of Tanalith C + HTC provides better protection than a single treatment of HTC in both P. radiata and C. maculata.
This paper presents the results of a monitoring programme of Sitka spruce timber stored in a sawmill yard in Scotland. Batten surface moisture content, relative humidity and temperature in packs of timber and fungal spoilage were measured using kiln dried and partially air dried timber stacked in several pack types over 3 month periods throughout 1 year. The moisture content and degree of spoilage by stain fungi of each row of each pack type was determined at 6 and 12 weeks after pack construction at 4 times in a year. Inter-relationships are explored between timber surface moisture content, relative humidity within packs, fungal development, location of timber within the packs, pack type and protection from air circulation and precipitation wetting. Greater spoilage by stain fungi developed on partially air dried timber than kiln dried timber. Stain development was largely controlled by water availability. Relative humidity was more important than timber surface moisture content.
Summary The mechanism of wood degradation by white-rot fungi is not understood in detail other than it is involving phenol oxidases (which are lignin-degrading enzymes) and cellulases. The possible role of hydroxyl radicals in degradation by the white-rot fungus Phanerochaete chrysosporium was studied. The production of a low-molecular-weight substance that is secreted was measured periodically. The substance catalyzes a redox reaction between O2 and an electron donor producing hydroxyl radicals in the culture fluid of this fungus with glucose or wood as the carbon source. We examined the possible role(s) of one-electron oxidation activity by phenol oxidases and hydroxyl radicals in wood degradation by this fungus. Assays of phenol oxidase activity showed that P. chrysosporium produced much manganese peroxidase in wood culture, and that the activity peaked early in incubation. The generation of hydroxyl radicals in the redox reaction was related to the rate of wood degradation, but the activity of phenol oxidases was not related. Therefore, hydroxyl radicals are important in wood degradation by this fungus.
Twelve tropical freshwater fungi, isolated from submerged wood, were selected to detect their wood-degrading capabilities and the influence of interactions on the rate of wood decomposition. Wood decay abilities were evaluated by measuring the percentage weight loss of wood blocks. Wood blocks incubated in liquid medium or on agar medium, were covered with mycelium, softened and had weight losses above 5% after 9 and 12 months. This indicates that the fungi tested were able to degrade lignocellulose. Initially, in liquid cultures, greater weight losses were recorded in all wood blocks inoculated with a single inoculum, than those inoculated with the same isolate at opposite ends of the wood blocks. However, this greater weight loss persisted for only certain periods depending on the isolates. Wood blocks with three fungi showed greater weight losses than wood blocks with the equivalent paired fungi. For example, Ophioceras dolichostomum and Ophioceras dolichostomum and Nais aquatica or Ophioceras dolichostomum and Nais aquatica and Nais aquatica caused greater weight losses than Ophioceras dolichostomum and Nais aquatica inoculated separately. The greatest weight losses were recorded in the case of three fungi, Ophioceras dolichostomum, Verticillium sp. and Nais aquatica inoculated simultaneously on triangular wood blocks. Fungi may act synergistically in order to degrade wood cells.
Susceptibility of common sapstaining fungi to antisapstain products was examined using a rapid antisapstain laboratory disc trial. The ability of fungal isolates to colonise radiata pine branchwood discs treated with various commercial antisapstain formulations was used as an indicator of fungicidal susceptibility or tolerance. The results of this investigation showed that under laboratory conditions, susceptibility to antisapstain formulations varied greatly, both between species, and between isolates of the same species. None of the formulations gave consistent control of all the isolates when tested at commercial usage rates. The significance of these results is discussed in terms of design of laboratory antisapstain trials and its potential relevance in the field.
In order to identify organic chemicals possessing wood protecting potential, an evaluation was carried out of a range of commercially available 'quats', using a modified soil block test. Softwood and hardwood sapwood blocks, treated with one of twenty one quats, were exposed to G. trabeum, P. placenta and T. versicolor. Four of the quats (benzyl-coco quat, di-coco quat, ethoxyl(2) quat and hydroxy quat) possess excellent biological efficacy in preventing fungal growth, with the toxic thresholds under 2 kg/m(3). Fifteen other quats showed moderate toxicity against the test fungi, with toxic thresholds centered around 6 to 8 kg/m(3). The variation in the anion of trimethylcocoammonium quats did not influence the efficacy.
