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Preliminary study of the fungicidal and structural variability in copper naphthenates and naphthenic acids
1996 - IRG/WP 96-30114
Copper naphthenates, an oil-borne wood preservative listed by the American Wood-Preservers' Association (AWPA), is manufactured by complexing copper(II) with naphthenic acids. Prior to AWPA listing as a wood preservative, field experiments showed that copper naphthenates generally had good stability and were active against wood-destroying organisms. Recently, however, there have been reports of some copper naphthenate-treated poles rapidly failing. One possible explanation for the varying effectiveness could be that the structure, and resulting biological activity, of the naphthenic acids used to make copper naphthenate may vary. To test this hypothesis several naphthenic acids and copper naphenates were obtained and their fungicidal activity against three wood-destroying fungi measured. In addition, the chemical structure of the naphthenic acids were examined by proton- and carbon- NMR. Different activities were observed, especially against a copper-tolerant fungus. Some apparent correlations were seen between the fungicidal activity and chemical structures for the few samples studied.
T Schultz, D D Nicholas, L L Ingram Jr, T H Fisher

A new concept of oxalic acid biosynthesis in physiology of copper-tolerant brown-rot fungi
2001 - IRG/WP 01-10394
Recently, a wide variety of roles of oxalic acid (oxalate) in wood decay systems have been receiving much attention. Copper tolerance of wood-rotting basidiomycetes has been believed to be due to the detoxification of copper wood preservatives by oxalate produced by these fungi. However, biochemical mechanism of oxalate biosynthesis in relation to physiology of wood-rotting fungi has not been elucidated although two oxalate-forming enzymes, oxaloacetase and glyoxylate dehydrogenase, have been studied in our laboratory. Recently, a new role of glyoxylate cycle in oxalate biosynthesis in wood- rotting fungi has been presented, and the cycle commonly occurred to varying extents among the fungi although they were grown on glucose. Enzymatic analyses showed that isocitrate was cleaved by isocitrate lyase in the glyoxylate cycle rather than oxidized by isocitrate dehydrogenase in tricarboxylic acid (TCA) cycle, and the fungi were found to lack a normal TCA cycle due to the absence of - ketoglutarate dehydrogenase. It is noteworthy that glucose was efficiently converted to oxalate in a theoretical yield of about 80%, accumulating in the culture media of F. palustris. The results further indicate that acetyl-CoA derived from glucose was not completely oxidized to CO2 in TCA cycle but was mainly converted to oxalate with help of the other coupling metabolic cycles, including glyoxylate cycle. Formation of oxalate from several intermediary metabolites using cell-free extracts of F. palustris confirmed that oxalate is also the final product of the metabolic pathway in the in vitro system. Thus, it is proposed as a new concept that most of copper-tolerant brown-rot fungi may acquire the energy by oxidizing glucose to oxalate, i.e. oxalate fermentation expressed in the following equation; Glucose + 5O2 --> 2 Oxalate + 2CO2 + 4H2O.
E Munir, T Hattori, M Shimada

Evaluation of wood treated with copper-based preservatives for Cu loss during exposure to heat and copper-tolerant Bacillus licheniformis
1999 - IRG/WP 99-20155
Copper-based wood preservatives need to be effective against exposure to all types of microorganisms. Wood treated with six copper-based preservatives was exposed to 121°C and 20 psi pressure for 15 minutes under standard autoclave conditions and the copper-tolerant bacterium, Bacillus licheniformis CC01, for 10 d at 28°C and 150 rpm. Sixteen to 37 percent of the copper was released from the wood during autoclaving, with copper citrate demonstrating the highest percent loss. Forty-four to 82 percent of the copper remaining in the samples following autoclaving was removed during exposure to the bacterium in liquid culture; copper naphthenate in oil and ACQ-D had losses of eighty percent or greater of the remaining copper. The bacterium removed as much or more total copper in 4 of 6 gas-sterilized samples (85-94%) than the cumulative effects of steam-sterilization and the bacterium on treated samples. Copper loss from in-service treated wood compromises the efficacy of copper-based wood preservatives.
D M Crawford, C A Clausen

Comparative performance of several ammoniacal copper preservative systems
1997 - IRG/WP 97-30151
The efficacy of several ammoniacal copper-based wood preservative systems was evaluated in this study. The selection of potential co-biocides was based on the results of an agar plate test. Following this, the most promising systems were evaluated in a standard field stake test. Good correlation was found between the agar plate and field stake test results. Of the preservative systems tested, copper/tribromophenol, copper/naphthenic acid, copper/DDAC, and copper/propiconizole were found to be superior against copper tolerant fungi in comparison to the other systems tested after three years of field ground-contact exposure. The performance of copper/benzoic acid was mediocre. Copper/citric acid was ineffective against copper-tolerant fungi, with its performance being no better than copper alone.
D D Nicholas, T Schultz

Efficacy of copper:propiconazole and copper:citrate systems in ground contact exposure at a site with copper tolerant fungi
2003 - IRG/WP 03-30305
Southern yellow pine (SYP) sapwood field stakes were treated with copper alone (ammoniacal copper carbonate, ACC) at four levels, or three levels of copper (1.6, 3.2, or 6.4 kgm-3, as CuO), air-dried, then re-treated with propiconazole in a light organic solvent at 0.07, 0.3, or 0.7 kgm-3 retentions. In a separate study, SYP field stakes were treated with three levels of ACC to give 6.7, 13.4 or 29 kgm-3 retentions, or the same ACC levels plus citric acid at 38% of the CuO level. These ground-contact stakes were installed at a test plot which has copper tolerant fungi, and inspected regularly for fungal and termite degradation. At the most recent inspection, the copper azole stakes had been exposed for 118 months and the copper citrate stakes for 100 months. For the copper azole stakes, copper alone was only effective at the highest copper retention (10 kgm-3, CuO basis). In contrast, the copper azole-treated stakes were adequately protected with 1.6 kgm-3 CuO and the highest (0.7 kgm-3) level of propiconazole, or 3.2 kgm-3 CuO and 0.3 or 0.7 kgm-3 propiconazole, or 6.4 kgm-3 CuO and 0.07 kgm-3 (or greater) propiconazole. For the copper citrate stakes, stakes treated with copper alone performed slightly better at all three retentions than the copper:citrate-treated stakes. We conclude that the co-addition of propiconazole provides increased protection against copper tolerant fungi and other wood-destroying organisms, with increased azole levels necessary as the copper retention is lowered. In contrast, the co-addition of citric acid did not increase the efficacy of copper.
D D Nicholas, T Schultz

Growth of the copper tolerant brown rot fungus Antrodia vaillantii on different substrates
1995 - IRG/WP 95-10121
In recent years the copper tolerant brown rot fungus Antrodia vaillantii caused severe damages on impregnated wood in ground contact. The pattern of decay gave the impression that impregnated wood was even more severely attacked than unimpregnated. To investigate this question more closely laboratory tests were carried out. In a "choice test" Antrodia vaillantii grew preferably towards CC-impregnated wood. Furthermore, when adding nutrients to the specimens, the mass loss of impregnated wood significantly increased, while the nutrients did not affect the mass loss of the unimpregnated wood. In addition, the temperature tolerance of the fungi increased slightly when growing on impregnated wood. It could also be shown that Antrodia vaillantii reacts with an increased production of oxalic acid to the presence of a CC preservative.
H Leithoff, I Stephan, M-T Lenz, R-D Peek

A possible role of unique TCA cycles in wood-rotting basidiomycetes
2003 - IRG/WP 03-10461
The copper tolerant brown-rot fungus, Fomitopsis palustris, acquires metabolic energy by use of the constitutively-occurring Kornberg’s glyoxylate cycle coordinating with oxalate biosynthesis and glucose oxidation (Erman Munir et al. Proc. Natl. Acad. Sci. USA, (2001) 98, 11126-11130). Furthermore, this fungus does not have the normal TCA cycle, lacking 2-oxoglutarate dehydrogenase which is a key ezyme of the TCA cycle of most living things. This paper reports that most wood decay fungi tested lack 2-oxoglutarate dehydrogenase (ODH) and that much greater activities of glutamate dehydrogenase compensating the absence of ODH were detected from both white- and brown-rot fungi.
E Munir, T Hattori, M Shimada

A Comprehensive Review of Copper as a Biocide, with a Focus on Micronized Copper
2008 - IRG/WP 08-30486
This paper reviews the wood preservative biocide active ingredient copper and delvers into new and previously unpublished data regarding the new micronized formulations which are now in vogue and widespread use in N. America in all residential treated lumber markets. Included in this review is the overall discussion of copper containing formulations used for pressure treated wood used over the last century, and the systems currently in use, worldwide today. Also included in this work, is a long needed thorough review of copper’s mode of action, environmental issues, discussion of copper tolerant fungi issues, leaching and permanence, and efficacy toward a wide array of both fungal and insect species.
M H Freeman, C R McIntyre

The Form of Copper: Does It Really Matter?
2009 - IRG/WP 09-30513
In recent years, several micronized copper formulations for lumber treatment have supplanted the solubilized copper formulations that in turn replaced CCA after its voluntary relabeling in 2004. The micronized or dispersed copper systems use finely ground but solid copper particles and deposit those particles within the wood framework. In contrast, copper in the soluble formulations is relatively mobile and available to react with various wood sites. However, this mobility can also lead to depletion from the wood. This paper explores whether or not the different “forms” of copper affect efficacy of the copper based systems.
C R McIntyre, M H Freeman, T F Shupe, Q Wu, D P Kamdem

Sensitivity to Copper of Basidiospores from Copper Tolerant Fungi: Fomitopsis palustris and Oligoporus placentus
2010 - IRG/WP 10-10707
Copper continues to be an important fungicide in wood preservation. It is the primary component of the preservatives that have replaced chromated copper arsenate for treated wood in residential construction in North America. However, a co-biocide is normally needed to protect against copper tolerant organisms. Previous work has shown that the spores of at least one copper tolerant fungus, Oligoporus placentus, were not very tolerant of copper. This explained the unexpectedly good performance of copper-only preservatives when just exposed to spores and not exposed to mycelium of such fungi. This work was designed to determine if the same was true of another copper-tolerant fungus that produces basidiospores in agar culture. An agar medium bio-assay was used to assess inhibition of basidiospore germination and mycelial growth of Fomitopsis palustris (Berk. et Curt) with O. placentus (Fr.) Gilb. & Ryvarden, as a known reference. The spores of F. palustris and O. placentus had the same copper sensitivity. The basidiospores were sensitive to copper concentrations between 20 and 50 times lower than their corresponding mycelium. These data confirm that spores of copper tolerant fungi are not very tolerant of copper.
C S Woo, P I Morris

Gene expression analysis of a copper-tolerant brown rot fungus on MCQ-treated wood
2011 - IRG/WP 11-10748
Most brown rot fungi are copper-tolerant, which makes them difficult to control with copper-based wood preservatives like MCQ. To better understand what biological processes are regulated, we used our model species, Antrodia radiculosa, to examine expression of genes on MCQ-treated wood. Our hypothesis was genes that decreased copper bioavailability would be up-regulated early, when wood showed no strength loss, while genes that degraded the structural polysaccharides would be up-regulated late, when wood exhibited high strength loss. We used a global profiling strategy called RNA-Seq to record all the genes that were actively being expressed at the two time points. We found 544 differentially expressed gene models. 52 of these gene models had putative functions directly related to oxalate production and polysaccharide degradation. Increased oxalate production at the early time point was caused by up-regulated expression of the following gene models: two pyruvate decarboxylases (3x), one citrate synthase (4x), one isocitrate lyase (8x), one oxaloacetate hydrolase (4x), and four mitochondrial carrier proteins (up to 9x). Up-regulation of oxalate is consistent with the theory that fungi remove copper toxicity by forming insoluble copper oxalate crystals. With respect to the late time point, we found sixteen gene models from at least six different glycoside hydrolase families (GH5, GH10, GH12, GH3, GH61, and GH53) that were highly up-regulated (as much as 23x), along with many sugar transporter genes. Function of the glycoside hydrolases involved cleavage of the -bonds typical of the hemicelluloses and cellulose, which explained the 52% strength loss observed at the late time point. Interestingly, two different sets of gene models for pectin hydrolysis were up-regulated at both early and late time points, suggesting that the pectic substances they targeted were slightly different. These results are significant for wood protection because we have identified the genes that are regulated to uptake sugars, control oxalate levels, and to enzymatically degrade pectin, cellulose, and the hemicelluloses. By knowing these control points, we can rationally develop the next generation of environmentally safe wood preservatives. We also hope to exploit novel brown rot biochemistries for new industries, like biological pretreatment of wood for cellulosic ethanol production.
J D Tang, A Perkins, S V Diehl

Effectiveness of Copper Indicators in Treated Wood Exposed to Copper Tolerant Fungi
2014 - IRG/WP 14-20554
Wood treated with a copper based wood preservative will typically turn a green color. While the depth of copper penetration can be readily discerned from the green color of the copper it is standard practice in research and commercial treating plants to make use of a color reagent such as Chrome Azurol S, Rubeanic acid or PAN indicator to reveal the penetration more clearly. When copper treated wood is exposed to copper tolerant fungi discoloration of the original green color can occur. Reactivity of the treated wood with the color reagents can also be impaired. In this paper, the effectiveness of copper color indicators in detecting copper in wood attacked by copper tolerant brown rot fungi at early and late stages of decay was evaluated. Neither Chrome Azurol S nor PAN indicator could detect copper in the area where incipient and severe decay took place, even when chemical analysis showed significant levels of copper in these areas. Rubeanic acid was the only indicator which provided positive identification of copper in these samples. An FTIR study demonstrated that the loss of green color in copper treated wood by copper tolerant fungal attack is closely related to the formation of copper oxalate. The finding supports the theory that copper oxalate detoxifies copper and acts as a precursor for decay since a significant amount of copper oxalate was found in the area with discoloration but no visual decay, as well as in the area with severe decay. The results from this study suggest that the ineffectiveness of Chrome Azurol S and PAN indicators may be due to their inability to replace oxalate ion to form the colored complex with copper.
L Jin, K Brown, A Zahora, K Archer

Untreated and copper-treated wood soaked in sodium oxalate: Effects of decay by copper-tolerant and copper-sensitive fungi
2017 - IRG/WP 17-10888
Copper is widely used as the primary component in wood protectants because it demonstrates a broad range of biocidal properties. However, a key concern with using copper in wood preservative formulations is the possibility for brown-rot basidiomycetes to resist the toxic effect. Many brown-rot basidiomycetes have evolved mechanisms, like the production and accumulation of oxalate, which helps these fungi to tolerate copper-treated wood by detoxifying copper. The purpose of this study was to determine if untreated wood and copper-treated wood soaked in sodium oxalate influenced the rate of decay by brown-rot basidiomycete fungi. Both untreated and 1.2 % ammoniacal copper citrate-treated test blocks were subjected to an additional sodium oxalate treatment via two soaking methods (ten minute and two hour). Test blocks were exposed to two Fibroporia radiculosa isolates (FP-90848-T and L-9414-SP) and one isolate of Gloeophyllum trabeum isolate (MAD 617) and evaluated for weight loss at four and eight weeks. Decay was between 40-43% weight loss at week eight for F. radiculosa L-9414-SP when untreated blocks were soaked with sodium oxalate. F. radiculosa L-9414-SP demonstrated decay of 38% at week eight when copper citrate-treated blocks were soaked with sodium oxalate. F. radiculosa FP-90848-T decay was much lower for untreated blocks soaked with sodium oxalate (12-13%) and only slightly higher on copper-treated blocks soaked with sodium oxalate (19%) by week eight. G. trabeum MAD 617 decay was between 40-46% when untreated blocks were soaked with sodium oxalate. G. trabeum was unable to successfully decay the copper citrate-treated blocks soaked with sodium oxalate (0.5%) by week eight. The copper-tolerant and copper-intolerant test fungi used in this study demonstrated no major increase in decay when untreated and copper-treated wood was amended with oxalate.
K M Ohno, G T Kirker, A B Bishell, C A Clausen

Sequestration of copper ions by the extracellular mucilaginous material (ECMM) of two wood rotting basidiomycetes
2004 - IRG/WP 04-10533
The radial growth rate of colonies originating from either whole or ECMM-free inocula of Coriolus versicolor was investigated. The presence of ECMM allowed colonies to maintain higher growth rates than those form ECMM-free inocula up to 2 mM CuSO4 in the medium. The ECMM of C. versicolor and G. trabeum was able to reduce the diffusion of copper ions in solution. The ‘raw’ ECMM of both fungi had a greater ability to reduce the diffusion of copper ions than ECMM which had been subject to dialysis to remove soluble, low molecular weight components. The ‘insoluble’ fraction of ECMM for both species was more effective than the ‘soluble’ fraction at reducing the diffusion of copper ions. It is concluded that ECMM confers some protection to hyphae against the toxic effects of copper ions on growth in vivo and that this due to the binding of copper ions to both the polysaccharide and to low molecular weight components of the ECMM
D Vesentini, D J Dickinson, R J Murphy

Influence of different fixation and ageing procedures on the leaching behaviour of copper from selected wood preservatives in laboratory trials
2003 - IRG/WP 03-20264
The paper focuses on the role of different parameters, such as fixation, sample size, wood species, and leaching in internationally standardized ageing procedures for wood preservatives from Europe, Japan and the United States. The leaching protocols used were EN 84, JIS K 1571 and AWPA E11 protocols. The wood species were Scots pine, Sugi and Southern Yellow Pine respectively. Three types of commercially important copper-based wood preservatives were used as model formulations, namely copper/copper-HDO, ammoniacal copper/quat and CCA. The most important factors determining the extent of copper leaching in the different lab trials were the sample size (volume/surface ratio) and the fixation conditions prior to leaching. On the other hand, the wood species and the leaching protocol itself were found to have only minor influence on the copper leaching rate in the test methods included in this study.
J Habicht, D Häntzschel, J Wittenzellner

International collaborative laboratory comparison of two wood preservatives against subterranean termites: Third update and first report
1996 - IRG/WP 96-10174
At the 24th annual meeting of IRG in Orlando, USA, in May 1993 an international subterranean termite laboratory bioassay to compare the various preferred termite protocols used by IRG termitologists was initiated. The author was nominated to co-ordinate this comparative laboratory evaluation of two wood preservatives, copper-chrome-arsenic (CCA) and copper naphthenate (Cu-Na) against the subterranean termites used as test termites in Australia, France, Japan, Thailand, United Kingdom and the Unites States of America. Solutions of these two wood preservatives were prepared and impregnated into Pinus radiata wood blocks to obtain loading of 0.0, 0.5, 1.0, 2.0 and 4.0 kg/m³ respectively. All preservative treatments were carried out at the Division of Forestry and Forest Products in Melbourne. The treated specimens were dispatched to the participating researchers who subjected these specimens to attack by their test termite species, and have now returned the specimens to Melbourne. This paper reports the amount of wood consumed and the mean mass loss (%) on both treated and untreated wood blocks by the termites in the various laboratory bioassays.
J R J French

Types of decay observed in CCA-treated pine posts in horticultural situations in New Zealand
1984 - IRG/WP 1226
The few reported failures of 11-12-year-old horticultural posts in New Zealand in 1982 were caused by brown-rot. A subsequent survey of CCA-treated posts in all the major horticultural areas has revealed decay of many posts. A microscopic examination of these posts has shown decay by brown-rot, white-rot, soft-rot and bacteria. Several types of bacterial decay have been observed.
J A Drysdale, M E Hedley

An investigation of the effects of pre-steaming on the treatment of sawn spruce timber with Celcure A, a copper-chrome-arsenic preservative
1981 - IRG/WP 3150
Difficulties in the treatment of spruce using standard vacuum/pressure techniques with both water-borne and organic solvent preservatives are well known. We have evaluated the influence of steaming on treatability with a waterborne CCA preservative.
C R Coggins

Electrodialytic remediation of creosote and CCA treated timber wastes
2002 - IRG/WP 02-50190
There is a growing concern about the environmental issue of impregnated timber waste management, since an increase in the amount of waste of treated wood is expected over the next decades. Presently, no well-documented treatment technique is yet available for this type of waste. Alternative options concerning the disposal of treated wood are becoming more attractive to study, especially the ones that may promote its re-use. Inside this approach, the electrodialytic process (ED) seems a promising technique for removal of preservative chemicals from treated wood waste. The method uses a direct electric current and its effects in the matrix as the “cleaning agent”, combining the electrokinetic movement (mainly due to electromigration, but also electro-osmosis and electrophoresis), with the principle of electrodialysis. This work reports results from the application of the electrodialytic process to an out-of-service Portuguese creosote and CCA-treated Pinus pinaster Ait. railway sleeper and pole. The behaviour of the process is described and the main results discussed. The average removal rate, estimated in accordance with prEN 12490, for creosote from treated timber waste was around 40 %.. For CCA treated timber waste, experimental conditions that could optimise the process efficiency (e.g. current density, time) were studied. The highest removal rates obtained until now, in our studies, were 93 % of Cu, 95 % of Cr and 99 % of As for sawdust using 2.5 % oxalic acid (w/w) as the assisting agent. For CCA treated wood waste in the form of chips, the best removal rates obtained until now were 84 % of Cu, 91 % of Cr and 97 % of As.
E P Mateus, A B Ribeiro, L Ottosen

Fungicidal activity of some organic solvents, copper carboxylates and their complexes with 2-aminoethanol
1997 - IRG/WP 97-30136
We evaluated the activity of eight organic solvents against wood - rotting fungus Trametes versicolor in order to choose the most appropriate one for rapid screening tests of some copper(II) carboxylates and their adducts with 2-aminoethanol. Their activity against the selected fungus was classified in the following order: chloroform > N,N-dimethylformamide > acetonitrile > methanol > dimethyl sulfoxide > ethanol > acetone. The non-polar white spirit did not dissolve in the growth medium and the results could not be directly compared with the results for other solvents. As an appropriate solvent for screening of the tested copper(II) carboxylates, dimethyl sulfoxide (DMSO) was chosen. Minimal inhibitory concentration against Trametes versicolor of the screened carboxylates was in the concentration range of 1x10-4 to 1x10-3 mol/l. Coordinated amine ligands slightly, and not significantly, decreased fungicidal properties of the tested carboxylates.
M Petric, F Pohleven

Termite resistance of pine wood treated with chromated copper arsenates
1997 - IRG/WP 97-30128
Two four-week, no-choice laboratory tests were performed with CCA-treated southern yellow pine and radiata pine against Formosan subterranean termites, Coptotermes formosanus. CCA retentions as low as 0.05 kg/m3 (0.03 pcf) provided protection from all but light termite attack (rating of 9 on a 10-point visual scale). Similar and consistent light attack on wafers containing retentions as high as 6.4 kg/m3 (0.4 pcf), coupled with complete termite mortality, demonstrates that the mode of action of CCA treatments relies upon toxicity rather than having any repellent effects against termites.
J K Grace

Problems of fixation of CCA-preservatives in palm-wood
1985 - IRG/WP 3338
Palm-wood may be used for posts and poles where it needs proper treatment for long time use. Based on observations by W. Killmann on low CCA-fixation in palm-wood, samples of Jubaea-palm grown in a Greenhouse at Hamburg, have been treated in two different series with a 4% solution of CCA-type B. After 1-16 weeks of storage the blocks were split into sticks of 1-2 mm² and leached. In all series 50% of the chromium and copper content of the individual blocks was leached independent of the time of storage, whereas simultaneously treated pinewood samples showed complete fixation after 4 weeks of storage.
H Willeitner, K Brandt

Field Testing of Copper Carboxylate Preservatives
2003 - IRG/WP 03-30322
This paper details our ongoing experience with field testing of copper naphthenate and other copper carboxylate preservative systems. Results from field stake tests at an AWPA Hazard Zone 4 test site are presented. In general, copper carboxylates made with ‘synthetics’ yielded results equivalent to or only slightly lower than systems with straight nap acids or nap acids amended with synthetic neo acid bottoms.
H M Barnes, M G Sanders, T L Amburgey

The leaching of copper, chrome and arsenate from CCA-impregnated poles stored for ten years in running water
1978 - IRG/WP 3122
There is no evidence to indicate that the chromium and copper components are leached from the outermost 5 mm of sapwood in poles impregnated with Boliden K33 and Tanalith C and stored in running water for ten years. The arsenic component, however, seems to be leached out during the first few months to an extent of about 20% of the initial amount. The leaching time is dependent on the preservative used.
F G Evans

Recent soft-rot research in softwoods and hardwoods
1980 - IRG/WP 1108
The purpose of this paper is to describe briefly the current status of our research on soft-rot fungi. The work to be discussed is still in progress and any results described must be regarded as provisional.
J A Butcher

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