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Effects of chlorothalonil (CTN) and butylated hydroxytoluene (BHT) on microbial communities involved in the deterioration of wood using T-RFLP I: Accelerated laboratory decay study
2006 - IRG/WP 06-20332
The effects of Chlorothalonil (CTN) and Butylated Hydroxy Toluene (BHT) on microbial species diversity in wood and the surrounding soil are being assessed by Terminal Restriction Fragment Length Polymorphism (T-RFLP). CTN was selected as a trial organic wood preservative, and BHT is being evaluated for its synergistic effects with CTN. Results from an accelerated decay test will be presented. The accelerated decay test evaluates the performance of wood preservatives in conditions optimized to promote accelerated microbial degradation. This study is evaluating six retentions in two different soil mixtures (with and without compost), resulting in a total of twelve treatments. Each month, one box (containing three sticks) per treatment was removed to provide thirty-six samples per sampling period. Biomechanical stress testing is being utilized to determine modulus of elasticity (MOE) as a measure of microbial degradation. TRFLP data is being analyzed to determine significant differences in patterns of microbial colonization over time due to wood preservative treatment in southern yellow pine (SYP) both in and out of soil contact. Soil samples have also been collected to observe changes in soil microbial community due to contact with preservative treated wood. Wood preservative retention is being analyzed using HPLC. Initial results show decreases in fungal and bacterial phylotype diversity for both soil contact and non-soil contact portions of preservative treated SYP wood samples compared to untreated controls. Characterization of these pattern shifts will provide a better understanding of the biology and ecology of wood decay microorganisms, the effects of biocides on the microbial community in treated wood and in the soil, and the effects on microbes on biocide breakdown and wood failure.
G T Kirker, M L Prewitt, S V Diehl

Effects of chlorothalonil (CTN) and butylated hydroxytoluene (BHT) on microbial communities involved in the deterioration of wood using T-RFLP II: Results from field studies
2007 - IRG/WP 07-30429
The effects of Chlorothalonil (CTN) and Butylated Hydroxytoluene (BHT) on microbial species diversity in wood and the surrounding soil are being assessed by Terminal Restriction Fragment Length Polymorphism (T-RFLP). CTN was selected as a trial organic wood preservative, and the non-biocidal BHT was evaluated for its synergistic effects with CTN. ACQ-C was a positive control and untreated SYP stakes were negative controls. Tests were installed at two separate field sites in MS that represent two different AWPA hazard zones. Samples were taken every 3 months over a 15 month period and visually evaluated for termite attack and decay. Samples were processed and whole genomic DNA was extracted for molecular analyses. Upon initial amplification of DNA using both specific and general primers, the presence or absence of target fungi was confirmed using gel electrophoresis. We are currently using T-RFLP to analyze the patterns of microbial colonization over time and in response to external stimuli (i.e., wood preservative treatment) to identify potential shifts in microbial community. Preliminary results indicate that the presence of non-basidiomycete fungi (i.e. molds, stains, and soft rots) are uniformly distributed throughout the samples regardless of treatment, while basidiomycetes are less common and severe decreases in overall basidiomycete populations occurred during periods of drought at both test sites.
G T Kirker, M L Prewitt, S V Diehl

A hypothesis on a second non-biocidal property of wood extractives, in addition to toxicity, that affects termite behavior and mortality
2008 - IRG/WP 08-10638
While it is has long been recognized that heartwood extractives affect termite behavior, the exact cause and relationship between total extractives, extractive types, and termite resistance remains unclear. Generally, researchers have proposed that the extractives are toxic and/or repel termites. We propose, based on the well known fact that many extractives have excellent antioxidant properties in addition to some termite toxicity, that: 1) the antioxidant properties of wood extractives interfere with the termite and symbiotic microbial digestion of lignocellulose; 2) thus, over time termites have learned to recognize and avoid wood with high levels of antioxidants; and 3) consequently, termites will also avoid wood treated with artificial and nontoxic antioxidants. Use of an artificial and nontoxic antioxidant will allow one to definitively test our hypothesis, while tests with natural extractives would be confounded by natural extractives often having both toxicity and antioxidant properties. We conducted some initial tests employing a man-made and benign antioxidant, BHT. In outdoor field trials, ground-contact stakes treated with only the antioxidant had less termite degradation than the control stakes at up to three years of exposure. An initial termite choice experiment using Reticulitermes flavipes Kollar (Eastern subterranean termite) was run with an untreated and 1- or 3%-BHT treated wafer in each jar, along with control jars that contained two untreated wafers. No termite feeding occurred on any of the BHT-treated wafers, indicting that the non-biocidal antioxidant was a strong feeding repellent. Furthermore, while only about 2% termite mortality occurred in the jars that contained two untreated wafers, in every jar that had an untreated wafer and a second BHT-treated wafer 100% mortality occurred. Recent no-choice laboratory tests with two subterranean termite species, R. flavipes and Coptotermes formosanus Shiraki (Formosan subterranean termite), and an exterior test with BHT-treated wood with Formosan termites, confirmed our initial results.
T P Schultz, K Ragon, D D Nicholas

Synergistic combination of an antioxidant and wood preservative: a preliminary study
1998 - IRG/WP 98-30172
We previously proposed that extractives in highly durable angiosperm heartwood may protect wood against white-rot fungal colonization and subsequent degradation by a dual mechanism: extractives have some fungicidal activity and are also free radical scavengers (antioxidants) and thus interfere with the fungal free radical degradative mechanisms. We tested this hypothesis using the commercial biocide DDAC, which has no antioxidant properties, in laboratory decay tests using angiosperm sapwood and white-rot fungi. When the commercial antioxidant BHT, which has no fungicidal activity, was present a dramatic increase in the efficacy of DDAC was observed. This synergistic effect may have commercial applications.
T Schultz, D D Nicholas, J Minn, K D McMurtrey, T H Fisher

Impact of an Antioxidant on the Efficacy of Quaternary Ammonium Compounds (Quats) and Triazoles – Seven Year Above-Ground Study
2009 - IRG/WP 09-30504
It has been reported that antioxidants have great potential for use with organic biocides in the area of wood protection. This paper demonstrates the impact of a low level of the antioxidant butylated hydroxytoluene (BHT) on the efficacy of quat-based and triazole-based formulations. A seven year lap joint test revealed a positive effect of BHT on the efficacy of quat-based formulations, especially at the low quat retention. The incorporation of BHT in a propiconazole-based system, however, showed an unexpected negative antioxidant effect at all levels tested. For tebuconazole- and cyproconazole-based formulations, the antioxidant effect on efficacy is slightly positive but insignificant. The influence of BHT on efficacy appears to diminish with increased active retentions in wood for both quat-based and triazole-based formulations, and in fact yields an adverse efficacy impact at high active retention levels. It is hypothesized that a larger amount of BHT is needed at high active retention levels to ensure the positive antioxidant effect. In addition, wood treated with BHT only showed slight protection for fungal decay, while the untreated controls exhibited severe decay with numerous failures.
Xiao Jiang, D Biro, W Holcombe

Effect of an antioxidant on the efficacy of organic wood preservatives in an accelerated soil contact decay test
2012 - IRG/WP 12-30583
In comparison to inorganic wood preservatives, organic biocides in transient carriers are considerably less effective when the treated wood is exposed to soil contact. Various oils are used in some formulations with pentachlorophenol to improve the efficacy. However, use of these oils imparts unacceptable properties to products used in residential applications. Consequently, there is a need to develop additives other than heavy oils that improve the performance of organic biocides as wood preservatives. In this study the possibility of using the benign antioxidant BHT as a non-biocidal additive to improve the performance of wood treated with isothiazolone and azoles was investigated. The treated wood with and without BHT was exposed to unsterile soil and monitored for decay by dynamic MOE. It was found that the efficacy of both preservative systems was enhanced when BHT was added to the formulations. The use of Dynamic MOE to evaluate the progression of wood decay appears to be far superior to visual ratings.
D D Nicholas, J Shi, T P Schultz, L Sites

Influence of selected additives on organic fungicides for control of bamboo mold fungi
2013 - IRG/WP 13-30626
In order to assess the long-term efficacy of supplemented organic fungicides in outdoor applications, additives - including the antioxidant butylated hydroxytoluene (BHT) and a UV absorber and free radical scavenger benzotriazole (BTA), were selected to mix with the fungicides propiconazole or tebuconazole. Freshly cut samples from four-year old bamboo stems were treated with combinations of the chemicals and biocides and were field-tested for mold growth over a24-weekperiod. Results showed that BHT greatly enhanced the effectiveness of tebuconazole against mold fungi, while it had little effect on mold colonization when combined with propiconazole. BTA reduced the mold resistance of tebuconazole, but greatly promoted the inhibition of mold by propiconazole. The effect of BHT and BTA appeared to enhance the mold resistance of both tebuconazole and propiconazole, but not necessarily when they were combined together.
Sun Fangli, B Goodell, Chen Anliang, Bao Binfu, Zhang Shaoyong