International Research Group (IRG) on Wood Protection
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ItemGelatin encapsulated fumigants for wood fumigations: Current research status(1985)The fumigants chloropicrin (trichloronitromethane) and methylisothiocyanate (MIT) were encapsulated in gelatin as an alternative to liquid fumigant treatments for control of decay fungi in wooden utility poles. Gelatin-encapsulated MIT was stored for over 2 years under dry conditions without significant fumigant leakage. Gelatin encapsulated MIT and chloropicrin were released from capsules when placed in wood above the fiber-saturation point, although capsules were more permeable to MIT than chloropicrin. In field treatments, the addition of small quantities of water along with capsules was sufficient for fumigant release. Encapsulated MIT and chloropicrin treatments effectively reduced decay fungus populations in Douglas-fir utility poles.
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ItemUse of fluorescent-coupled lectins as probes for studying fungal degradation of wood(1986)The ability of the fluorescent-coupled lectins wheat germ agglutin (WGA) and Concanavalin A (Con A) to react with selected Basidiomycetes, Ascomycetes, and Fungi Imperfecti was evaluated using pure cultures of 35 fungi grown on malt extract agar. WGA, which binds specifically to the n-acetylglucosamine residues found in fungal chitin, reacted with nearly all hyaline fungal structures but did not react with dematiaceous (dark) structures. Several reasons are suggested for this variation. Con A, which is specific for a-D-mannosyl and a-D-glucosyl residues, reacted with about one half of the fungi that reacted with WGA. This variation in reactivity may be useful for studying simultaneous degradation by morphologically similar fungi having different lectin specificities. The results indicate that WGA is a useful probe for studying fungal degradation by non-dematiaceous fungi particularly at the early stages of decay.
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ItemThe influence of wood moisture content on the fungitoxicity of methylisothiocyanate in Douglas fir heartwood(1987)The fumigant methylisothiocyanate (MIT) effectively controls decay fungi in large wood structures, but the influence of environmental factors on its performance are not well understood. Experiments found wood moisture content to greatly influence the fungitoxicity and sorption of MIT in Douglas fir heartwood. At constant, low MIT vapor concentrations (less than 1 µg/cc air), wood at 10% MC bound 5 times more MIT, but required 4 times the exposure period to control the decay fungus Poria carbonica, than similarly treated wood above the fiber saturation point. Sorption of MIT to wood was strongly influenced by wood moisture content, but was not substantially influenced by the amount of wood decay. Increasing wood moisture content from 10% to 30% during fumigation resulted in a rapid volatilization of previously bound MIT and a dramatic increase in fumigant fungitoxicity. The increased fungitoxicity of MIT in wet wood may help explain why Vapam (a 32% solution of sodium N-methyldithiocarbamate in water), which decomposes to produce MIT, has performed well as a wood fumigant.
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ItemEffects of air-seasoning on fungal colonization and wood strength of Douglas fir poles(1987)Air seasoning economically reduces the moisture content of Douglas fir poles before pressure treatment with preservatives. Advanced decay in poles in service has resulted when decay fungi (Basidiomycetes) colonized poles during air-seasoning and survived the treatment process. These problems have led to recommendations to severely limit this practice. To determine the role of these fungi in peeled and unpeeled Douglas fir poles during air-seasoning in the Pacific Northwest, we identified many of the fungi involved, measured their effect on wood strength, and studied methods for limiting fungal colonization. Over 90 percent of peeled poles air-dried for more than 1 year contained decay fungi, suggesting that air-seasoning in the Pacific Northwest might pose some hazard; however, no significant strength losses were noted in poles dried 1 to 2 years. Poles seasoned for 3 years began to show significant strength losses, but these strength values fell within suggested design parameters for Douglas fir poles. Although Douglas fir poles are colonized by decay fungi as they dry, our results indicate that these fungi do not cause serious damage for at least 2 years. On the basic of these results, we recommend that poles be air dried no longer than 3 years in the Pacific Northwest. We also emphasize the importance of heating air-seasoned wood adequately during the treatment process to kill any fungi present.
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ItemPenetration and absorption of water-borne preservatives in conifers from the Western United States: A preliminary report(1988)The treatment of most softwoods from the western United States with waterborne chemicals poses a major challenge. Although many of these species are commercially treated with waterbornes, there is considerable debate about their treatability. At present, there is little or no information on the treatability of western wood species with waterborne chemicals. The lack of accurate treatability information related to current practices makes it difficult to improve treatment processes. To develop this information, the heartwood and sapwood of three western wood species were treated using five chemical formulations. Included in these tests were oxide and salt formulations of chromated copper arsenate as well as chromated copper borate. Retentions were measured by gross absorption while penetration was measured using chrome azurol S for copper, cucurmin/salicylic acid for boron, and ammonium molybdate/O-anisidine/stannous chloride for arsenic. The results are discussed in relation to future research directions.
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ItemPreliminary modelling of methylisothiocyanate movement through Douglas fir transmission poles(1988)Methylisothiocyanate is a volatile solid that is the active ingredient of several registered and experimental wood fumigants. Information on the sorption and diffusion of this chemical in Douglas-fir heartwood and sapwood was used to develop a two-dimensional model of fumigant movement within a single horizontal cross-section of a transmission pole. The model indicated that dry wood (14% MC) strongly sorbed MIT, which resulted in lower rates of MIT movement. Conversely, it was predicted that wetter wood (22 or 40% MC) held MIT less strongly and had a more rapid rate of chemical movement. In addition, predictions suggest that the presence of an oil-treated peripheral shell had a strong influence on loss of fumigant from the surface of the pole, but had little effect on concentration which developed in the heartwood zone. The results indicate that MIT movement can be effectively modeled. Further studies are underway to account for longitudinal movement of MIT in the model and to simulate extended time periods.
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ItemFeasibility of using biological control agents to arrest and prevent colonization of Douglas fir and southern pine by decay fungi(1988)The use of microfungi to control basidiomycetous decay has been evaluated in Europe for many years, where it has produced mixed results against Lentinus lepideus Fries, the fungus presumed to be the major cause of decay in Scots Pine poles. In the United States, remedial decay control has been largely chemical, with little use of alternative decay control strategies. Increasing restrictions on chemical usage have stimulated renewed interest in biological decay control. In our tests, a European biological control, BinabÒ,was evaluated for its ability to prevent or arrest attack of southern pine sapwood or Douglas fir heartwood by 5 Basidiomycetes commonly isolated from poles in service. Lentinus lepideus was included as a comparison. In general, BinabÒ performed well against Lentinus lepideus and the other brown rotters, but was unable to completely eliminate most of the test fungi. In addition, the biological had little effect on white rot fungi, which are an important component of the microflora in decaying poles. The results suggest that biologicals will not be suitable for remedial decay control without supplemental treatments that favor growth and activity of the biocontrol agent.
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ItemAbility of chloropicrin, Vorlex, or methylisothiocyante to prevent marine borer attack of Douglas fir piling(1989)The preservative-treated shell around Douglas-fir piling is an excellent barrier to attack by marine borers; however, damage to this shell can permit marine borer attack. The feasibility of using fumigants to enhance piling performance was examined by exposing fumigant-treated Douglas-fir sections in marine waters off Newport, OR, or Port Hueneme, CA. The piling were inspected annually and increment cores were removed for chemical assays. Fumigant treatment protected the exposed, untreated wood at the end of the pile for the first year, but marine borer activity generally increased after an additional year of exposure. The fumigants appeared to be most effective against shipworm attack. Chemical levels were generally lowest near the attacked region. Fumigant treatment does not appear to be a long-term solution for preventing marine borer attack of untreated wood exposed during construction or usage; however, the treatment does provide short-term protection and may have some use in ports where a regular maintenance program would insure that damage to treated wood was repaired within one year.
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ItemBorates as wood preserving compounds: The status of research in the United States(1989)This paper describes the extensive, on-going cooperative research effort among government and university research laboratories and industry to fully evaluate the potential for borates as wood preservatives in the United States. Research is discussed in terms of laboratory evaluations, field testing and mill trials, pilot plant pressure treatment studies, and remedial treatments. Future research plans are also presented.
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ItemThe use of fumigants for controlling decay of wood: a review of their efficacy and safety(1989)Volatile agricultural chemicals (fumigants) such as chloropicrin (trichloronitromethane) and sodium n-methyldithiocarbamate have been used in the United States for controlling internal decay of large dimension wood products for over 20 years. This usage has been concentrated in the electric utility industry, but fumigants are increasingly applied to protect bridge timbers, marine piling, and even living trees. This document will review the characteristics of fumigants in relation to other available chemicals, particularly the water-soluble pastes that are commonly employed in Europe. Studies to improve the handling safety of fumigants and future research needs will also be addressed.