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Conserving energy by safe and environmentally acceptable practices in maintaining and procuring transmission poles ; August 1984 Public Deposited

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  • After 14 years, chloropicrin, Vapam and Vorlex continue to effectively control internal decay of pressure-treated Douglas-fir transmission poles, but 6 years after application of methylisothiocyanate (MIT) some poles are becoming reinfested by decay fungi although NIT residues remain high in these poles. The closed-tube bioassay, developed through our research, is an effective method for detecting fumigant persistance, and future studies will aim at determining the actual fumigant concentrations detected in wood by this bioassay. A study of MIT movement through Douglas-fir pole sections following treatment with gelatin encapsulated MIT was completed and results indicate that addition of small quantities of water along with the capsules will give excellent fumigant release and movement into the wood. Decay fungi were virtually eliminated from in service transmission poles 21 months after treatment with gelatin encapsulated MIT near the groundline. In poles treated up to 12 feet above the groundline with encapsulated MIT and chloropicrin, no decay fungi could be isolated 1 year after treatment. Both fumigants were well distributed through the poles and appear to have moved laterally from the treatment holes. One of the goals of our research has been eventual fumigant application to poles at the treatment plant shortly after conventional preservative treatments. This would provide predrilled holes for later fumigant retreatment and would effectively protect the entire i iipole cross section. While the most economical application method would involve incorporating the fumigant treatment holes into the conventional predrilling process, it would also result in preservative treated fumigant holes. Consequently we have initiated studies to determine the influence of creosote and pentachlorophenol on fumigant movement into treated wood. Preliminary results indicate that creosote and P-9 penta base oil slow movement of MIT into wood but do not prevent the build up of fungitoxic concentrations in the wood. The new, pelletized MIT formulation has been evaluated in our laboratory assay for wood fumigants. The results indicate that pelletized MIT is as effective as pure MIT on an active ingredient basis. Since pelletized MIT has many similar application and safety advantages as encapsulated MIT, we intend to further evaluate pellets in poles in service. Cedar Sapwood Decay Control The effectiveness of seventeen chemicals (3 oil-borne, 14 water-borne) for controlling above-ground decay of cedar sapwood was evaluated using a modified soil block test and an Aspergillus bioassay. Pentachlorophenol (10%) in diesel oil, currently used for protecting cedar poles, was markedly superior to all other chemicals evaluated probably because of the increased penetrability of the oil, since penta in water at the same strength did not perform as well. Three other formulations, copper-8-quinolinolate (oil), pentachlorophenol (2% in water), and 3-iodo propynyl butyl carbamate (2% in water), exhibited some residual effectiveness; however, more time is necessary to determine if these chemicals will remain effective. An additional five chemicals will be evaluated this coming spring. iii The persistence of chloropicrin 5 years after treatment in western redcedar was also evaluated using open tube bioassays, closetube bioassays and gas chromatographic determinations. The open tube bioassay indicated that chioropicrin still effectively limited growth of the assay fungus, P. placenta. Similarly, closed tube bioassays indicated strong inhibition in the pole interior and lower inhibitions near the surface. Extraction/gas chromatographic procedures detected chloropicrin in all cores examined with the highest concentrations towards the pole interior. Chioropicrin concentration did not correlate with closed tube results, suggesting that these tests are measuring different fumigant properties. The results indicate that chloropicrin should be an effective treatment for preventing cedarbutt rot and may provide some protection to pole sapwood. Bolt Holes Control poles for the bolt hole protection study were again sampled and insufficient decay was found in these poles to warrant evaluation of the various decay prevention treatments. We will reevaluate the control poles this summer. Detecting decay and estimating residual strength in poles An infrared spectrophotometric method of analyzing warm water extracts of decayed and non-decay wood was evaluated with a number of brown and white rot fungi. Brown rot was highly correlated with absorption peaks produced at wavelength 17201cm. Work is now underway to identify this peak to determine if less involved detection methods might be employed. iv Fluorescent labeled lectins, which have high specificity for selected carbohydrates, were also evaluated as potential fungal indicators. Of the lectins tested, wheat germ agglutinin appears the most promising since it strongly reacted with chitin in the fungal cell wall, making decay hyphae visible at very early stages of decay. Evaluation of Douglas-fir beams air-seasoned for 1 or 2 years using Pilodyn pin penetration, longitudinal compression, radial compression, bending and culturing indicated that, while there is a well established fungal flora in the wood, this flora has not yet affected strength. These tests will be performed on the 3 year airseasoned beams this coming year. Of the strength tests employed, longitudinal compression appears promising for estimating pole bending strength and we intend to further evaluate this method. As a second phase of this evaluation, the effect of moisture content on Pilodyn pin penetration was examined. This information is necessary since pin penetration varies with moisture content and must be corrected to compare values from different poles. Pin penetration increased with increasing moisture content up to fiber saturation and stabilized above this point. The moisture content at 0.5 inches was highly correlated with pin penetration, and this depth might be a convenient standard measuring point. En a new phase of the project, preliminary acoustic testing was begun using small beams from poles at varying stages of decay. These beams were sonically evaluated and then loaded to failure in three point bending tests. Sonic evaluation was highly correlated with NOR; however, much more testing will be necessary before such an apparatus can be applied to posts or poles. V Initiation of decay in Douglas-fir poles prior to pressure treatment The ability of basidiomycetes isolated from air-seasoning poles to reduce wood strength was evaluated in rapid tests for toughness by impact bending and changes in the breaking radius of Douglas-fir test wafers. Although some fungi behaved differently in the two tests, the test correlations were relatively high (r2 = O.78S). Of 26 basidiomycetous species evaluated, Poria placenta, P. carbonica, P. xantha and Crustoderma dryinum most rapidly decayed Douglas-fir heartwood, but at least one isolate of most of the other species tested significantly reduced toughness. While the wood decaying ability of each fungus is important, the frequency of isolation also must be considered when determining the overall importance of a species. To determine the influence of wood temperature and moisture content on establishment of P. carbonica in Douglas-fir heartwood, a method was developed for direct observation of germinating spores on wood. In this test, chiamydospores and basidiospores failed to germinate or colonize wood at moisture content below fiber saturation suggesting that free water is necessary for infection. Chiamydospores germinated most readily and colonized wood at 22°C, while germination was significantly lower and the fungus failed to become established in wood at 5 or 35°C. Similar temperature responses were obtained with basidiospores although these spores failed to germinate at 5 and 35°C. Nevertheless, basidiospores may remain viable and retain the potential to establish colonies once conditions become more favorable. vi Exposure of sterilized pole sections at four Pacific Northwest air-seasoning sites for successive 3-month periods showed a significant increase in basidiomycete isolation frequency for the period Nov. '81-Jan.'82. Furthermore, the frequency increased from the northern to the southern most site. Detailed study of the site weather patterns strongly suggests that increased basidiomycetous infection can be related to number of days with measurable rain fall and temperatures conducive to fungal growth. During the other periods studied, temperature or precipitation conditions were unfavorable for infection and pole section moisture contents fell below fiber saturation. This in turn limited spore germination and fungal colonization of the wood. About 30 different basidiomycetous species have been identified from isolates cultured from sterilized pole sections exposed at the four sites. In general, the species were the same as those isolated form air-seasoning poles although there were some significant differences between the species obtained from the different sites. The frequency of P. placenta mono- and dikaryons was particularly high with monokaryons more abundant at three of the four locations. Individual species exhibited distinct colonization patterns from different pole zones. For example, P. placenta was isolated most frequently from heartwood exposed at the pole ends while Peniophora spp. and llaemotostereum sanguinolentum were recovered most frequently from the upper surfaces of the pole sections. vii Preventing infection of poles by decay fungi during air-seasoning Pole sections treated with ammonium bifluoride (NH4HF2) or gelatin encapsulated MIT and chioropicrin were extensively sampled after air seasoning to determine the influence of these chemicals on wood colonization by decay fungi. Preliminary results indicate that after 2 years NH4HF2 and the fumigants significantly reduced basidiomycetous colonization of sterile wood. Surface Decay Poles treated with Vapam 14 years ago were extensively cored, the cores were cultured and the resulting fungi were identified to evaluate the fungal flora of fumigant treated wood. A well developed fungal flora was identified that differed from that found in nonfumigant treated wood. These fungi will be further evaluated to determine their role in fumigant effectiveness.
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