Administrative Report Or Publication


Conserving energy by environmentally acceptable practices in maintaining and procuring transmission poles for long service ; August 1988 Public Deposited

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  • The eighth annual report details continued progress on each of the five objectives. In this year's report, Objectives II and III from previous reports have been combined to reflect the similarity of each effort. Improved fumigants: The previously established field trials continue to demonstrate the superior performance of both chioropicrin and Vorlex after 18 years in poles and 13 years in piling. In addition, solid methylisothiocyanate (MIT) continues to protect Douglas-fir poles in a manner similar to Vorlex. Along with evaluations of existing registered formulations, we continue to explore the use of novel solid fumigants for their ability to arrest decay in Douglas-fir heartwood. Laboratory studies indicate that both Mylone and sodium n-methyldithiocarbamate (NaMDC) can be pelletized to improve handling safety. Previous studies indicate that the rate of decomposition to produce MIT is often too slow for effective fungal control, but the incorporation of certain buffers or metallic salts can alter the rate and characteristics of chemical decomposition. In our tests, the levels of chemical release varied with PH; however, complete fungal control was not achieved. Further studies are underway to determine if other conditions can alter the rate of MIT production by these compounds. Both chemicals are registered for other, nonfood uses and should be registerable for application to wood. Efforts to better understand the properties of MIT, the major fungitoxic product of both Vorlex and Vapam, are also continuing. These efforts have led to the development of a preliminary model to describe fumigant movement through Douglas-fir heartwood. The goal of this work is optimize treatment dosage and application patterns for various pole sizes. In addition to the more theoretical studies, we are continuing our efforts to determine the ability of fumigants to control decay fungi in poles containing large decay voids and to determine the levels of volatile emissions from fumigant treated wood. Field treatment: The field tests to evaluate potential replacements for pentachlorophenol (penta) treatment of western redcedar sapwood were evaluated after 7 years using the Aspergillus bioassay. The results indicate that residual levels of chemical were detectable in the penta treatments, but the remaining test chemicals exhibited little evidence of residual fungitoxicity. Further decay tests are planned on material removed from these pole sections. In addition to the pole sections, the small-scale test blocks were also evaluated using the Aspergillus bioassay. The results indicate that several chemicals remained in the wood at fungitoxic levels after one year of accelerated weathering. Further decay tests are also planned on these samples. The bolt hole study is now in its seventh year and the incidence of decay fungi in the test poles remains low. Variations in incidence from year to year have made it difficult to draw any useful conclusions from this study. To overcome this problem, a second test has been established which accelerates leaching and evaluates the ability of a test fungus to invade the field drilled bolt hole to cause wood weight loss. Decay detection and residual strength: We continue to evaluate the use of lectins for detecting fungal colonization at the early stages. This past year, we completed a comparison of colonization by three common decay fungi over a 12 week period. The search for small-scale methods for estimating residual strength is also continuing. Longitudinal compression measurements were used to determine residual strength of a pole involved in an automobile accident. ii Finally, we have completed portions of a study to determine the effects of fungal colonization on wood strength. Four fungi, Poria carbonica, Poria placenta, Peniophora spp., and Haematostereum sanguinolentum were evaluated in this study. Results with P. carbonica and Peniophora spp. indicate strength effects lag behind fungal colony development in small beams. These results were similar to previous field studies and indicate that air-seasoning for 2 to 3 years should not produce significant strength losses. Further studies with these fungi are underway. Initiation of decay in air-seasoning Douglas-fir: While the air-seasoning studies are now completed, we are continuing to evaluate the data from these tests. A detailed examination of the three year decay development study indicates that several fungi were typically found only in the heartwood or sapwood zones of the pole sections. In addition, the fungal flora at the four seasoning sites varied widely, with the greatest deviation occurring at the Oroville, CA. This site has the driest and warmest conditions, and would appear to be best site for seasoning. A detailed discussion of isolation frequency by position is presented for the eleven most common basidiomycetes. Studies to prevent colonization by basidiomycetes during air-seasoning are also continuing using polyborate dips or sprays. Sodium octaborate tetrahydrate appears to reduce the level of colonization after one year of air-seasoning at both Oroville and Corvallis, OR. Dipping shortly after peeling appeared to produce the best results, although spraying at regular intervals also had some effect on colonization. This study will continue for an additional two years. Determining the ability of existing pressure treatment cycles to eliminate fungi which colonize Douglas-fir poles during air-seasoning also remains a high priority. Only a few additional schedules were examined during iv the past year, but efforts to develop more realistic heating curves are under way. In addition, several questions concerning the accuracy of the existing data were answered. Additional studies using the Cellon process and the longer steaming period for the ammoniacal copper zinc arsenate treatments are planned in the coming year. While sterilization during preservative treatment is an important factor in pole longevity, questions have also arisen concerning the storage of poles for long periods after treatment. A survey of poles which were treated with creosote, pentachiorophenol, chromated copper arsenate, and ammoniacal copper arsenate prior to storage for one to 15 years was conducted. While colonization varied widely between sites, the results indicated that storage of poles for long periods substantially increased the risk that the pole would be placed in service with an active decay fungus established somewhere along its length. Several suggestions are made for remedying this situation. Effect of microfunqi on Douglas-fir poles: A study was conducted to determine the effect of microfungi which commonly colonize fumigant treated Douglas-fir heartwood on the ability of P. carbonica and P. placenta to cause wood weight loss in fumigant treated wood. The results indicate that several isolates were associated with reduced weight losses by these fungi. The decreased weight losses suggest that the microfungi could be colonizing fumigant treated poles prior to the basidiomycetes and, once there, could help prevent reinvasion. This scheme may help explain the remarkable protection provided by fumigant treatment. Further studies are underway to explore this possibility.
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