Administrative Report Or Publication
 

Conserving energy by safe environmentally acceptable practices in maintaining and procuring transmission poles: third annual report ; June 1983

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  • ABSTRACT Improved Fumigants After 13 years, chioropicrin, methylisothiocyanate (MIT), Vapam, and Vorlex continue to effectively control internal decay of pressure-treated Douglas-fir transmission poles. The estimated retreating schedules for application of these fumigants to treated wood may be as long as 10 years for Vapam and 15 years for the others. The close-tube bioassay, developed during this research, has proven to be an effective method for determining the persistence of these fumigants in wood and should help in determining when fumigant-treated poles should be retreated. The use of gelatin to encapsulate MIT for wood treatment was ideal because the capsules did not react with MIT, were MIT impermeable when dry, permitting prolonged storage without significant fumigant loss, and readily released MIT when moistened in the wood. Although release of encapsulated MIT in the wood was enhanced by small amounts of water, excess moisture appeared to hinder MIT diffusion into wood. Assays of Vapam treated wood show that the amount of MIT released by breakdown of Vapam is significantly lower than the expected theoretical yield from this fumigant. Encapsulated MIT reduced the decay fungus population in poles in service more effectively than applications of Vapam. The effectiveness of a fumigant in controlling decay may be expressed as the product of the fumigant concentration (C) and the time (T) the decay fungus is exposed to the fumigant before it succumbs. A higher value indicates a less effective treatment. In wood, the CT value obtained for MIT was two times greater at 20% wood moisture content (MC) than at 40 and 75% MC. Although MIT was least effective at 20% MC, there was more MIT i bound to the wood than at the higher moisture levels. This suggests that the MIT bound to the wood structure may be less effective against decay fungi than the MIT in the air and water in the wood. Although the effectiveness of MIT varied with the wood MC, it was nevertheless still very fungitoxic over a broad range of moisture levels. In chioropicrin treated wood, inhibition of invasion by decay fungi was indicated by the lysis and vacuolation of the fungal hyphae in the wood. Chloropicrin appears to hydrogen bond to wood and may form covalent bonds with phenolic wood extractives and lignin, possibly increasing the persistence of the treatment. Controling decay of cedar sapwood Three waterborne fungicides have been added to the previously selected materials being tested on cedar pole sections at an O.S.U. test site as potential substitutes for the pentachiorophenol in oil treatment currently used. The effectiveness of all treatments will be evaluated later this year using the Aspergillus bioassay and a modified soil block test. The most effective treatments then will be tested on poles in service. Bolt-hole protection Later this year cores will be removed from the control bolt holes to evaluate the extent of natural fungal colonization. If a sufficient level of colonization has occurred, the effectiveness of the various chemical treatments in preventing decay in field-drilled bolt holes in Douglas-fir poles will be evaluated. Detecting decay and estimating residual strength in poles A serological technique for rapid detection of decay fungi was found to cross react with non-decay fungi and thus lackedthe necessary specificity for identifying decay fungi in wood. Additional work is needed to purify the preparations to render them more specific to decay fungi. Measurements of modulus of rupture (MOR), modulus of elasticity (MOE), work to maximum load, specific gravity, radial compression strength (RCS), and Pilodyn pin penetration of sound appearing wood containing decay fungi were not significantly different from the corresponding values for wood from which no decay fungi were isolated. However, tests of poles with more advanced decay did show significant reductions in wood strength properties. Specific gravity alone was not a good predictor of bending strength of wood from decayed poles, but the use of both specific gravity and RCS tests significantly improved the ability to predict the bending strength of these wood samples. Decay of Douglas-fir poles prior to pressure treatment The continued study of the fungal infestation of poles during air seasoning has demonstrated that there is a significant buildup of Poria carbonica, the major pole decay fungus, with time. In general, as air seasoning time increased, decay fungi infested more poles and occupied more wood within each pole. Sampling of freshly cut poles in the forest this past year showed that some contained potential decay fungi prior to reaching the pole yard. Frequent isolation of decay fungus monokaryons throughout the air seasoning period suggests that spores of these fungi were infesting the poles at a relatively constant rate. The ability of the basidiomycetes isolated from these poles to reduce wood strength will be evaluated in rapid tests for toughness by impact breaking and changes in the breaking radius of Douglas-fir test sticks. iv The germination of basidiospores of P. carbonica was studied on culture medium and laboratory techniques are being developed to follow germination on a wood surface under varying environmental conditions to further illucidate their role in the infestation of seasoning wood. Exposure of sterilized pole sections at four Pacific Northwest air seasoning sites for successive 3-month periods has been continued. The dramatic increase in infection during Nov.-Jan. '81 at all locations except Arlington WA, did not reoccur in that same time period during 1982. There was, however, a continuing low level of infection at all sites during the year with a slight peak of infection in May-June '82 in Arlington WA. The results of these tests are currently being computer analyzed to more effectively study the patterns of fungal invasion of wood as influenced by environmental factors.
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