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Conserving energy by safe and environmentally acceptable practices in maintaining and procuring transmission poles for long service ; June 1982 Public Deposited

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  • ABSTRACT Improved Fumigants Chioropicrin, Vorlex and Vapam continue to control internal decay of pressure-treated Douglas-fir poles 12 years after application. Fungitoxic quantities of chloropicrin are present in the wood as high as 2.4 m (8 feet) above the groundline. Solid methylisothiocyanate (MIT), which goes directly to a vapor, is somewhat more effective in controlling decay than is Vorlex MIT is the active ingredient of Vorlex. Gelatin capsules containing chioropicrin or MIT offer new opportunities for improved fumigation of poles. MIT is readily released in moist wood, but chioropicrin capsules require wetting after they have been placed in the wood or they must be mechanically ruptured for maximum effectiveness. Although chioropicrin and MIT are adsorbed by wood after adequate aeration, the fumigant-treated wood may be attacked by decay fungi. Encapsulated MIT, is being compared to Vapam in pressure-treated Douglasfir transmission poles near Buffalo, NY. Controlling decay of cedar sapwood Six decay fungi have been identif led from sapwood and three from heartwood, of decay in cedar poles. Five waterborne chemicals have been selected as potential substitutes for the 10% pentachlorophenol-diesel oil solution currently used to spray cedar sapwood. Of these, 3-iodo-2-propynyl-butylcarbamate equalled or exceeded the pentachlorophenol solution in effectiveness at depths to 15 mm in the endgrain of weathered blocks. i ii Seven chemicals judged to be the most promising were applied to cedar poles at the Northwest Forest Genetics Center last fall. Other promising chemicals detected by a bioassay will be applied to poles this summer. Bolt-hole protection Twenty-eight Douglas-fir poles 18 feet long were Boulton dried in a pentachlorophenol-heavy petroleum solution, drilled with 8 alternating 3/4-inch and 1-inch diameter holes in a spiral pattern and installed at the Northwest Forest Genetics Center. Dry or liquid waterborne chemicals with low mammalian toxicity or a 10% pentachlorophenol solution were applied in the holes before the bolts were inserted. Patox washers between the pole and crossarm attachment also are being tested. Cores will be removed below unprotected bolt holes in control poles and cultured for decay fungi as a guide for removal of cores below protected bolt holes. Detecting decay and estimating residual strength. Testing plugs from Douglas-fir poles for radial compression strength (RCS) was more promising than chemical tests that coloreçl the wood or a needle-scratch test for detecting early decay. RCS, which measures the strength of the weakest springwood layer was highly correlated with weight loss caused by Poria placenta, an important brown-rotter of Douglas-fir poles. RCS losses were detected before weight losses could be measured. Sapwood was lower in RCS than heartwood, probably because of differences in extractive content of cell walls. Infrared spectographic analysis of dried warm water extracts from wood beams decayed to low weight losses and tested in bending is being evaluated as a means of detecting early stages of decay that might cause significant strength losses. iii As a means of estimating residual strength of poles, RCS values, bending strength properties, toughness and sonic properties of small beams cut from pole sections exposed at the four Northwest air-seasoning sites are being evaluated. Decay of Douglas-fir poles prior to pressure treatment Fourteen cores were removed from 229 unpeeled poles and 752 peeled poles stored in seasoning yards from 0 to over 24 months and cultured for fungi. About 50% of the probable decay fungi isolated from the cores have been identified. Atleast 30 of the unpeeled poles (13%) contained decay fungi. The incidence of decay fungi, especially Poria carbonica, increases significantly as the air seasoning time is prolonged. This summer cores will be removed from freshly cut poles in the forest and from additional poles during air seasoning, especially those seasoned for over 1 year. Laboratory studies indicate that spores and fungal fragments, alone or attached to soil particles and air borne, play an important role in the infection of poles. Exposure of sterilized pole sections at the four Northwest air seasoning sites for successive 3-month periods indicates that infection increases dramatically during the November-January period at three sites. borne spores appear to play an important role in the infection
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