1992 EXTENSION DEMONSTRATION AND RESEARCH REPORT COOPERATIVE EXTENSION SERVICE UNIVERSITY OF ALASKA FAIRBANKS FAIRBANKS, ALASKA

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1 1992 EXTENSION DEMONSTRATION AND RESEARCH REPORT COOPERATIVE EXTENSION SERVICE UNIVERSITY OF ALASKA FAIRBANKS FAIRBANKS, ALASKA Ken Krieg Editor February, 1993

2 SERVICE LIFE OF PRESERVATIVE TREATED POSTS USING ALASKA TREE SPECIES by Patrick Mayer, Research Assistant, Agricultural & Forestry Experiment Station, Palmer, AK, George Sampson, Research Forester, U.S. Forest Service, Pacific Northwest Research Station, Institute of Northern Forestry, Fairbanks, AK. Tony Gasbarro, Extension Forester, University of Alaska Fairbanks Lee Allen, Retired Agricultural Engineer, Agriculture and Forestry Experiment Station, Palmer, AK LOCATION: FUNDING SOURCE: OBJECTIVE: Agriculture and Forestry Experiment Station Palmer, AK. Agriculture and Forestry Experiment Station To determine the effectiveness of several different methods for treating posts on a small scale INTRODUCTION: There is interest in treating products from Alaska tree species with preservatives to reduce dependence on imported preservative treated products. This is particularly true for treated fence posts which could be produced on a small scale by Alaskan farmers and ranchers. A number of different methods have been used to treat wood with preservatives on a small scale. Methods specifically considered for Alaska include: double diffusion, capillary pull up, soaking in a solution, and soil treatment with dry chemicals at ground line. METHODS: This study was initiated in 1954 to test the technical feasibility of some of these methods. Fence posts to be treated were cut from balsam poplar (Populus balsamifera L.), paper birch (Betula papyrifera Marsh), white spruce (Picea glauca [Moench] Voss) and quaking aspen (Populus tremuloides Michx,), The posts ranged from three to six inches in top diameter and were seven feet long, Six treatments and two controls were included in the study. The six treatments were: cold soaking in solution, capillary pull up using autumn cut and capillary pull up using spring cut trees, brushed on creosote, copper sulfate in soil, and double-diffusion. One control consisted of untreated green unpeeled posts, and the other untreated green peeled posts (Table 1). Twelve posts of each species were used*for each treatment. Some treatments were placed at regular intervals in a fence row, while other treatments were placed in grid formation at a single site. Due to the nonquantiflable site differences presented by the different planting treatments, statistical analysis for treatment comparison was not undertaken. However, this information is certainly indicative of the relative performance of the treatments described. All posts except the double-diffusion treated posts were placed in a fence row. (See Figure 1.) The double-diffusion treated posts were placed in a square plot. Posts were evaluated annually in the spring to determine if rot was present and if posts were still serviceable. For determining the presence of decay a 1/4-inch

3 diameter steel rod was pushed into each post just below ground level by hand. If penetration was 1/8-inch or greater, some decay was assumed to be present. If each penetration was 1/8-inch or less, the post was counted as sound. Each post was subjected to a pound pull applied near the top of the post. Posts that broke under this pull were counted as failed or out of service. Posts that did not break when pulled were counted as still in service. RESULTS: The percent of sound (no decay) posts and the percent of posts remaining in service during the 32-year test period, are shown in Figure 2. For all species except paper birch, double-diffusion resulted in the most sound posts after 32 years. All of the double-diffusion treated aspen, balsam poplar, and white spruce were sound at the end of the test period. Seven of the paper birch posts were still sound at the end of the test period while four had failed and one had decay present, but was still in service. The pentachlorophenol cold soak treatment also resulted in respectable longterm service. All posts except two aspen posts were still in service at the end of the test period. All species had posts with some decay present at the end of the test period, and aspen and balsam poplar had more than percent of the posts where some decay was present. The capillary pull treatment using copperized chromated zinc chloride on trees harvested in the spring produced service lives nearly as high as the pentachlorophenol and double-diffusion treated posts. However, nearly all of these posts were partially decayed at the end of the study even though they were still in service. All of the other treatments, including the controls had much higher rates of decay and failure and are not recommended. DISCUSSION: For aspen, balsam poplar, and white spruce, double-diffusion produced the greatest proportion of sound posts. The pentachlorophenol cold soak treatment resulted in a greater proportion of sound birch posts than the double diffusion treatment. Pentachlorophenol treatment produced service lives comparable to double-diffusion treated posts for all species. However, except for birch, all of the double diffusion treated posts were sound at the end of the study while more than half of the pentachlorophenol treated posts were decaying. The capillary pull treatment used on spring-harvested material compared favorably with the above two treatments in terms of service life but the posts showed more decay. Based on the research described above, we recommend that either the doublediffusion or the pentachlorophenol methods as suitable for treating fence posts in Alaska. The capillary pull method could be used but it is not as good as the other two methods. (Note: Based on more recent research, the U.S. Forest Service Forest Products Laboratory suggests that when using the double diffusion method, sodium fluoride be used as the first chemical instead of sodium chromate. It also should be noted that since 1986 pentachlorophenol along with creosote and the inorganic arsenicals has been classified as a restricted use pesticide. This means that it can only be purchased by certified applicators and used under a certified applicator's direct supervision.)

4 TABLE 1. Treatment type, chemicals used, and description of treatment. Treatment No. Type Chemicals used Description of treatment Cold soak Capillary pull Same Brash on Soil treatment Double-diffusion Control Control Pentachlorophenol Copperized chromated zinc chloride Same Creosote Copper sulfate Copper sulfate and sodium chromate None None Posts were peeled and air dried six months prior to submersing in 5% penta 95% fuel oil solution until absorbing five pounds/cubic foot. Butts of green unpeeled posts from trees cut in the autumn were placed in the 11 percent solution until a gallon of solution was taken up per cubic foot of wood. Butts of green unpeeled posts from trees cut in the spring were placed in the 11 percent solution until a gallon of solution was taken up per cubic foot of wood. Posts were peeled and air dried six months before a single heavy coat of creosote was brushed on. Posts were peeled and air-dried prior to installation with one-half pound of CuS4 in the top four inches of soil around the post. Posts were peeled and treated while green. Posts were submersed three days in the eight percent CuS4 solution, then submersed three days in the eleven percent Na2CrO4 solution. Posts were unpeeled and were installed while green. Posts were peeled and were installed while green. FIGURE 1 Fence Row of Treated Posts at the Agriculture and Forestry Experiment Station Palmer, Alaska

5 UJ CL FIGURE 2 THE PERCENT OF SOUND (NO DECAY) POSTS AND THE PERCENT OF POSTS REMAINING IN SERVICE DURING THE 32-YEAR TEST PERIOD ASPEN BALSAM POPLAR PAPER BIRCH WHITE SPRUCE Pentachlorophenol Cold Soak \ "o Copperized Chromated Zinc Chloride (Fall) \ Copperized Chromated Zinc Chloride (Spring) 32 o Creosote (Brush on) YEARS InService NoDecay

6 PERCENT FIGURE 2 THE PERCENT OF SOUND (NO DECAY) POSTS AN! AND THE PERCENT OF POSTS REMAINING IN SERVICE DURING THE 32-YEAR TEST PERIOD «wrtiti ^s~n BALSAM POPLAR PAPER BIRCH WHITE SPRUCE t-x \ 8 U o CuSO4 ir, i~> \5 v\ : isoil > \ 3 Id 24 3 "S. p \v ^-^ V * v. <, "< Double Diffusion ( l\ " Control [Un pooled) } ' CuS4&NaCrO4). V v\ \ V, '- U \ \ v\ \. K ' Q 3 ]$ Control (Pooled) VJPAPh** In 5WvirA No Deem/