Stake Tests of Northeastern Species Treated with Copper-based Preservatives

Book excerpt: The value of some northeastern tree species could be increased if they could be adequately treated with preservatives and shown to be durable in outdoor exposures. This paper reports on research to evaluate the ground-contact durability of northeastern species treated with copper-based preservatives. Stakes (19 by 19 by 457 mm) cut from balsam fir, eastern hemlock, eastern spruce, white pine, or red maple were treated with one of four concentrations of chromated copper arsenate, copper citrate, alkaline copper quat, or copper azole and placed into the ground at a test site in southern Mississippi. Similarly treated Southern Pine stakes were included for comparison. For 5 years, the stakes were rated annually for decay and termite attack. Untreated stakes of all wood species failed rapidly, indicating that none of the species evaluated have significant natural durability. Occasional failures have occurred in treated stakes, typically at the lower preservative retentions. Treated Southern Pine and eastern hemlock stakes have experienced the fewest failures, with treated white pine stakes performing nearly as well. Treated eastern spruce and red maple stakes had the most failures, and treated balsam fir stakes also had substantial failures. The failures in eastern spruce and balsam fir stakes appear to be attributable to poor preservative penetration and retention within individual stakes. Failures in the red maple stakes may be attributable to the differences in hardwood anatomy and the distribution of preservative within the wood structure. Of the northeastern species evaluated, eastern hemlock and white pine appear to perform most similarly to Southern Pine when treated with the copper-based preservatives. However, further exposure time is needed to allow more definitive conclusions.