Limited long-term field data exist evaluating the benefit of chemical wood preservatives on refractory wood species with abundant heartwood. The objective of this study was to determine the effectiveness of preservative-treated refractory solid heartwood comprised of southern pine, Douglas-fir, or Engelmann spruce. Non-incised and incised solid lumber of these species were treated to three different retentions of either chromated copper arsenate (CCA) or ammoniacal copper arsenate (ACA) and placed in ground contact (AWPA E7) at a Mississippi field test site in 1975. Field stakes were rated for decay and insect damage every two to five years. The 40-year rating data showed that incising improved long term performance of southern pine and Engelmann spruce samples treated to lower retentions with either CCA or ACA, although CCA treated material outperformed ACA. Incising had little to no effect on preservative uptake or performance of Douglas-fir heartwood treated with either preservative.
Mankowski, Mark E.; Lebow, Stan; Kirker, Grant; Gjovik, Lee. 2017. Long term durability of solid heartwood stakes treated with ACA or CCA. In: Proceedings, one hundred thirteenth annual meeting of the American wood protection association. Las Vegas, NV: April 9-11. 13 p.