Evaluation of the termite resistance of wood pressure treated with copper naphthenate
1993
Grace, J.K. | Yamamoto, R.T. | Laks, P.E.
Southern pine wafers pressure-treated with copper naphthenate in American Wood-Preservers' Association P9 Type A oil or in toluene were evaluated for resistance to attack by the Formosan subterranean termite Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae). Wood samples were pressure treated to target copper retentions of 0.040, 0.075, 0.095, or 0.150 pcf, conditioned to simulate field exposure, and exposed to termites in 4-week no-choice and two-choice laboratory tests. Copper retentions were assayed by X-ray fluorescence after treatment, after leaching, and again after exposure to the termites. An approximate 20 percent loss of copper after weathering and termite exposure was noted in samples treated to target retentions of 0.095 and 0.150 pcf Cu. With or without a heavy oil carrier, copper naphthenate showed some toxicity to termites and deterred termites from feeding on the treated wood. At the highest target retentions of 0.095 and 0.150 pcf Cu, southern pine weight losses from termite feeding did not exceed 4 percent in no-choice tests nor 1 percent in two-choice tests. Similar results were observed in no-choice tests with Douglas-fir blocks treated with copper naphthenate in oil or toluene. Field data are needed, but these results indicate that copper naphthenate pressure treatments are of value in protecting wood from attack by the Formosan subterranean termite.
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