Over 50 years ago, the USDA-Forest Products Lab established tests in a high decay
and high termite hazard zone in southern Mississippi. During the last five decades, periodic reports have
been issued by researchers located at the USDA-FPL, in Madison, WI, on the efficacy and performance of
southern pine fence posts treated with a variety of wood preservatives.
The objective of the original study was to evaluate the efficacy and performance of over 100
wood preservatives and wood preservative systems in southern pine posts in a severe hazard site. The test
site, in southern Mississippi in AWPA Hazard Zone 5 contains severe decay potential and severe termite
exposure.
Tenino Copper Naphthenate (2% copper as metal) meets the American Wood Protection Association’s (AWPA) M4 STANDARD FOR THE CARE OF PRESERVATIVE-TREATED WOOD PRODUCTS as defined in Section 7.1.1 for field treating abrasions, cuts and holes in treated lumber, timbers, and decking.
Copper Naphthenate has been used as a wood preservative for over one hundred years with many applications for use including; fence posts, canvas, nets, greenhouses, utility poles, and wooden structures in ground contact. Tenino provides protection against wood decay and the superior water repellent qualities of an oil borne wood preservative.
Copper naphthenate is approved for use by the American Wood Preservers Association (AWPA) for treatment of many wood products including lumber, poles and posts. Call the AWPA for a copy of the full standard. (817) 326-6300.
The Copper Care family of wood preservatives includes copper naphthenate based products that have a proven record of safe and effective performance as a fungicide/insecticide for protection against rot mildew and moisture on exterior wood surfaces.
This paper reviews the efficacy and field trials of copper naphthenate in various wood
species. Included in this discussion are chemical and physical characteristics of copper
naphthenate preservative systems, the effect on wood treated with copper naphthenate
or copper naphthenate wood preservative systems, and a review of the long-term
efficacy trials, in various species of wooden fence posts. Included in this discussion are
independent results from the USDA- Forest Products Lab testing in Harrison
Experimental Forest near Gulfport, MS, results from the Tennessee Valley Authority on
Fence Post Tests in Tennessee, summary of Test results from fence post tests in
Canada and a brief mention of ongoing tests in Auburn, AL and Corvallis, OR. Included
in this discussion is the typical plant handling characteristics of copper naphthenate and
its diluted solutions. Based on all the data, copper naphthenate is an excellent
preservative choice for both pressure and non-pressure treatment of wooden posts of
all species.
In this study the performance of copper naphthenate (Cu-Nap) and pentachlorophenol (Penta)
treated pine stakes against decay and termite attack were compared at two test sites in
Mississippi. Four different petroleum oils meeting AWPA Standard P9-A were used as carriers
for these wood preservatives. After ten years exposure, the efficacy of Cu-Nap at a retention
level of 0.05 pcf Cu was equivalent or slightly better than Penta at a retention level of 0.40 pcf.
Copper naphthenate has been used for over 50 years in the United States in various wood treating
applications. Copper naphthenate is a copper carboxylate made with naphthenic acid, which occurs
naturally in petroleum. Copper naphthenate is an EPA registered general use wood and fabric preservative that can be used with a high degree of safety. It is not considered a hazardous waste, it is non-corrosive, non-conductive, non-blooming, and it has low mammalian (e.g. human) toxicity.
Based on the information reviewed, it appears that copper naphthenate is one of the safer and more
environmentally acceptable pesticide products in the marketplace today. No consequential short or long term
health effects are expected to occur from properly treated copper naphthenate wood in accordance
with EPA labeled directions.