Efficacy of alternatives to zinc naphthenate for dip treatment of wood packaging materials

• Several alternative preservatives improved protection under all test conditions.
• Most alternative preservatives were more effective against white-rot fungi.
• Fungal copper tolerance was greater than that typically observed for pressure treatments.
• Some alternatives were less effective in protecting yellow poplar from termite attack.

Research is being conducted to evaluate potential preservatives to replace zinc naphthenate (ZnN) for use in dip-treatment of wooden packaging materials. In this study, laboratory tests evaluated the efficacy of preservatives in protecting Southern pine and yellow poplar against decay fungi and termites. Nine preservatives were evaluated at one or two concentrations, and in some cases with two dip times. The results of this study indicate that higher concentrations of most of the preservatives evaluated will provide protection similar to or greater than that of ZnN. Four of the formulations provided protection equivalent to or greater than that of ZnN across all of the test organisms. Lower concentrations of some of the copper-based preservatives were less effective than ZnN in preventing colonization of Southern pine by the copper tolerant fungus Postia placenta, but most formulations were more effective than ZnN in protecting yellow poplar against white-rot fungi. The test formulations tended to be more effective than ZnN in preventing termite feeding on southern pine, but some were less effective than ZnN in protecting yellow poplar from termites. Efficacy was found to increase with preservative concentration in several cases, but did not increase with a longer dip time.