Skip to Main Content
Due to a lapse in federal funding, this USDA website will not be actively updated. Once funding has been reestablished, online operations will continue.
Mechanisms of protection by NHA against fungal decayAuthor(s): Frederick Green; William Henry; Tor Schultz
Source: Thirty-third Annual Meeting of the International Research Group on Wood Preservation, 2002 May 12-17, Cardiff, South Wales, UK. Stockholm, Sweden : IRG Secretariat, 2002:  pages
Publication Series: Miscellaneous Publication
PDF: View PDF (176 KB)
DescriptionTreating wood with the water-borne sodium salt of N'-N-naphthaloylhydroxylamine (Na-NHA) protects wood against decay and termite damage. Initial testing indicated little or no inhibition of sapstain fungi, molds, or soft-rot fungi by Na-NHA, suggesting that the mechanism by which this compound protected wood was complex and not that of a broad-spectrum biocide. Previously, we (Green et al, 1997) suggested that the protective mechanism was due to Na-NHA complexing with calcium ions to disrupt fungal metabolism, and/or binding of Na-NHA to the calcium in pit membranes, which acts as a physical barrier to fungal colonization. More recent experiments suggest an alternate mechanism. Specifically, pKa measurements of Na-NHA show that the sodium salt will be essentially fully protonated when impregnated into SYP which is naturally acidic (pH at or below 5.5). Furthermore, the protonated form (H-NHA) was more fungicidal than Na-NHA against two white- and two brown-rot fungi, with the bioactivity approaching that of several commercial organic fungicides. The moderate fungicidal activity of H-NHA is not surprising; the compound is a polyaromatic hydrocarbon much like many of the compounds in creosote. By precipitating mainly at the pit membranes, H-NHA or Ca-NHA serves as a fungicidal barrier to inhibit fungal hyphae from spreading to adjacent cells through the pits. Studies of H-NHA combined with three commercial organic biocides showed that only one combination was synergistic, which further suggests that NHA protects wood by a biocidal mechanism rather than being simply a compound is extremely water insoluble and will thus not leach from wood in outdoor exposure. NHA may also have metal chelating and/or antioxidant properties which further assists in protecting wood. non-biocidal additive.
- We recommend that you also print this page and attach it to the printout of the article, to retain the full citation information.
- This article was written and prepared by U.S. Government employees on official time, and is therefore in the public domain.
CitationGreen, Frederick; Henry, William; Schultz, Tor. 2002. Mechanisms of protection by NHA against fungal decay. Thirty-third Annual Meeting of the International Research Group on Wood Preservation, 2002 May 12-17, Cardiff, South Wales, UK. Stockholm, Sweden : IRG Secretariat, 2002:  pages
KeywordsNHA, wood-decaying fungi, fungal decay, wood preservatives
- Production of polygalacturonase and increase of longitudinal gas permeability in southern pine by brown-rot and white-rot fungi
- Multicomponent biocide systems protect wood from decay fungi, mold fungi, and termites for interior applications
- Inhibition of decay fungi using cotton cellulose hydrolysis as a model for wood decay
XML: View XML