Potential for the use of hydroxylamine derivatives as wood preservatives

Conventional wood preservatives have provided excellent protection against wood-degrading organisms; however, increasing public mistrust of these chemicals has encouraged a search for alternative wood protection strategies that take advantage of the physiological capabilities of the target organisms. One approach is to use chelators to sequester elements required by fungi to initiate the decay process. Oxalic acid is produced by nearly all brown-rot fungi and its presence is believed to be necessary for the initiation of decay. Competitive compounds can negate the role of oxalic acid, thereby limiting decay initiation (Viikari and Ritschkoff 1992). Green et al. (1997) reported that the chelator N,N-naphthaloylhydroxylamine sharply reduced both fungal decay and termite attack of southern pine (Pinus spp.) sapwood. This report describes laboratory trials of 17 other hydroxylamine derivativesagainstwhite-andbrown-rot fungi. Materials and methods The efficacy of the compounds was examined by using a scaled-down version of the soil block test (AWPA 1999) developed by Scheffer et al. (1987). Ponderosa pine sapwood (Pinus ponderosa Laws.) samples (10 by 10 by 5 mm long) were ovendried (104°C) and weighed (nearest 0.001 g), then treated with solutions of 0.5, 1.0, or 2.0 percent of 1 of 17 compounds (Table 1) using a double vacuum process (20 min. @ 800 kPa vacuum, drop solution, release vacuum, apply 20 min. vacuum, and release). The blocks were then blotted dry and reweighed to determine net solution uptake, then covered with moist paper and left for 24 hours at room temperature (21° to 23°C) to allow any wood/ chemical reactions to proceed. The blocks were ovendried (104°C) and weighed. Each treatment was replicated on 12 blocks. The blocks were then placed into sealable plastic bags and sterilized by exposure to 2.5 mrads of ionizing radiation from a cobalt 60 source. Decay chambers were 30-mL glass bottles, which were half filled with a moist garden loam. A 10by 10by 2-mm-long thick strip of red alder (Alnus rubra Bong.) for the white-rot fungus or western hemlock (Tsuga heterophylla (Raf.) Sarg.) for the brown-rot fungus was placed on the surface, then the jars were loosely capped and autoclaved for 45 minutes at 121°C. After cooling overnight, the jars were autoclaved for 15 minutes at 121°C to kill any spore-forming bacteria. The decay chambers were inoculated with agar discs cut from cultures of either the white-rot fungus Trametes versicolor (L. ex. Fr.) Pilat (Isolate Madison R105) or the brown-rot fungus Gloeophyllum trabeum (Pers. ex. Fr.) Murr. (Isolate Madison 617). The bottles were then capped and incubated un-