Abstract:
Antisapstain compositions capable of protecting freshly sawn timber for periods of three months or more in warm, moist environments have been developed. Studies centred on active ingredients which have suitable health, safety and environmental properties for the timber industry, and present no particular regulatory difficulties. Limitations of antisapstain field trials are discussed, and improvements related to substrate presentation, control of treated timber moisture and ambient conditions, and evaluations of infected timber levels, have been incorporated into method development. Attempts to improve chlorothalonil efficacy by preparation of solubilised chlorothalonil products met with limited success because no suitably low cost, low odour solvents could be found. Formulations based on cuprous thiocyanate, solubilised cuprous ions, or zinc compounds generally had poor efficacy compared to oxine copper products, which are currently favoured by the industry. A major outcome of the research was the development of oxine copper products based on solubilisation by methane sulphonic acid (MSA). The products are chemical stable, have good fungicidal efficacy, and impart minimal colour to the wood. Carbendazim is a compatible and efficacious co-active in these formulations but health and safety concerns associated with carbendazim led to investigation of alternative co-actives. The quaternary ammonium salt, DDAC, was a particularly efficacious co-active for control of sapstain and decay fungi, although a general weakness against Trichoderma mould was noted. Introduction of DDAC to oxine copper formulations resulted in a considerable reduction of corrosiveness of antisapstain working solutions. Corrosion testing, developed in this study, showed that a number of heterocyclic compounds had corrosion inhibitive properties but the greatest effects were obtained with triazole compounds, such as propiconazole and tebuconazole, which are also known fungicides. The developed oxine copper products, based on MSA solubilisation and containing DDAC and triazoles, may have commercial application.