Technical Note: Effect of Soil on the pH of Treated Wood in Ground Contact

The pH of treated wood in ground contact will influence the type and activity of decay and nondecay microorganisms present as well as the solubility and leaching of metallic biocides. To determine the soil effect on the pH of treated wood in ground contact, southern pine sapwood samples commercially treated with five copper-based preservatives along with untreated pine were placed in pots filled with five different soils. The pH of the wood samples after a 12-wk exposure to basic soils increased, as anticipated. However, the pH of wood in acidic soils was more complex than expected with the treated wood pH always greater than soil pH. Two possible chemical mechanisms to explain the nonintuitive results for treated wood in acidic soils are given

Synergistic Wood Preservatives: Terrestrial Microcosms (TMCs) and Field Exposure Efficacy Studies of the Synergistic Copper: Pyrithione Mixture

On the basis of short-term laboratory tests using various wood decay fungi, we previously found that the mixture of copper (II) and sodium pyrithione is highly synergistic. In this study we examined the efficacy of this mixture in protecting wood using terrestrial microcosms (TMCs) with three different Swedish soils, and field stake (ground contact) tests in two different locations in Mississippi. After 12 months of exposure in TMCs, the copper: pyrithione mixture was found to be more effective than either component alone, with only slight degradation due to tunneling bacteria in a compost soil TMC. The field stake test, after 6 years of exposure, showed that a mixture of 0.31 pcf or greater copper (as CuO) and 0.063 pcf or greater pyrithione (as the sodium salt) was approximately as effective as about 0.35 pcf CCA in preventing fungal and termite degradation

Technical Note: The Susceptibility of Chemically Treated Southern Hardwoods to Subterranean Termite Attack

Ongoing research into chemically treating southern hardwoods for producing structural composite lumber suggests that some improvements may be imparted by modifying the wood. How chemical treatment(s) affect modified wood durability, particularly resistance to Reticulitermes flavipes, was the objective of this study. Water-saturated samples of yellow-poplar, sweetgum, and red oak were heated at 150°C for 30 min in two solutions: water and 1.0% NaOH; controls were also included. Samples were subjected to the AWPA E1-09 no-choice termite test in which mass loss from R. flavipes was determined. The species and treatments independently and significantly affected the mass loss. Yellow-poplar, which had the lowest specific gravity, averaged significantly greater mass loss than sweetgum and red oak for all three exposures. All species treated in water or NaOH showed a higher degree of termite degradation as compared with the controls

Technical Note: The Susceptibility of Chemically Treated Southern Hardwoods to Subterranean Termite Attack

Ongoing research into chemically treating southern hardwoods for producing structural composite lumber suggests that some improvements may be imparted by modifying the wood. How chemical treatment(s) affect modified wood durability, particularly resistance to Reticulitermes flavipes, was the objective of this study. Water-saturated samples of yellow-poplar, sweetgum, and red oak were heated at 150°C for 30 min in two solutions: water and 1.0% NaOH; controls were also included. Samples were subjected to the AWPA E1-09 no-choice termite test in which mass loss from R. flavipes was determined. The species and treatments independently and significantly affected the mass loss. Yellow-poplar, which had the lowest specific gravity, averaged significantly greater mass loss than sweetgum and red oak for all three exposures. All species treated in water or NaOH showed a higher degree of termite degradation as compared with the controls

Review of Laboratory and Outdoor Exposure Efficacy Results of Organic Biocide: Antioxidant Combinations, An Initial Economic Analysis and Discussion of a Proposed Mechanism

As previously reported, the combination of various organic biocides with relatively high levels of commercial antioxidants always increased the biocides' efficacies against wood-destroying fungi in short-term laboratory decay tests. The two principal antioxidants examined, propyl gallate (PG) and butylated hydroxytoluene (BHT), are low cost and benign. In reviewing ground-contact outdoor exposure results, samples treated with the biocide chlorothalonil and the antioxidant BHT had 2-3-fold enhanced efficacy after four years of exposure against decay and termite degradation compared to stakes treated with only the biocide. In above-ground outdoor exposure tests after three years of exposure, lap-joint samples treated with only BHT at the relatively low retention of 0.94 kgm-3 had significantly less fungal decay than untreated samples. In addition, mini lap-joint samples treated with a quaternary formulation and 2.56 kgm-3 BHT and exposed in Hilo, HI, for two years, had more than 3-fold greater decay resistance than samples without BHT. However, relatively poor results were observed for both ground-contact and above-ground samples treated with various biocides and the antioxidant PG. Less BHT may be required to protect wood outdoors than the initial laboratory decay tests indicated. The antioxidant concept appears to be an economical option for totally organic systems. A mechanism by which BHT protects wood against fungal degradation is proposed