A screening test was carried out using ethanedinitrile (EDN) as a candidate fumigant to replace methyl bromide for efficacy against a selection of forest pests, including the pinewood nematodes ( Bursaphelenchus xylophilus ) and four tree pathogens: Heterobasidion annosum , Geosmithia morbida , Phytophthora ramorum and Ceratocystis fagacearum . Two EDN concentrations were tested: 50 and 100 g/m 3 at two different temperatures and six exposure times. In our tests, EDN was very efficient in killing pathogens in all test parameter combinations, including short exposure times and lower concentration, apart from C . fagacearum surviving short 1 h exposure and G . morbida surviving after 1 and 3 h of exposure. Pinewood nematodes in the small wood blocks were effectively killed at all test parameter combinations. In log sections where deeper nematode infestations were present, nematode survivors at 50 and 100 g/m 3 after 1, 3, and 6 h exposure were observed. This suggests that the fumigant was not efficacious at lower exposure times, while penetrating log sections. Both 50 and 100 g/m 3 dosages were effective after 24 h exposure, indicating that longer retention times are required to effectively kill pine wood nematodes in deeper wood sections. The lower temperature did not affect the efficacy of EDN. This indicates that EDN could successfully eradicate pinewood nematodes in logs over 24 h of exposure, or even less exposure time, at targeted concentrations.

Invasive exotic pathogens pose a threat to trees and forest ecosystems worldwide, hampering the provision of essential ecosystem services such as carbon sequestration and water purification. Hybridization is a major evolutionary force that can drive the emergence of pathogens. Phytophthora ramorum , an emergent pathogen that causes the sudden oak and larch death, spreads as reproductively isolated divergent clonal lineages. We use a genomic biosurveillance approach by sequencing genomes of P. ramorum from survey and inspection samples and report the discovery of variants of P. ramorum that are the result of hybridization via sexual recombination between North American and European lineages. We show that these hybrids are viable, can infect a host and produce spores for long-term survival and propagation. Genome sequencing revealed genotypic combinations at 54,515 single nucleotide polymorphism loci not present in parental lineages. More than 6,000 of those genotypes are predicted to have a functional impact in genes associated with host infection, including effectors, carbohydrate-active enzymes and proteases. We also observed post-meiotic mitotic recombination that could generate additional genotypic and phenotypic variation and contribute to homoploid hybrid speciation. Our study highlights the importance of plant pathogen biosurveillance to detect variants, including hybrids, and inform management and control.

Wood is vulnerable to significant color changes when used in exterior applications. Some copper-based wood preservatives use colorants to minimize this color change. This paper examines the ability of a peroxide post-treatment to turn wood impregnated with micronized basic copper carbonate (CuCO3·Cu(OH)2) (MBCC) a stable brown color. MBCC-treated wood, with and without peroxide post-treatment, along with associated controls were evaluated for color change, erosion and black-stain fungal resistance after exposure to artificial photo-degradation. The impact of the peroxide treatment on copper leaching was assessed in a laboratory experiment, and the impact on copper reactivity was assessed by electron parametric resonance (EPR) spectroscopy. Peroxide post-treatment of wood pressure impregnated with MBCC was shown to reduce color change by more than 50% compared to controls. Erosion due to photo-degradation and colonization by black-stain fungi were lower in samples treated with MBCC than in untreated controls and were relatively unaffected by peroxide post-treatment. The peroxide post-treatment was associated with increased amounts of mobile copper. This led to increased susceptibility to leaching and to a more than 60% increase in the amount of copper than had reacted with the wood.

Alternative and higher value uses are needed for residual materials generated from wood products processing. Western redcedar sawdust contains an array of unique chemicals and has the potential to be used to alter the appearance, stability and durability of non-durable timbers. Here it was hypothesized that impregnation of Western redcedar heartwood extractives into Pacific silver fir would decrease shrinkage, hygroscopicity, and susceptibility to decay. Western redcedar hot water extracts were obtained from sawdust and used to pressure-treat Pacific silver fir blocks. Extractive impregnation enhanced the wood’s appearance and gave it a more cedar-like brown colour. Impregnated samples had reduced shrinkage, but were not as dimensionally stable as Western redcedar heartwood. Pacific silver fir blocks impregnated with water-soluble extractives were also highly susceptible to leaching, and leached samples had similar shrinkage values to untreated controls. In contrast, leaching had little effect on the hygroscopicity of the Western redcedar heartwood. Extractive-impregnated Pacific silver fir blocks had increased resistance to decay by two brown-rot fungi, and showed resistance similar to that of Western redcedar heartwood. However, leached blocks did not have the same decay resistance.

Understanding the relationship between extractives and decay resistance in western red cedar (WRC) is essential for breeding durable planting stock. To date, most such work has focused on resistance to mycelial attack. However, this is potentially misleading since WRC is largely used in above-ground applications where basidiospore germination is the primary way in which the wood is initially colonized. Efficacy against basidiospores is likely a critical factor affecting wood’s decay resistance in above-ground applications. In this study the effect of selected extractives on basidiospore germination was evaluated. Partially-extracted WRC veneer samples, and spruce samples treated with beta-thujaplicin, thujic acid, or plicatic acid were used. Beta-thujaplicin and thujic acid were associated with significantly reduced rates of Gloeophyllum sepiarium, Fomitopsis palustris, and Dichomitus squalens basidiospore germination. Plicatic acid was not associated with any effect on basidiospore germination. Planting stock that generates heartwood with high concentrations of thujaplicins and thujic acid should be selected to yield wood that will be resistant to basidiospore germination.