Worldwide forest health continues to be at risk and subject to dangerous forest pests, as trade in many types of commodities, potentially carrying pests, increases in terms of volume, trading partners and destinations. Although trading countries make their best efforts to prevent pest movement and transfers through pest management, legislative actions and regulations, such as those managed by the International Plant Protection Convention (IPPC), are required. IPPC develops International Standards for Phytosanitary Measures (ISPMs) as guidance documents for trading countries, upon which they build their own national pest management strategies to meet their obligations under the treaty. Some standards are commodity-based and prescriptive regarding how a risky commodity is to be treated and managed, in order to significantly reduce pest risk. A good example is ISPM 15, which sets the standards of management and treatment for wood packaging (IPCC Secretariat, 2019a). Other commoditybased standards include ISPM 36 (Integrated measures for plants for planting), ISPM 38 (International movement of seeds) and ISPM 39 (International movement of wood) (IPCC Secretariat, 2017, 2019b, 2021. All offer guidance for trading countries about the risks associated with the commodity, as well as potential management strategies to prevent pest transfers. ISPM 28 describes the requirements for submission and evaluation of the efficacy data of new treatments for specific pests and commodities and contains annexes of evaluated and adopted phytosanitary treatments for control of regulated
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.
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.
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