Graduate Thesis Or Dissertation
 

Phytosanitation of Douglas-fir (Pseudotsuga menziesii) logs to mitigate the risk of artificially disseminating Phytophthora ramorum within the global trade of timber

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/dv13zx70r

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  • Phytophthora ramorum is a plant pathogen that was accidentally introduced to the United States. This invasive microorganism has killed over a million trees in California and Oregon, and continues to spread to new areas. Diseased areas have been nationally quarantined to prevent further spread and more than ninety countries include the organism on regulated pest lists or mention it in their legislation. Legislation and quarantines can slow the spread, but it will also be important to develop methods for eliminating the presence of this organism on various plant materials. Among the most important would be woody tissues, notably logs exported from infested areas. This study examined the potential for P. ramorum to colonize Douglas-fir logs and the ability of disodium octaborate tetrahydrate (DOT), a water diffusible fungicide, to control P. ramorum in Douglas-fir logs. Phytophthora ramorum was capable of growing into Douglas-fir sapwood but the results were inconsistent. DOT levels above 0.1% Boric Acid Equivalent (BAE) were inhibitory to P. ramorum in a boron amended media bioassay, while levels above 1.5% BAE were lethal, indicating that boron has the potential to be an effective mitigation measure. Boron was capable of diffusing through bark and into the sapwood of the Douglas-fir log sections and diffusion was improved slightly through inclusion of glycol. While further research is needed to confirm that P. ramorum can grow into Douglas-fir sapwood, the results indicate that boron diffusion might be a useful method for mitigating the risk of spreading this pathogen on logs.
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