Progress 12/16/07 to 12/31/10
Outputs
OUTPUTS: Three Pacific Northwest bare-root conifer nurseries were selected for the fumigation study: The Webster Nursery in Thurston county, near Olympia, Washington, the Aurora Nursery in Marion county, near Aurora, Oregon and the IFA Nursery in Clackamas county, near Canby, Oregon. A representative production nursery block in each facility was chosen for the fumigation trial in July 2008. At each nursery a randomized complete block study design was set up with six treatments and four replicates of each treatment. All fumigation was conducted at all three facilities by Trident Fumigation Inc. between August 4-8, 2008. Each nursery constituted a separate experiment. Prior to fumigation, each field had its soil leveled. Soil physical and chemical properties were determined in four locations from each field one-three days prior to fumigation. Nutrient analysis samples, pH, cation exchange capacity, percent organic matter, and percent base saturation were analyzed. Soil bulk density was determined at four locations from each field. Soil moisture was determined from soil samples taken immediately prior to fumigation at each facility. Soil and air temperature were recorded at each nursery. We sampled for Fusarium in soil and roots. Sampling of soil Fusarium populations was initiated in May 2008 in each nursery block to determine the Fusarium distribution prior to laying out treatment plots. Soil samples were assayed for Fusarium. A composite of soil cores was taken in each treatment plot to determine soil Fusarium population abundance. Soil sampling occurred one-three days before fumigation, two weeks after fumigation and seven months after fumigation. Discarded (cull) seedlings were collected from outdoor piles at each nursery during May 2008. Cull seedling roots were washed free of soil, cut into segments, sanitized and rinsed. Fusarium isolates from these sources were grown and added to the general culture population from each facility to be used in the buried inoculum trial. Six Fusarium culture isolates were selected using morphological characteristics from each of three nurseries. Three isolates from each nursery were isolated from soil cultures from the preliminary study and three isolates from each nursery were isolated from root cultures, taken from seedlings found in the nursery's cull pile. We extracted DNA for Fusarium, and then performed polymerase chain reaction (PCR) amplification. We prepared agarose gels, which then underwent electrophoresis. We examined the gels using an UV illuminator and photographed them. We used a spectrophotometer to determine the amount of resulting PCR product DNA. PCR product was sent to the University of Washington Department of Biochemistry DNA Sequencing Facility, where reactions and sequence analyses were performed. We performed statistical analyses on the results. PARTICIPANTS: Anna Leon, Masters student, University of Washington College of Forest Resources. Robert Edmonds, Professor, University of Washington College of Forest Resources. Dean Glawe, Professor, University of Washington College of Forest Resources. Darlene Zabowski, Professor, University of Washington College of Forest Resources. Willis Littke, Affiliate Assistant Professor, University of Washington College of Forest Resources. TARGET AUDIENCES: Target audiences include Washington State governmental agencies and non-governmental organizations, nursery managers, foresters, researchers, educators, students, and the general public. PROJECT MODIFICATIONS: There were problems acquiring virtually impermeable film (VIF) tarp within the time frame of the study, that was the correct size for fumigation equipment and that had UV protection to prevent the tarp from breaking down. Tarp breakdown was a significant issue in this study with approximately 40% of the VIF tarp broken 15 days after injection. Although this occurred well after the prescribed 5-7 days post-application, it somewhat negated the purpose of a less permeable tarp. As more studies successfully use VIF tarp applications, it is likely the mechanical problems and physical deterioration that the fumigation companies currently have using VIF tarp in the Pacific Northwest will be resolved.
Impacts
As methyl bromide fumigation faces restriction from use in Douglas-fir nurseries, metam sodium and methyl iodide were shown to be promising alternatives for use against Fusarium. Soil properties appeared to have little effect on fumigation and Fusarium populations, with the exception of bulk density. There was no difference in fumigant efficacy with depth at the Canby and Aurora nurseries. However, Fusarium populations were much higher at 30 cm than 15 cm at the Webster nursery. This was likely due to high soil bulk density at 30 cm at the Webster nursery. Metam sodium and methyl iodide were both effective fumigants at 15 cm and 30 cm against Fusarium, however dimethyl disulfide proved to be less effective. Virtually Impermeable Film (VIF) tarps were equally or more effective than the traditional high-density polyethylene (HDPE) tarps. Both Fusarium oxysporum and Fusarium commune were found in all three of the Douglas-fir nurseries examined in this study. This expands upon the work done by Skovgaard et. al. (2003) and Stewart et. al. (2006) by showing that F. commune can be found in Pacific Northwest Douglas-fir nurseries on the western side of the Cascade Mountains along with Fusarium oxysporum. However, with the rather small amount of genetic data in this study, it was not possible to confidently conclude which species were recovered from each fumigation treatment.
Publications
- Leon, A.L. 2009. Chemical Alternatives to Methyl Bromide for Control of Fusarium oxysporum and Fusarium commune in Douglas-fir Nurseries in the Pacific Northwest. Master of Science thesis, University of Washington College of Forest Resources.
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Progress 10/01/07 to 10/01/08
Outputs
OUTPUTS: This project is determining alternatives to methyl bromide for reducing forest nursery pathogens in the production of Douglas-fir seedlings in the Pacific Northwest. Alternative treatments are being tested at two nurseries in Washington and one nursery in Oregon. This is a cooperative project between Weyerhaeuser, the Washington DNR and the Oregon State University Nursery Cooperative. Levels of soil fungal pathogens are being assessed before and after treatment. PARTICIPANTS: Anna Leon, University of Washington graduate student Robert Edmonds, Professor, University of Washington Willis Littke, Research Scientist, Weyerhaeuser Company. TARGET AUDIENCES: Nursery managers, plant pathologists PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
International goals are to discontinue ozone depleting chemicals, such as the soil fumigant methyl bromide. The data from the project will be important in determining if a suitable substitute can be found that will still enable production of healthy seedlings for the forest industry.
Publications
- No publications reported this period
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