Thesis
Evaluation of seed and drench treatments for management of damping-off and seedling blight pathogens of spinach for organic production
Washington State University
Master of Science (MS), Washington State University
2007
Handle:
https://hdl.handle.net/2376/102704
Abstract
There are many concerns regarding losses to seedborne and soilborne pathogens in organic production systems because of limited effective options available for disease management that satisfy organic standards. Seed treatments can be inexpensive and effective, including those with biological control agents (BCAs). However, the reliability of BCAs for disease control is affected by crop species, whether a pathogen is seedborne or soilborne, and numerous abiotic factors. The efficacy of a range of seed and drench treatments for control of soilborne seedling blight and damping-off pathogens was investigated using spinach as a model small-seeded vegetable. The seed and drench treatments included those that were EPA registered and approved for use in organic agriculture as defined by the National Organic Standards, and those that were being developed for registration and compliance with organic standards. Greenhouse inoculation rate trials were completed for each of three soilborne pathogens, Fusarium oxysporum f. sp. spinaciae, Pythium ultimum, and Rhizoctonia solani. Results were then used to evaluate 14 seed and drench treatments in greenhouse trials against each pathogen. For P. ultimum, two experimental seed treatments, Experimental #1 and #2, provided equivalent control to that provided by a conventional fungicide seed treatment, Apron XL LS; while Natural II, Natural X, and Subtilex seed treatments each suppressed damping-off significantly in only one of two trials. For F. oxysporum f. sp. spinaciae, drenches with a compost tea or Prestop, and seed treatment with Yield Shield suppressed post-emergence wilt significantly in one of two trials; but no treatment was highly effective. For R. solani, Experimental #1 and Natural II seed treatments reduced damping-off as effectively as a drench with the conventional fungicide Terraclor. Seed health assays revealed that treatments with Experimental #1, Experimental #2, or Mycostop Mix significantly reduced the incidence of seedborne Verticillium and Alternaria. Natural II and Natural X seed treatments significantly reduced early germination in seed germination assays. Selected treatments were evaluated further under field conditions at three locations in western Washington. There was little consistency in results among field trials. However, Experimental #1 and #2 seed treatments consistently caused significantly earlier emergence than the other treatments. In contrast, the compost tea drench resulted in low total emergence and low spinach biomass, but also low post-emergence wilt in two of three trials.
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Details
- Title
- Evaluation of seed and drench treatments for management of damping-off and seedling blight pathogens of spinach for organic production
- Creators
- Jaime Anne Cummings
- Contributors
- Lindsey J. Du Toit (Degree Supervisor)
- Awarding Institution
- Washington State University
- Academic Unit
- Plant Pathology, Department of
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University; Pullman, Wash. :
- Identifiers
- 99900525100901842
- Language
- English
- Resource Type
- Thesis