Thesis
Reducing the risk of onion bacterial diseases through irrigation and nitrogen fertility management
Washington State University
Master of Science (MS), Washington State University
01/2022
DOI:
https://doi.org/10.7273/000004571
Handle:
https://hdl.handle.net/2376/124850
Abstract
A comprehensive literature review indicates that managing onion bacterial diseases requires a holistic approach that integrates cultural management practices to address risk factors for infection and disease development. Late N fertilizer applications and available N in excess of plant requirements can make the plant more susceptible to bacterial diseases indirectly, by increasing the onion neck size, thus increasing time needed for the neck to dry or “cure” at the end of the season when the onion is most vulnerable to disease progression into the bulb. Moisture in the canopy is also a risk factor, and as such, overhead irrigation, ending irrigation too late in the season, or late-season rainfall can cause an increase in disease incidence by transferring bacterial inoculum through splashing water and by increasing the time needed for the plant to fully cure. Trials were conducted in the Columbia Basin of Washington State to assess the impact of irrigation and N management on onion bacterial disease incidence and severity, marketable yield, and bulb size distribution. Irrigating twice as frequently but for shorter time periods did not exacerbate onion bacterial diseases or affect yield under the conditions of this trial compared to longer, less frequent irrigation events. However, the timing of the final irrigation had a clear impact, as irrigating until 90% of the plants reached the “tops down” stage (after the final leaf emerges, when the neck naturally collapses) increased disease incidence after storage by 20.9% compared to ending irrigation earlier, at 10% tops down. Total available N rates in both 2020 (ranging from 217 kg N ha-1 to 396 kg N ha-1) and 2021 (ranging from 46 kg N ha-1 to 403 kg N ha-1) did not affect marketable yield or bacterial bulb rot incidence in either year, nor did the timing of the final N application, though elevated nitrate levels in the irrigation water, heat stress, and water stress may have limited the impact of N management. Nonetheless, adjusting N application rates to account for all N sources and managing irrigation carefully are recommended to minimize the risk of onion bacterial bulb rots.
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Details
- Title
- Reducing the risk of onion bacterial diseases through irrigation and nitrogen fertility management
- Creators
- Tessa Belo
- Contributors
- Gabriel T LaHue (Advisor)Lindsey J du Toit (Advisor)Timothy D Waters (Committee Member)Haly L Neely (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Agricultural, Human, and Natural Resource Sciences, College of
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University
- Number of pages
- 142
- Identifiers
- OCLC#: 1370910682; 99900898640801842
- Language
- English
- Resource Type
- Thesis