Thesis
GERMINATION RESPONSE OF ANNUAL GRASS WEEDS TO GIBBERELLIC ACID 3 AND PREEMERGENCE HERBICIDES IN EASTERN WASHINGTON DRYLAND WHEAT PRODUCTION
Washington State University
Master of Science (MS), Washington State University
01/2022
DOI:
https://doi.org/10.7273/000004512
Handle:
https://hdl.handle.net/2376/125313
Abstract
Downy brome (Bromus tectorum) and Italian ryegrass (Lolium multiflorum) are problematic annual grass weed species in the dryland cropping regions of the Pacific Northwest (PNW). Traditional seedbank management methods in the PNW consist mainly of soil disturbance, an outdated practice with negative soil health implications. Reliance on herbicides introduced resistance, increasing weed control difficulty. Gibberellic acid (GA3) is a candidate for weed management as it stimulates germination of seed. Combined with preemergence herbicides, GA3 could improve chemical control efficacy while simultaneously reducing weed seedbanks. Studies were conducted at Washington State University, Pullman, WA and Davenport, WA in 2019 through 2022 to evaluate the germination response of B. tectorum and L. multiflorum to GA3. Two growth chamber studies evaluated germination response of new and old seed under various doses of GA3. Gibberellic acid did not impact germination of L. multiflorum regardless of seed age. A response was only observed in new B. tectorum seed when soaked in GA3. Four growth chamber studies evaluated the germination response of new and old seed sown and surface seeded in cold and warm growing environments. Highest germination was observed in seeds sown in cold temperatures, however GA3 had no impact. Two field studies were also conducted near Pullman, WA to assess GA3 combined with herbicides for management of L. multiflorum seedbanks. Gibberellic acid was applied preemergence to winter wheat with various preemergence herbicides followed by postemergence treatment of pinoxaden. Lolium multiflorum control was greatest when preemergence applications of pyroxasulfone or flumioxazin + pyroxasulfone + metribuzin were followed by a postemergence treatment of pinoxaden. Two field studies were conducted near Davenport, WA to assess GA3 combined with herbicide systems for management of B. tectorum seedbanks. Gibberellic acid was applied to winter wheat and fallow with combinations of preemergence herbicides, followed by a postemergence treatment of pyroxasulam. Bromus tectorum control was greatest when a preemergence application of pyroxasulfone + flumioxazin + metribuzin were followed by a postemergence application of pyroxsulam. Overall, the addition of GA3 did not improve B. tectorum or L. multiflorum control under field conditions.
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Details
- Title
- GERMINATION RESPONSE OF ANNUAL GRASS WEEDS TO GIBBERELLIC ACID 3 AND PREEMERGENCE HERBICIDES IN EASTERN WASHINGTON DRYLAND WHEAT PRODUCTION
- Creators
- Madisyn Renee Beaudoin
- Contributors
- Ian C Burke (Advisor)Drew J Lyon (Committee Member)Michael M Neff (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Crop and Soil Sciences, Department of
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University
- Number of pages
- 92
- Identifiers
- 99900877141101842
- Language
- English
- Resource Type
- Thesis