Graduate Thesis Or Dissertation
 

Suppression of Microdochium Patch on Annual Bluegrass Putting Greens using Iron Sulfate, Phosphorous Acid, Sulfur, and Mineral Oil

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/sn00b4778

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  • Managing Microdochium patch on intensively manicured annual bluegrass putting greens is a challenge for turfgrass professionals in cool-humid climates similar to the Pacific Northwest. Fungicides are the predominant means to mitigate damage caused by this fungal pathogen, however pesticide restrictions are making it even more challenging to suppress Microdochium patch. Five field experiments, two growth chamber experiments, and two in vitro experiments were carried out to explore the use of iron sulfate heptahydrate, phosphorous acid, sulfur, and mineral oil on the suppression of Microdochium patch and on turfgrass quality. Mineral oil combined with either sulfur or phosphorous acid suppressed Microdochium patch, although combinations of mineral oil and sulfur reduced turfgrass quality, especially in the winter months. This reduction provides evidence that mineral oil and sulfur combinations should be avoided under similar conditions. Eliminating mineral oil applications in the winter months and replacing these applications with a sulfur and phosphorous acid combination suppressed Microdochium patch and mitigated damage although a temporary loss of turfgrass quality was still observed. Applying iron sulfate heptahydrate every two weeks suppressed Microdochium patch but resulted in suboptimal turfgrass thinning. Increasing the application interval of iron sulfate heptahydrate beyond two weeks decreased the level of Microdochium patch suppression observed. Increasing the water carrier volume of iron sulfate heptahydrate applications resulted in less abiotic damage quantified by having higher green cover percentages and these higher carrier volumes did not have a negative impact on Microdochium patch suppression. No benefit in Microdochium patch suppression was observed when adding iron sulfate heptahydrate to phosphorous acid applications compared to phosphorous applications alone, although turfgrass quality was improved when phosphorous acid was used in combination with some rates of iron sulfate heptahydrate. Both iron sulfate heptahydrate and phosphorous acid applications reduced the turfgrass surface pH for up to 17 days post application. Subsequent growth chamber and in vitro studies suggested that a reduction in pH was not solely responsible for the suppression in Microdochium patch by iron sulfate heptahydrate applications. These studies have demonstrated that multiple approaches of suppressing Microdochium patch are available to turfgrass managers and that future research is warranted in using these techniques as a part of an integrated pest management plan.
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  • Pending Publication
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  • 2020-03-09 to 2022-04-09

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