Spring dead spot (SDS) is the most destructive disease of bermudagrass (Cynodon spp.) in Virginia. SDS infects bermudagrass in the fall with symptoms appearing in the spring when dormancy breaks. Patches are sporadically distributed but generally reoccur in the same location. Chemical control options are expensive with inconsistent results. Our objectives were to develop SDS incidence maps, investigate methods to analyze these maps, and evaluate suppression efficacy of incidence-map-based chemical applications. Methods were developed to build SDS incidence maps in 2016 and 2017. 2016 SDS incidence maps were compared for spatial accuracy to Digital Orthophoto Quarter Quadrangle (DOQQ), ground-validated differential GPS coordinates, and to 2017 SDS incidence maps, with average deviations of 1.3 m, 1.6 m, and 0.1 m, respectively. Digital Image Analysis (DIA) of aerial maps was compared to a point-intersect method for validation with a significant linear relationship (r2 = 0.77, P ≤ 0.0001). In the fall of 2016 and 2017, a site-specific penthiopyrad (SSP) treatment was evaluated against blanket, full-coverage applications of penthiopyrad (BP) and tebuconazole (BT), and an untreated control. Treatments were compared using DIA, post-treatment SDS patch count (PC), and SDS patch reduction (PR). Across all three metrics, the penthiopyrad treatments were statistically superior to both the tebuconazole and untreated. SSP compared favorably to BP for DIA, but BP had 2.57 fewer PC (LSD = 2.05) and a greater PR by 2.58 (LSD = 2.55). SSP using SDS incidence maps required 51% less fungicides in 2016 and 65% less in 2017 when compared to BP. / Master of Science in Life Sciences / Spring dead spot (SDS) is one of the most devastating diseases of bermudagrass in Virginia. Bermudagrass is utilized as a playing surface on golf courses and sports fields. During the fall, when the bermudagrass is preparing for winter dormancy, SDS can infect and reduce the turf’s cold tolerance. As a result, dead patches are present in the spring of the year. SDS ruins the integrity of playing surfaces and is slow to recover. The objectives of this research were to develop SDS incidence maps, investigate methods to analyze these maps, and evaluate site-specific chemical applications to control SDS, based on historical incidence. We developed methods for building SDS incidence maps in 2016 and 2017. Maps were evaluated for spatial accuracy as well as their ability to differentiate SDS from healthy bermudagrass. Digital Image Analysis (DIA) was used to calculate SDS coverage. DIA utilizes pixel color values to distinguish SDS from healthy turf. In the fall of 2016 and 2017, a site-specific penthiopyrad (SSP) treatment was evaluated against two full-coverage, blanket fungicides in penthiopyrad (BP) and tebuconazole (BT), as well as an untreated control. These programs were analyzed and across three metrics, DIA, Patch Count (PC) and Patch Reduction (PR), the penthiopyrad treatments were statistically superior to both the tebuconazole and untreated. SSP compared favorably to BP for DIA, but blanket applications were statistically superior when analysis by PC and PR. SSP required 51% less fungicides in 2016 and 65% less in 2017 when compared to BP.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/83499 |
| Date | 08 June 2018 |
| Creators | Booth, Jordan Christopher |
| Contributors | Plant Pathology, Physiology, and Weed Science, McCall, David S., Askew, Shawn D., Baudoin, Antonius B., Goatley, James Michael |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Thesis |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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