Master of Science (MS)


Plant, Environmental Management and Soil Sciences

Document Type



Torpedograss (Panicum repens L. Beauv.) is a common weed problem along the Gulf Coast in highly managed turf. Non-selective herbicides are currently used to control torpedograss within centipedegrass [Eremochloa ophiuroides (Munro) Hack.] and St. Augustinegrass [Stenotaphrum secundatam (Walt.) Kuntze], but turfgrass injury can be extensive. Research was conducted to evaluate torpedograss and centipedegrass response to the application of the selective, post-emergence herbicides quinclorac, sethoxydim, and clethodim. Quinclorac applied at 0.42 kg ai ha-1 three times 4 wks apart reduced torpedograss to 25% coverage (55% of control) 10 weeks after initial treatment (WAIT), but re-establishment was rapid and by 16 WAIT coverage was greater than that of the control. Centipedegrass injury to quinclorac was 46% 6 WAIT. Sethoxydim or clethodim applied at rates of 0.32 kg ha-1 or 0.30 kg ha-1, three times at 4 wk intervals reduced torpedograss coverage 79% and 84% from control 10 WAIT. Centipedegrass injury at 10 WAIT was 4% for sethoxydim and 13% for clethodim. Torpedograss treated with sethoxydim and clethodim was able to re-establish, and by 16 WAIT, groundcover was 25% and 26% compared to 59% for the control. Effects of N fertility and mowing height to reduce torpedograss infestation in centipedegrass and St. Augustinegrass were also examined. Nitrogen and mowing treatments were categorized as low, recommended and high according to each turfgrass species. For St. Augustinegrass, N fertility regimen were 0 kg N ha-1 month-1, 50 kg N ha-1 month-1, and 100 kg N ha-1 month-1and mowing heights were 2.54 cm, 6.35 cm, and 10.16 cm. Centipedegrass N fertility regimen were and 0 kg N ha-1 month-1, 12.5 kg N ha-1 month-1, or 25 kg N ha-1 month-1 with mowing heights of 2.54 cm, 5.08 cm, or 7.62 cm. Torpedograss spread increased in both turfgrasses under all N and mowing regimen. The highest mowing height accelerated torpedograss spread. Control of torpedograss in St. Augustinegrass and centipedegrass using cultural management practices proved unsuccessful. Some success in controlling torpedograss was attained with use of sethoxydim and clethodim in centipedegrass. Prevention by use of un-infested soils and application of non-selective herbicides during turfgrass establishment should be employed.



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Committee Chair

Jeffrey S. Beasley