Foramsulfuron Effects on Emergence of Seeded Turf-Type Bermudagrass

Abstract

Several new sulfonylurea products have (or are being) brought to market for use in turf. One use of these products is for removing ryegrass from overseeded bermudagrass, since perennial ryegrass has become too persistent due to improvements in heat, drought, and close mowing tolerance. The soil half life of sulfonylurea is greatly increased in high pH soils, which are typical in the southwest. Superintendents may need to re-establish seeded bermudagrass after use of a S.U. transition agent if the underlying bermudagrass is sparse. With this in mind, a replicated field trial was conducted in summer 2004 to evaluate three rates of foramsulfuron (0.4, 0.8, 1.2 ounce /product/1000 ft2) herbicide at 0, 7, 14, and 28 days after seeding. Foramsulfuron is sold as Revolver. Revolver applied at time of seeding (0DAS) and 1 week after seeding (7 DAS) caused the greatest amounts of bermudagrass suppression in terms of bermudagrass plot cover and visible seedling vigor. When applied (7 DAS), bermuda cover (averaged over all three applied rates of Revolver) at 21, 28, and 36 DAS was 8%, 22% and 32% bermuda cover, respectfully, versus NTC mean values of 22, 49 and 54% cover, respectively. The second greatest degree of Bermuda suppression occurred from Revolver applied at the day of seeding (0 DAS). The effects lasted up until and included the end of the test on 29 Sept (36 DAS). When averaged over all 3 applied rates of Revolver, percent plot bermudagrass cover at 21, 28, and 36 DAS was 10%, 30% and 40% respectively for the 0 DAS treatments. The NTC cover for these same dates was 22%, 50% and 53% respectively. Vigor visual scores were minimal as well for all rates applied at (0 DAS) and at (7 DAS). Plots remained stunted up to 36 DAS for Revolver turfs applied at (7 DAS) and (0 DAS). Application at the time of seeding (0 DAS) resulted in more bermudagrass plot cover than if applied at (7 DAS). Rate reduction responses were realized only for Revolver application timings made at 0 DAS and 7 DAS (Table 1, 5, Figs. 1-4). No rate responses resulted for Revolver when applied at 14 DAS, 28 DAS. In conclusion, Revolver was safest when applied 14 DAS or later, with little rate effects.