Centipedegrass is tolerant of both atrazine and mesotrione when applied separately to established turf. However, no information is available regarding the use of mesotrione or the synergistic mixture of atrazine plus mesotrione applied to centipedegrass during seeded establishment. Research was conducted to evaluate centipedegrass tolerance to various rates and combinations of atrazine plus mesotrione when applied 14 d after emergence (DAE). Experiment 1 evaluated centipedegrass tolerance to atrazine and mesotrione in a broad rate-range screen in a greenhouse environment. Variations were observed between greenhouse trial runs with respect to injury and biomass with less injury and decrease in biomass observed in run 2. Overall, atrazine alone and atrazine plus mesotrione were more injurious for a greater time period and decreased biomass more than mesotrione alone. In fact, although mesotrione alone initially reduced centipedegrass photosystem II efficiency, an overall increase in efficiency was observed 28 d after treatment (DAT). Based on experiment 1, atrazine at 0.28 kg ai/ha was the maximum rate that could be applied to seedling centipedegrass when tank mixed with mesotrione. Experiment 2 evaluated atrazine at 0.28 kg/ha plus mesotrione at 0.03 to 0.28 kg/ha on centipedegrass field establishment. Although all atrazine plus mesotrione treatments reduced centipedegrass ground cover 28 DAT; no treatment reduced centipedegrass ground cover 49 DAT.

Nomenclature: Atrazine; mesotrione; centipedegrass, Eremochloa ophiuroides Munro. (Kunz) ‘Tifblair’ ERLOP