‘Tifdwarf Bermudagrass Growth Response to Carboxin and GA3 during Suboptimum Temperatures

Abstract

Carboxin at 0, 22, or 45 kg ha -1 and GA 3 at 0, 62, or 124 g ha -1 were evaluated as growth regulators on ‘Tifdwarf bermudagrass ( Cynodon spp.) putting greens during winter months. Turf response to both compounds was linear, but the magnitude of top-growth response was related to temperature. Bermudagrass response was greatest near its optimum temperature at 26° to 35°C. A single application of carboxin produced a 7-week response in top-growth clippings and GA 3 produced a 2-week growth response, even though weekly mean minimum air temperatures ranged from 8° to 19°C. Although significant growth responses occurred with both compounds, many growth rates were less than 25 kg ha -1 d -1 of fresh clippings, too low to sustain acceptable turf quality on putting greens. Carboxin and GA 3 have promise for improving turfgrass color under low traffic situations. Carboxin produced a blue-green turf in 5 or more days, and GA 3 produced a yellow-green turf in 1 to 2 days. Both compounds eliminated the purple cast commonly associated with ‘Tifdwarf bermudagrass turfs during suboptimum temperatures. Chemical names used: 5,6-dihydro-2-methyl- N -phenyl-1,4-oxathiin-3-carboxamide (carboxin); gibberellic acid (GA 3 ).