Occurrence and control of weeds in sugarcane in Louisiana - exploring the use of triclopyr for bermudagrass management

Authors: ORGERON, ALBERT - LSU Agcenter; Spaunhorst, Douglas; GRAVOIS, KENNETH - LSU Agcenter

Submitted to: Proceedings of the International Society of Sugarcane Technologists
Publication Type: Proceedings
Publication Acceptance Date: 8/15/2019
Publication Date: 12/1/2019
Citation: Orgeron, A.J., Spaunhorst, D.J., Gravois, K.A. 2019. Occurrence and control of weeds in sugarcane in Louisiana - exploring the use of triclopyr for bermudagrass management. Proceedings of the International Society of Sugarcane Technologists. 30:299-306.

Interpretive Summary: Bermudagrass (Cynodon dactylon) is a major weed problem for Louisiana sugarcane producers, and few herbicides are available that control the weed once it is established within the crop. Once established, bermudagrass density and biomass increase and compete with sugarcane for essential resources. Field trials were conducted in Louisiana, USA during 2014-2018 to assess in-crop bermudagrass control with mixtures of topramezone plus triclopyr, and to evaluate the effect of these herbicides on sugarcane yield. In the first study, herbicide treatments were applied in March and included topramezone applied at 24.5 and 49 g/ha, topramezone + atrazine at 24.5 + 2240 g/ha, and topramezone + triclopyr at 24.5 + 1680 g/ha. At 28 days after application (DAA), topramezone plus triclopyr provided 85% bermudagrass suppression as compared to 46 and 54% for topramezone at 24.5 and 49 g/ha, respectively. A second experiment was conducted in 2017 and 2018, and herbicide treatments included mixes of topramezone + triclopyr at the following rates: 12.3 + 402, 12.3 + 804, 12.3 + 1210, 24.5 + 402, 24.5 + 804, 24.5 + 1210, 49 + 402, 49 + 804, and 49 + 1210 g/ha. Complete bermudagrass death was not observed, but weed suppression varied among treatments and ranged from 48 to 92% at 28 DAA. Bermudagrass suppression numerically increased as topramezone plus triclopyr rates increased. Topramezone at 49 g/ha + triclopyr at 1210 g/ha resulted in 92% bermudagrass suppression, whereas the topramezone at 49 g/ha + triclopyr at 402 g/ha treatment resulted in 68% bermudagrass suppression. No significant differences were observed for treatments for sugarcane stalk population, stalk height, sugarcane yield, sucrose content, or sugar yield. However, early season bermudagrass suppression from topramezone plus triclopyr resulted in numerical increases for stalk population, stalk height, sugarcane yield, and sugar yield when compared to the untreated check and would be a useful tool for Louisiana sugarcane producers.

Technical Abstract: Bermudagrass (Cynodon dactylon) is a major weed problem for Louisiana sugarcane producers, and control options, such as herbicide choices, are limited once the weed is established within the crop. Once established among sugarcane, bermudagrass density and biomass increase, often forming dense mats on the sugarcane bed. Field trials were conducted in Louisiana, USA during 2014-2018 to assess in-crop bermudagrass control with tank-mixtures of topramezone and triclopyr, and to evaluate the effect of these herbicides on sugarcane yield. In the first study, herbicide treatments were applied in March and included topramezone applied at 24.5 and 49 g/ha, topramezone + atrazine at 24.5 + 2240 g/ha, and topramezone + triclopyr at 24.5 + 1680 g/ha. At 28 days after application (DAA), topramezone + triclopyr provided 84.6% bermudagrass suppression as compared to 45.6 and 53.6% for topramezone at 24.5 and 49 g/ha, respectively. A second experiment was conducted in 2017 and 2018, and herbicide treatments included tank-mixes of topramezone + triclopyr at the following rates: 12.3 + 402, 12.3 + 804, 12.3 + 1210, 24.5 + 402, 24.5 + 804, 24.5 + 1210, 49 + 402, 49 + 804, and 49 + 1210 g/ha. Bermudagrass suppression varied greatly among the treatments and ranged from 48.3 to 92.0 % at 28 DAA. Percentage bermudagrass suppression numerically increased as topramezone and triclopyr rates increased. Topramezone at 49 g/ha + triclopyr at 1210 g/ha resulted in 92.0% bermudagrass suppression, whereas the topramazone at 49 g/ha plus triclopyr at 402 g/ha treatment resulted in 67.8 % bermudagrass suppression. No significant differences were noted among treatments for sugarcane stalk population, stalk height, sugarcane yield, sucrose content, or sugar yield. Stalk population, stalk height, sugarcane yield, and sugar yield were numerically greater that the untreated check and corresponded to bermudagrass suppression observed 28 DAA. An early-spring application of topramezone and triclopyr enhanced in-crop bermudagrass suppression in sugarcane and would be a useful tool for the Louisiana sugarcane producers.