Coastal Bermudagrass (Cynodon dactylon) Yield Response to Various Herbicides

Abstract

Several new herbicides have been registered for pasture weed control, but their effect on ‘Coastal’ bermudagrass dry matter (DM) yield has not been documented. The objective of this study was to determine the effect of clopyralid, fluroxypyr, imazapic, picloram, picloram + fluroxypyr, picloram + 2,4-D amine, triasulfuron + dicamba, triclopyr amine + clopyralid, triclopyr ester, triclopyr ester + fluroxypyr, trifloxysulfuron, 2,4-D amine + dicamba, and 2,4-D ester on Coastal bermudagrass yield. Total DM yields of Coastal bermudagrass were not reduced by 0.84 kg/ha clopyralid, 0.031 kg ai/ha triasulfuron + 0.44 kg ai/ha dicamba, 1.205 kg ai/kg 2,4-D amine + 0.42 kg/ha dicamba, and 2.31 kg/ha 2,4-D ester. Although 0.227 kg ai/ha picloram + 0.84 kg/ha 2,4-D amine, 0.945 kg ai/ha triclopyr amine + 0.315 kg ai/ha clopyralid, and 1.68 kg ai/ha triclopyr ester reduced Coastal bermudagrass DM yields in harvest 1, there was no cumulative loss in total production in either 2001 or 2002 with these herbicides compared with that of the nontreated control. Coastal bermudagrass total DM yields were reduced by 52% with 0.158 kg ai/ha imazapic when applied to dormant bermudagrass in 2001, and by 26% with 0.021 kg ai/ha trifloxysulfuron when applied to actively growing bermudagrass in 2001; however, neither herbicide reduced total cumulative yield in 2002. In 2001 and 2002, total DM yield was reduced by an average of 25% with 0.42 kg/ha fluroxypyr, by 45% with 0.105 kg/ha imazapic, by 57% with 0.158 kg/ha imazapic, by 65% with 0.21 kg/ha imazapic, by 25% with 0.56 kg/ha picloram, by 20% with 0.188 kg/ha picloram + 0.188 kg/ha fluroxypyr, and by 18% with 0.63 kg/ha triclopyr ester + 0.21 kg/ha fluroxypyr, when applied to actively growing Coastal bermudagrass.