Tolerance of Six Legumes to Common Turf Herbicides.

Herbicide options are limited for maintaining biodiverse turf-legume swards. Field and greenhouse experiments evaluated cool-season legume response to common turf herbicides during 2010 and 2011. Legumes, including white clover (Trifolium repens), small hop clover (T. dubium), rabbitfoot clover (T. arvense), crimson clover (T. incarnatum), ball clover (T. nigrescens), and spotted burclover (Medicago arabica), were transplanted into dormant bermudagrass (Cynodon dactylon) turf as randomized sub-units within main plots or were randomized twice weekly within a climate-controlled greenhouse. Main plot treatments included a control and these herbicide treatments: 2,4-D amine (15.8 g ae 100 m^-2), 2,4-DB amine (15.8 g ae 100 m^-2), dicamba (11.2 g ae 100 m^-2), MCPA (5.2 g ai 100 m^-2), triclopyr (5.6 g ai 100 m^-2), clopyralid (4.2 g ai 100 m^-2), bentazon (11.2 g ai 100 m^-2), metsulfuron-methyl (0.21 g ai 100 m^-2), trifloxysulfuron (0.28 g ai 100 m^-2), imazaquin (5.6 g ai 100 m^-2), and atrazine (22.4 g ai 100 m^-2). Herbicides were applied one month after transplanting. Visual injury was assessed weekly relative to the control. Height and dry-weight were assessed 6 weeks after treatment during 2011 only. A legume-species by herbicide interaction was observed for all assessments. Visual injury, dry weight, and height assessments generally concur. Burclover was less tolerant of 2,4-DB (>70% visual injury) than other clovers, while ball and white -clover injury was minimal (<30%). Rabbitfoot clover was partially tolerant of trifloxysulfuron; though, rabbitfoot clover MCPA injury (>90%) was greater than that of either crimson or hop clover (<60%). These results indicate varying tolerances between legume species and common turf herbicides; therefore, an even broader range of legumes and herbicides must be investigated in future research. More practically, these results indicate that herbicide options such as bentazon and 2,4-DB are viable weed control options within managed turf-legume swards.