Postemergence Control of Lesser Swinecress In Creeping Bentgrass Putting Greens.

Lesser swinecress (Coronopus didymus (L.) Sm.) is a summer annual or biennial broadleaf weed that emerges from February to October with peaks of emergence in April and September. Tolerance to low mowing, heavy traffic, and prolific seed production has increased the prevalence of this weed in turfgrass environments. Field experiments were conducted at the Pecos County Municipal Golf Course in Fort Stockton, TX in the summer of 2011 to examine the postemergence control of lesser swinecress present in a creeping bentgrass putting green. Treatments were applied using a CO₂ backpack sprayer equipped with XR8004VS nozzle tips and calibrated to deliver 375 L/ha at 221 kPa. Treatments were initiated on May 31, 2011 and consisted of single or sequential applications of MCPP + 2,4-D + dicamba at 0.5 kg ae/ha, sulfentrazone at 0.14 kg ai/ha, and carfentrazone at 0.017 kg ai/ha. Sequential applications were made on July 5, 2011. Visual estimates of percent lesser swinecress control and creeping bentgrass phytotoxicity were recorded 1, 2, 4, 6, and 10 WAIT. Data were subjected to analysis of variance and means were separated using Fisher’s Protected LSD test at the 0.05 significance level. No creeping bentgrass phytotoxicity was observed throughout the length of the trial regardless of treatment or application timing. Lesser swinecress exhibited 0% control throughout the length of the trial in response to carfentrazone treatments. Control was only 19% 4 WAIT in response to single applications of sulfentrazone, but 88% in response to MCPP + 2,4-D + dicamba. A single application of sulfentrazone only provided 14% lesser swinecress control 10 WAIT, while a sequential application increased control to 41%. Lesser swinecress exhibited 91% control in response to a single application of MCPP + 2,4-D + dicamba, while sequential applications increased control to 100% 10 WAIT.