Postemergence Dallisgrass Control With Sequential Summer and/Or Fall Tank-Mix Applications.

Field experiments were conducted at the Pine Hills Golf Course in Winder, GA from 2012 to 2013 to investigate dallisgrass control with sequential tank-mix applications in summer and/or fall. The trial was located on a common bermudagrass rough (5.1 cm) with naturally occurring infestations of dallisgrass. The experimental design was a randomized complete block with four replications. Herbicide treatments were applied on August 31, 2012 followed by (fb) September 28, 2012 or September 28, 2012 fb November 2, 2012 and consisted of Tribute Total (thiencarbazone + foramsulfuron + halosulfuron) at 0.136 kg ai ha^-1 fb Tribute Total at 0.136 kg ai ha^-1, Celsius (thiencarbazone + iodosulfuron + dicamba) at 0.171 kg ai ha^-1 + Revolver (foramsulfuron) at 0.073 kg ai ha^-1 fb Celsius at 0.171 kg ai ha^-1 + Revolver at 0.073 kg ai ha^-1, Tribute Total at 0.136 kg ai ha^-1 + Dismiss (sulfentrazone) at 0.246 kg ai ha^-1 fb Tribute Total at 0.136 kg ai ha^-1 + Dismiss at 0.246 kg ai ha^-1, and Tribute Total at 0.136 kg ai ha^-1 + Celero (imazosulfuron) at 0.56 kg ai ha^-1 fb Tribute Total at 0.136 kg ai ha^-1 + Celero at 0.56 kg ai ha^-1. Each tank-mix application was applied with a methylated seed oil (MSO) at 0.5% v/v. Sequential applications of MSMA at 2.29 kg ai ha^-1 were only applied on August 31, 2012 fb September 28, 2012 and were included as an industry standard. A non-treated check was added in for comparison. Visual ratings of % bermudagrass phytotoxicity and % dallisgrass cover were recorded. Percent bermudagrass phytotoxicity was rated on a scale of 0 (no bermudagrass phytotoxicity) to 100% (complete bermudagrass desiccation) 1 and 2 weeks after each treatment (WAT). Percent dallisgrass cover was recorded monthly until December and again following spring green-up until the end of July 2013. Percent cover was compared back to dallisgrass cover recorded at the initiation of the trial and converted to % dallisgrass control. The only bermudagrass phytotoxicity (≤ 10%) was observed in response to MSMA. Plots fully recovered by 3 WAT. MSMA already began to exhibit regrowth 3 MAT (66% control). Long-term control (9 and 11 MAT) was 30 and 3%, respectively. All other treatments resulted in ≥ 93% control 3 MAT. August fb September applications increased the efficacy of all treatments 9 and 11 MAT compared to September fb November treatments. Tribute Total + Dismiss applied in August fb September resulted in the greatest long-term dallisgrass control (91%) 11 MAT. All other treatments applied in August fb September resulted in 64 to 71% dallisgrass control 11 MAT. All treatments applied in September fb November resulted in ≤ 68% dallisgrass control 11 MAT.