Evaluations of Single-Application Herbicide Efficacy for Control of Bermudagrass (Cynodon dactylon).

Bermudagrass (Cynodon dactylon) continues to be one of the most difficult grassy weeds throughout the US to control once it starts invading into undesirable areas. In most cases, multiple applications of herbicide active ingredients are required to manage aggressive regrowth from rhizomes and stolons following the initial application. Due to ever-present and ever-evolving issues with herbicide resistance throughout the US, research to evaluate the success of individual or combined herbicide active ingredients to manage bermudagrass in one primary application are greatly warranted. Greenhouse trials were conducted in 2016 and 2017 at New Mexico State University in Las Cruces, NM, to evaluate the efficacy of a single application on bermudagrass injury, control, and recovery through visual ratings, chlorophyll meter readings, and digital images analysis. Mature hybrid bermudagrass "Princess 77" cores were collected from an established field and allowed to acclimate to greenhouse conditions for at least two months prior to treatment application. Initial data indicates that 4% v/v glyphosate resulted in the most injury, and least recovery on bermudagrass. Injury from applications of 2% v/v glyphosate were enhanced by the addition of fluazifop (0.4 and 0.6 oz a.i. A^-1) and clethodim (16 and 32 oz a.i. A^-1). Additionally, applications of glyphosate or clethodim combined with fluazifop, mesotrione, or topramezone also provided successful control of bermudagrass. More research is necessary to evaluate treatments in field conditions and the timings/benefit of sequential herbicide applications.