Smooth Bromegrass Control in Cool-Season Turfgrass.

Smooth bromegrass (Bromus inermis) is a difficult perennial grass to control in cool-season turf.  Currently there are few ways to control smooth bromegrass except with a non-selective herbicide such as (glyphosate). The objective of this research was to evaluate mesotrione, topramezone, and glyphosate for controlling smooth bromegrass at various times of the year.  In 2014, a field study was conducted using mesotrione at 8 floz/a applied twice 10 days apart, mesotrione at 5 floz/a applied three times 10 days apart, topramezone at 1.5 floz/a applied twice 10 days apart or glyphosate at 1.5 qt/a as a single application with an untreated control for comparison.  Herbicides were applied at three separate application timings May 1, June 1, and July 1 for a total of 4 treatments plus an untreated control and 3 application timings. Treatments were applied to a smooth bromegrass stand established the prior fall mowed to 3.5" weekly. Cover ratings of bromegrass were taken on a 0-100% range. At the end of the study on September 12^th 50 days after the final application 4 treatments resulted in lower bromegrass cover than the untreated.  Mesotrione applied at 5 or 8 floz/a on July 1 resulted in 8-20 % cover of bromegrass.  Mesotrione applied at 5 floz/a on June 1 resulted in 37% cover, and glyphosate applied at the same timing resulted in 23% cover of bromegrass.