Selective Removal of Annual Bluegrass From Creeping Bentgrass Greens and Fairways with Cumyluron in Michigan.

Annual bluegrass (Poa annua L.) [AB] can be found anywhere in the world where human disturbance is present. AB is particularly a problem on golf courses where turfgrass managers endeavor to limit infestation into putting greens and fairways. Cumyluron is a substituted urea herbicide under development by Helena Chemical Co. for selective postemergence removal of AB in creeping bentgrass (Agrostis palustris H.) [CB]. Cumyluron was applied sequentially in the spring and fall to untrafficked, greens-height CB maintained at 3 mm and to untrafficked, fairway-height CB maintained at 1 cm. Visual observations were used to estimate the initial percent cover of the existing AB populations. Four levels of Factor A, herbicide rate, were used to represent 0, 0.5, 1, and 1.5X the proposed label rate for either green or fairway use. Factor B, application method, had three levels, herbicide only, surfactant tankmix, or immediate post-treatment irrigation. Both trials were conducted in 2007 in East Lansing, MI. Percent control was determined one year after initiation of the studies. Cumyluron applications resulted in 53-98 and 26-80 percent reduction of AB for the green and fairway trials, respectively. Percent control generally increased as application rate increased. The addition of a surfactant or immediate post-treatment irrigation did not result in improved annual bluegrass control in either trial as compared to cumyluron applied alone.