Reduction of Annual Bluegrass, Poa annua, in Bentgrass Turf by the Use of Chemicals

HE great herbicidal developments of recent years give hope for Lchemical control of annual bluegrass, Poa annua, which is a miajor weed problem in bentgrass turf. Annual bluegrass produces an abundance of seed and quickly dominates bentgrass turf that is not growing at its optimum. Annual bluegrass might be controlled by prevention of seed set, pre-emergence control, and plant eradication. The original purpose of this study was to evaluate chemicals which offeredl promise of annual bluegrass control by checking seed set. However, necessity led to consideration of any promising chemical regardless of its method of control. No formal investigations of chemical treatment of annual bluegrass were available at the time this study was initiated. In 1955 the presence of arsenicals in the soil was reported to weaken the growth of annual bluegrass (2) and in 1958 fluorophenoxyacetic acids were reported to induce sterility in annual bluegrass for four to six weeks (1). Various golf course superintendents had used sodium arsenite in an attempt to suppress annual bluegrass.