Reducing populations of annual bluegrass and roughstalk bluegrass in creeping bentgrass fairways: A nutritional approach

Two field studies, a seeded study and a golf course study, were conducted to compare competition among creeping bentgrass, annual bluegrass, and roughstalk bluegrass when subjected to common weed control practices and foliar applications of iron and magnesium. A research site was selected for the seeded study and divided into 10 whole plots receiving irrigation at either 50 or 100% evapotranspiration deficit. Each whole plot was further divided into subplots receiving one of seven treatments: bensulide, ethofumesate, trinexapac-ethyl, foliar Mg, foliar Fe, foliar Mg plus foliar Fe, and control. The site was seeded to a mixture of creeping bentgrass, annual bluegrass, and roughstalk bluegrass in September 1995, and treatments began in March 1996. Annual bluegrass was reduced 29% in plots treated with foliar Fe and 65% in plots treated with foliar Fe plus foliar Mg. Roughstalk bluegrass was significantly reduced in seeded plots treated with foliar iron (50%), plant growth regulator (75%), and foliar iron plus foliar magnesium (100%). Annual bluegrass and roughstalk bluegrass proportions were not affected by irrigation regime. In a second study, the most effective treatment, foliar magnesium plus foliar iron, was tested on a working golf course fairway and on a practice putting green beginning April 1997 and ending November 1997. Treatments on the golf course fairway and practice putting green were ineffective due to the established, perennial nature of the annual bluegrass biotypes on these sites. Further research is required to improve the efficacy of nutritional treatments on these perennials.