Fall Application Regimes of Methiozoline for Annual Bluegrass Corntrol in Creeping Bentgrass Putting Greens.

Field studies were conducted in New Jersey from 2010 to 2011 to evaluate the use of Methiozolin for annual bluegrass control in creeping bentgrass putting greens at Riverton, Metedeconk, and Charleston Springs Country Clubs. Methiozolin treatment regimes were 0.5, 1.0 and 2.0 kg/ha applied twice in Sept/Oct, Oct/Nov, and once in Nov. Methiozolin at 0.5 and 1.0 kg/ha were also applied three times in Sept/Oct/Nov. Annual bluegrass populations were high at Riverton (> 50%), low at Charleston Springs (<10%) and initially low at Metedeconk. However, by late Fall plots at Metedeconk averaged 30 to 40% annual bluegrass cover. Creeping bentgrass injury was not evident until the following March at all three locations.  At Charleston Springs, creeping bentgrass injury was 33 and 24% when methiozolin was applied at 2.0 kg/ha in Oct/Nov and Sept/Oct, respectively. but less than 10% with all other treatments. However, in late March creeping bentgrass injury increased to 65 and 30% with these two treatments. In addition, injury with all other treatments increased to 9 to 30%. At Metedeconck, creeping bentgrass injury was most evident in Late March with 60 and 80% injury observed when methiozolin was applied at 2.0 kg/ha in Sept/Oct and Oct/Nov, respectively. Injury with other treatments ranged from 10 to 60%. At both locations, creeping bentgrass recovered rapidly with 30% injury or less with all treatments in early May. Many treatments which had shown noticeable injury in late March had completely recovered by early May. Annual bluegrass control was 85% or greater at both locations when methiozolin was applied at 1.0 kg/ha or greater regardless of application timing. Similar results were observed at Riverton when methiozolin was applied at 1.0 kg/ha or greater. These studies suggest that methiozolin can effectively reduce annual bluegrass populations dramatically when applied in the Fall. Studies were duplicated at Charleston Springs and Howell Country Clubs with the elimination of the 2.0 kg/ha but similar treatment regimes.