Tolerance to quinclorac by seedling creeping bentgrass

Annual grassy weeds often inhibit establishment of spring-seeded creeping bentgrass (Agrostis palustris Huds.) on golf courses. The objective of this experiment was to evaluate the safety of the annual grass herbicide quinclorac in spring-seeded creeping bentgrass in varying climatic regions of the United States. Experiments ere initiated in Indiana, Iowa, and North Carolina in Spring 2000. Treatments included siduron at 6.72 kg.ha(-1) a.i. applied immediately prior to planting (PRE), and quinclorac at 0.84 kg.ha(-1) a.i. applied 7 days before seeding (DBS), PRE, and 14 or 28 days after emergence (DAE). Herbicides were applied to three creeping bentgrass cultivars at each location. Siduron reduced establishment of 'Providence', 'L93', and 'Putter' creeping bentgrass in Indiana. Quinclorac applied PRE, 14 DAE, and 28 DAE caused short-term phytotoxicity, primarily in 'Providence' in Indiana. Quinclorac applications did not significantly affect cover of 'Providence', 'L93', or 'Putter' in Indiana or 'L93, 'Pennlinks', or 'Penncross' in Iowa. All applications of quinclorac reduced cover of 'L93', 'Pennlinks', and 'Penncross' in North Carolina. Though quinclorac applications resulted in no long-term damage when applied to creeping bentgrass seedlings in Indiana or Iowa, results from North Carolina indicate that caution should be exercised when using quinclorac on seedlings of creeping bentgrass. Chemical names used: 3,7-dichloro-8-quinolinecarboxylic acid (quinclorac); 1-(2-methylcyclohexyl)-3-phenylurea (siduron).