Response of Bentgrass Cultivars to Preemergence Herbicides

A field experiment was conducted over a 2-year period to evaluate the tolerance of five creeping bentgrass (Agrostis stolonifera L.) cultivars to preemergence herbicides. There was no herbicide-by-cultivar interaction. All herbicides applied at recommended rates maintained an acceptable quality (> 92% of untreated) throughout the spring and summer. Dithiopyr [.S,5-dimethyl-2-(di-fluoromethyl)-4-(2-methylpropyl)-6-(trifluoromethyl)-3,5-pyridinedi-carbothioate] at 0.43 kg ha−1 reduced quality 5% within two weeks after treatment, while oxadiazon {3-[2,4-dichloro-5-(l-methylethoxy) phenyl]-5-(l, l-dimethylethyl)-l,3,4-oxadia201-2-(3//)-one} at 3.4 kg ha−1 and bensulide [0,0-bis(l-methylethyl) 5-{2-[(phenylsulfomyl)-amino]ethy]phosphorodithioate} plus oxadiazon at 6.7 + 1.7 kg ha −1 reduced quality 8%. There was no difference in quality and density of creeping bentgrass when treated with bensulide plus oxadiazon at IX (6.7 + 1.7 kg ha−1) and 3X (20.2 + 5.0 kg ha-1) rates. The quality was similar when dithiopyr was applied at IX (0.43 kg ha l) and 3X (1.28 kg ha−1) rates, but density was lower during May and June at the higher rate. The quality and density of creeping bentgrass was lower for most of the spring and summer when treated with oxadiazon at 3X (10.1 kg ha −1) rate compared to the lX(3.4kgha−1) rate. ‘Cato’ and ‘Crenshaw’ creeping bentgrass cultivars generally maintained a higher turf quality than ‘Pennlinks’ and ‘Syn-G cultivars throughout the spring and summer and higher than ‘Penncross’ in August.