ABSTRACT
There is no faster way to kill creeping bentgrass than with the misapplication of an herbicide (Figures 7.1 and 7.2). Most commercially available herbicides are known to discolor or severely damage creeping bentgrass and annual bluegrass, particularly on golf greens. Herbicides that normally are tolerated by creeping bentgrass and annual bluegrass may lose their margin of safety when applied during periods of heat or drought stress or when applied to turf grown in shaded or poorly drained sites where roots are restricted to the upper few inches (5 to 6 cm) of soil. Excessive soil wetness can intensify the toxicity of some herbicides. Creeping bentgrass maintained under low nitrogen fertility, excessive thatch-mat, lower than normal mowing height, or treated with plant growth regulators also is more susceptible to herbicide injury. There are few herbicides registered for use on creeping bentgrass, and even fewer for golf greens. It is important to note that the relative safety of labeled herbicides applied to vegetatively propagated, and many of the new seeded creeping bentgrass cultivars, is unknown. Even clones within a green may react differently to an herbicide or plant growth regulator treatment. Furthermore, there is little information on the relative tolerance of colonial (Agrostis capillaris) and velvet bentgrass (Agrostis canina) cultivars to herbicides. Field observations by golf course superintendents, and extension and U.S. Golf Association (USGA) agronomists often are our best sources of information on the tolerance of newer cultivars to chemicals, especially herbicides.
