Dr Fred Yelverton, North Carolina State University
Poa annua remains the most problematic weed on golf courses worldwide. Poa annua can be a desirable turfgrass species or it can be the worst weed. Typically in cooler climates, Poa annua is used as a desirable species. On golf courses, the battle is usually between creeping bentgrass and Poa annua. There are significant differences in growth parameters for the two species. In particular, creeping bentgrass is more heat and drought tolerant than Poa annua. Ironically, creeping bentgrass is also more cold tolerant than Poa annua. Due to the genetic diversity in Poa annua, different biotypes exist in a population. These biotypes differ in shoot density, color, heat tolerance, cold tolerance, as well as a range of other parameters. For these reasons, creeping bentgrass is usually the desired species. But in some environments, Poa annua populations are so high, it would require closing a golf course to renovate the putting greens. This is usually too intrusive and therefore, Poa annua becomes the species that is managed. New technologies to control Poa annua in creeping bentgrass may be coming on the market. One such product is methiozolin. However, this product is not “the solution” to all Poa annua problems. Plant growth regulators such as paclobutrazol are used to reduce Poa annua growth and promote creeping bentgrass growth. However, to rid an area of Poa annua with paclobutrazol requires multiple years of regular use.
