CONTROL OF TURFGRASS WEEDS Lambert B. McCarty UNIVERSITY OF FLORIDA Tim R. Murphy UNIVERSITY OF GEORGIA INTRODUCTION A weed can be defined as any plant growing out of place or growing where it is not wanted. In a turf situation, for example, tall fescue 1 may be considered a weed when grown in a stand of bermudagrass or Kentucky bluegrass, but it is desirable when grown as a monoculture. Reasons for classifying a plant as a weed are numerous. In addition to being unsightly, weeds compete with turfgrasses for light, oxygen, soil nutrients, soil moisture, carbon dioxide and space. Weeds also act as hosts for pests such as plant pathogens, nematodes and insects. Certain weeds cause allergic reactions in humans due to their pollen or their volatile chemicals. Probably the most undesirable characteristic of weeds in turf is the disruption of the uniformity of a turf. Different leaf width and/or shape, different growth habit, and/or different color contribute to unsightliness. For example, many broadleaf weeds such as dandelion, plantains, and pennywort have leaf widths are different from turf. Goosegrass, smutgrass, and dallisgrass tend to form clumps or patches which disrupt turf uniformity. In addition, large clumps are difficult to mow effectively and they increase maintenance problems. Turf uniformity also is disrupted by weed seedheads. Annual bluegrass, for example, is largely unnoticed on putting surfaces until prolific seedheads appear in late winter and spring. These seedheads also disrupt the smoothness and trueness of the turf's playing surface (Fig.1). Plant color is a another factor in determining the potential of a weed problem in turf. The lighter green color typically associated with annual sedge often distracts from the playing surface. Bahiagrass often has different color when grown in combination with other turf species. 1 Common and scientific names of turfgrasses and weeds discussed are listed in Appendix A.