Kyllinga weeds defy some herbicides
Several species offer new challenges for superintendents
Todd Lowe; Bert McCarty, Ph.D.; and Ted Whitwell, Ph.D.
Sedges are common turfgrass weeds that favor warm climates and poorly drained or over-irrigated areas. Golf courses often provide ideal environments for sedges, where some of the more common species include purple nutsedge, yellow nutsedge, globe sedge, rice flat sedge, annual sedge and Kyllinga species (10).
Kyllinga species are becoming more prevalent on golf courses. Forty-five Kyllinga species exist, but only five are found in the continental United States, with one additional species occurring in Hawaii (6,7,9). Most are rather difficult to detect in turfgrass. Kyllinga leaves, however, are glossier than turfgrass leaves and are detected more easily in the morning when dew runs off their leaves while the turf remains wet. Kyllinga species also have a distinctive "minty sweet" scent when their leaves are mowed or crushed.
Kyllinga mats generally begin small (2-3 square feet) but may increase in size and choke out surrounding turfgrass.
Green kyllinga produces viable seed throughout the growing season. When unmowed, its seedheads are about the size of a garden pea and have a light green color. Seeds initiate germination in spring and continue throughout the summer.
A closely related perennial species is false green kyllinga (K. gracillima). It too is rhizomatous and about the same size as green kyllinga. False green kyllinga seedheads are less oval than those of green kyllinga. The major difference between these species is timing of seedhead production. Green kyllinga creates seedheads throughout the growing season, whereas false green kyllinga creates seedheads only in late summer or early fall.
Another perennial species in the continental United States is fragrant kyllinga (K. odorata). Fragrant kyllinga was once termed "annual kyllinga," but it is, in fact, a perennial species. Fragrant kyllinga is named for the sweet aroma it releases when its leaves are mowed or crushed.
Unlike the other mat-forming perennial species, fragrant kyllinga is tufted or bunchy rather than rhizomatous. Its seedheads are white and generally three-lobed, making them look like torpedoes or inverted Ys.
A species becoming more troublesome on golf courses is cock's comb kyllinga (K. squamulata). Cock's comb kyllinga is tufted but is larger than tufted kyllinga. Cock's comb kyllinga derives its name from its seed shape. Small spurs on the edge of the seed resemble a rooster's comb.
In fairways and roughs, cock's comb kyllinga is easily detected because it characteristically grows taller than the surrounding turf canopy. Cock's comb kyllinga plants also are generally light green or yellowish in color.
Treatments included one application of Barricade (prodiamine) at 0.75 pound of active ingredient per acre, Dimension (dithiopyr) at 0.5 pound, Pendulum (pendimethalin) at 3 pounds, Pennant (metolachlor) at 4 pounds, Ronstar (oxadiazon) at 2 pounds, simazine at 1.5 pounds and sulfentrazone at 0.5 pound. Sulfentrazone is an experimental herbicide under development by FMC. All treatments were liquid applications using 8004 flat fan nozzles at a rate of 30 gallons per acre.
Ronstar and sulfentrazone also provided good cock's comb kyllinga control (greater than 89 percent). Sulfentrazone offers good post-emergence green kyllinga and purple nutsedge control (2,8) but also has pre-emergence control activity. Pendulum, Dimension and Pennant provided 34-60 percent control. As expected, the dinitroaniline herbicides (Barricade and Pendulum) were ineffective at controlling either Kyllinga species.
Treatments were applied only once in our studies, and repeat applications may offer greater Kyllinga control.
Minimally acceptable bermudagrass injury (less than 20 percent) followed Ronstar and sulfentrazone applications at 1 and 2 weeks. No treatment injured turf beyond 3 weeks.
Barricade, Pendulum and Dimension are often used by golf course superintendents for pre-emergence control of annual grasses such as crabgrass. Although these herbicides may be less expensive, only slight Kyllinga control was observed at two months following treatment with these herbicides. This helps confirm the observations that Kyllinga species are becoming more prevalent on golf courses after prolonged pre-emergence herbicide use.
1. Blum, R.R., and F.H. Yelverton. 1997. Green
kyllinga (Kyllinga spp.) and purple nutsedge (Cyperus
esculentus) control in bermudagrass turf. Southern Weed
Science Society Proceedings 50:40.
Todd Lowe is a turfgrass research assistant at
Clemson (S.C.) University.