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How to Manage Pests

Pests in Gardens and Landscapes

Green Kyllinga Published 4/03 In this Guideline:
Identification and life cycle Impact Management About Pest Notes Publication Glossary

Green kyllinga (Kyllinga brevifolia) is a weedy sedge that is becoming a major problem in turf and ornamental plantings in California. The genus Kyllinga consists of about 40 species that are distributed worldwide in subtropical and warm, temperate regions. Green kyllinga has been reported as a weed problem from Florida across the southeastern United States into Arizona, California, and Hawaii. In California it occurs from San Diego to the Sacramento Valley. Green kyllinga is believed to have originated in Asia and was reported as a weed in California over 50 years ago. In the last few years, however, it has developed into a major problem for turfgrass and landscape managers. Green kyllinga may be confused with yellow or purple nutsedge because they grow in similar locations. Often green kyllinga can be recognized by its habit of growing in continuously enlarging patches (almost as a turf). Yellow or purple nutsedge appear more commonly as individual plants. Also, green kyllinga has a small, round seed head whereas nutsedges have an open spikelet. The flower of the green kyllinga plant and the absence of underground tubers make it easy to distinguish from nutsedges.

IDENTIFICATION AND LIFE CYCLE

Green kyllinga is a perennial plant that grows best in moist or wet areas that receive full sun, but it can survive some shade and drying once established. Kyllinga grows well in warm weather from April through October. It is dormant in winter but remains green in warm climates where freezing does not occur. It may yellow in the winter but does not turn brown when it goes dormant. When left unmowed, green kyllinga can reach a height of about 15 inches. In areas that are mowed, it grows in a prostrate manner, producing a network of numerous underground stems (rhizomes). It roots and sends out leaves at each stem node. If green kyllinga rhizomes are removed and chopped into pieces, new plants can be produced from each node or stem section.

Leaves are long and narrow, ranging from 1 to more than 5 inches in length. Flowering usually occurs from May to October, but it can occur earlier in warm locations. Flower stalks are triangular in cross section and 2 to 8 inches in length. The stalks terminate in a globular inflorescence (flower) that is green and about 3/8 inch in diameter. Directly below the flower is a group of three leaves that radiate out from the stalk. There are 30 to 75 spikelets within each flower and each one is capable of producing one seed. A mature plant can produce over 100 flowers within a growing season and up to 5,000 seeds.

The seed of the green kyllinga plant is highly viable. It has an oval shape and is flat in cross section; it is about 1/8 inch long and 1/16 inch wide. Seed germination occurs at or very near the soil surface. Burying seed as little as 1/3 inch below the soil surface reduced germination 12-fold in one Arizona study. The tan-colored seed germinates when soil moisture is adequate and soil temperatures reach about 65°F. Germination continues throughout the summer. Seedling growth is slow initially and plants may require several weeks to become established. Once established, green kyllinga forms a vigorous system of rhizomes. It can survive and even flower and produce seed at mowing heights of 3/4 inch.

IMPACT

Green kyllinga can be a major weed problem for turfgrass and landscape managers. In turf it forms a weak sod that gives poor footing for athletic fields and golf courses. Although green kyllinga is most often a problem in bermudagrass, it has been found in cool-season turf species as well. Green kyllinga has a texture and color that varies from normal turfgrass species and reduces the aesthetic quality of the turf. Also, green kyllinga grows faster than most turfgrass species, which gives infested turfgrass an undulating or irregular surface in as little as 2 days after mowing.

Once a few plants become established in turfgrass or ornamental areas, spread can be rapid. In warm weather, rhizomes can grow by more than 1 inch per day, forming thick mats in just a few weeks. Seed and rhizomes are spread by mowing, foot traffic, and cultivation. This allows the production of new plants and hastens spread.

MANAGEMENT

The primary method of control is to prevent new infestations. Thoroughly clean mowers and cultivation equipment before moving from infested to weed-free areas. If solitary plants of green kyllinga are found, they should be grubbed out (i.e., remove the entire plant, roots and all) and the area monitored for several months to make sure that removal was complete. When green kyllinga infests ornamental plantings it forms a dense mat that crowds out desirable species and reduces the vigor of those plants that survive. Because of the extensive rhizome system in established stands, hand-pulling or hoeing to remove green kyllinga is usually futile unless done repeatedly over a long period of time. Thus control by this means is very expensive and not always successful. Areas with infestations should be isolated until control can be accomplished. Turfgrass and ornamental areas should be well maintained to promote maximum vigor and make these plantings as competitive as possible so that invasion by the weed is hindered. Dense turfgrass and ornamentals will shade the soil surface making the establishment of green kyllinga seedlings difficult.

Turfgrass

Controlling green kyllinga in turfgrass requires a combination of control procedures. Wet or overwatered areas in a turfgrass provide ideal habitat for a green kyllinga invasion. To reduce the chance of invasion or slow the invasion into turfgrass, do not overwater the turf. If low areas stay wet, improve drainage of that area.

Early grubbing of solitary infestations has been successful when practiced diligently. Spot-spraying isolated plants with glyphosate can be helpful, but the turfgrass is also killed, leaving open areas and making kyllinga reestablishment easier. The open spots should be overseeded to establish a vigorous turf.

Preemergent herbicides have been successful in limiting germination of green kyllinga seeds. These herbicides should be applied in spring before soil temperatures reach 60°F to limit germination in late spring and early summer. Preemergent materials that can be used by home gardeners include benefin, bensulide, dithiopyr, pendimethalin, and prodiamine.

Postemergent herbicides can limit growth of green kyllinga. For commercial applicators, the best control has been obtained when halosulfuron has been applied in two sequential applications. Apply the second application when plants show signs of recovering. Multiple applications of MSMA will reduce infestations (at least three applications at 14- to 21-day intervals are needed). Sequential applications of halosulfuron and MSMA have given the best control. Bentazon has reduced green kyllinga growth when two applications were made about 2 weeks apart.

Even when herbicides are used for control be sure that the turfgrass has adequate drainage to reduce the potential for proliferation by this weed.

Ornamental Landscapes

There are few options for the control of green kyllinga in ornamental landscape plantings. Prevention is very important. Hand-removal or spot-spraying of solitary plants will save time and money in the long run. Cultivation or hand-hoeing, although possible under some circumstances, is generally not useful and may be detrimental. Hoeing may break rhizomes into smaller pieces and "transplant" them to new areas. This is particularly true if irrigation follows hoeing. Geotextile mulches combined with hand-removal should provide adequate control in home gardens.

Mulching with landscape fabrics (geotextile mulches) can be effective if fabrics are overlapped and no light is allowed to penetrate to the soil. Use a polypropylene or polyester fabric or black polyethylene (plastic tarp) to block all plant growth. Wood chips or bark may be placed on top. Plant-derived mulches (organic mulches) alone may not effectively control kyllinga because it will probably grow through the mulch.

Preemergent herbicides such as oryzalin and pendimethalin can be used to limit seedling germination in sites where their use is permitted. Make applications in April before soil temperatures reach 60°F. Preemergent herbicides will be of little benefit if established kyllinga plants are present. Pendimethalin may be applied only by a licensed applicator in ornamental landscaped areas.

Few postemergent herbicides are registered for use in established ornamental plantings. Spot treatment with glyphosate can reduce green kyllinga’s growth, but do not let the spray come in contact with desirable plants or injury will result.

WARNING ON THE USE OF CHEMICALS

REFERENCES

Bryson, C. T. et al. 1997. Kyllinga, A genus of neglected weeds in the continental United States. Weed Tech. 11(8):838-842.

Kawabata, O., R. K. Nishimoto, and C. Tang. 1994. Interference of two kyllinga species (Kyllinga nemoralis and Kyllinga brevifolia) on bermudagrass (Cynodon dactylon) growth. Weed Tech. 8(1):83-86.

Molin, W. T. et al. 1997. Green kyllinga (Kyllinga brevifolia): germination and herbicidal growth. Weed Sci. 45(4): 546-550.

PUBLICATION INFORMATION

Pest Notes: Green Kyllinga
UC ANR Publication 7459        

Authors: D. W. Cudney, Botany and Plant Sciences Department, UC Riverside; C. L. Elmore, Vegetable Crops/Weed Science, UC Davis; D. A. Shaw, UC Cooperative Extension, San Diego; and C. A. Wilen, UC Cooperative Extension, San Diego
Editor: B. Ohlendorf
Technical Editor: M. L. Flint
Produced by IPM Education and Publications, University of California Statewide IPM Program

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