Nutsedge And Kyllinga Control Strategies

Characteristics

Yellow nutsedge (Cyperus esculentus) is a perennial plant that reproduces by underground tubers called nutlets. A single plant can produce several hundred tubers in one season and they can persist for 10 or more years. Because of the proliferation of tubers, this weed can become a significant issue in just one summer. Yellow nutsedge will produce a seed if not mowed, but the seeds rarely germinate.

The growth rate of yellow nutsedge is what creates the greatest issue for golfers and turf managers. Patches of yellow nutsedge will often appear like they haven’t been mowed in weeks even when the surrounding turf is properly manicured. Not only does this have a negative impact on course aesthetics, playability and pace of play also suffer because of the difficulty involved in locating a golf ball and advancing it from a patch of nutsedge. This issue is highlighted during the summer when cool-season turf growth has slowed and nutsedge is firing on all cylinders.

Encroachment in the rough is not the only area of concern with yellow nutsedge. This weed tolerates low mowing heights and can be found on tees, putting green collars and fairways. Like when it is found in the rough, its rapid growth impacts playability and its pale green color is unsightly in closely mown turf areas.

Kyllinga (Kyllinga spp.) is also a perennial plant, but it encroaches in turfgrass environments through seed dispersal and the spread of underground rhizomes. This weed can be confused with yellow nutsedge, but it tends to form a denser patch of growth. The ability of kyllinga to tolerate low mowing heights makes it an issue for every playing surface on a golf course, including putting greens. Like yellow nutsedge, its growth rate can outpace the surrounding turf and cause aesthetic and playability issues.

For an area to drain properly, a combination of surface and internal drainage is required. Individual growing environments that are prone to invasion by nutsedge or kyllinga must be assessed to determine if internal drainage, surface drainage, or both must be improved to achieve the desired result.

Improper irrigation practices or uneven distribution of irrigation water can also create the saturated environments where nutsedge and kyllinga thrive. An evaluation of the soil profile, sprinkler run times and sprinkler operation must be completed to determine if too much water is being applied or if water distribution is uneven.

Maintaining a healthy, dense stand of turf is the best line of defense for limiting kyllinga and nutsedge encroachment, or any weeds for that matter. However, these hard-to-control weeds can still become an issue even if efforts are made to improve growing environments and maintain healthy turf. If small, isolated populations of these weeds are identified early enough, physical removal is an option. When this approach is implemented, it is imperative that all the underground reproductive structures are removed to prevent future issues. It must be noted that physical removal is a labor-intensive process. 

Chemical Control

Turf managers often resort to herbicides to control nutsedge and kyllinga once weed populations are too high to be controlled by physical removal. Traditional herbicides used to control broadleaf weeds and crabgrass have no impact on nutsedge or kyllinga. Specialty herbicides must be applied, and timing is critical to achieve control.

Both weeds are a nuisance in the middle of the summer. Unfortunately, when rapid growth is becoming unsightly and impacting playability, herbicide efficacy is marginal. Fall is the best time to control nutsedges and kyllinga because this is when translocation is enhanced to below-ground plant parts. Spring or early summer applications will also control both kyllinga and sedges to acceptable levels. Applications at this time will help reduce the spread of these weeds and limit the impact they have on playability and course aesthetics.

When developing a herbicide program to control sedges and kyllinga, include the following tactics:

• Plan to make treatments over multiple years. Rarely will one year of applications provide complete control.
• Map where sedges and kyllinga have been an issue so accurate repeat applications can be made.
• Rotate herbicides to reduce the likelihood of resistance.
• Ensure that soil moisture is adequate to support turf health but not excessive.
• Be aware of the mowing schedule, so that a recently applied herbicide is not removed by mowing.

Scientists from Purdue University suggests that postemergence controls be applied in the early summer, similar to preemergence timing, when plants are young and tubers undeveloped. There are several herbicides labeled for postemergence control of sedges, including kyllinga, for cool-season turf. Herbicides used for kyllinga control or suppression will also control nutsedge, but the reverse is not always the case. It is important to read every label and understand which products are used to control specific weeds. Table 1 lists herbicides that are commonly used to control kyllinga and nutsedge. For additional information on control of kyllinga and nutsedge in cool-season turf, review the article “Identifying and Understanding False-Green Kyllinga in Cool-Season Turf.” 

For preemergence control, the herbicides listed in Table 2 are effective at controlling nutsedge and kyllinga before they germinate on warm-season turf playing surfaces. Some of these products will also provide temporary suppression of emerging sedges. However, the flowable formulation of oxadiazon should not be applied to actively growing turf. If warm-season turf has broken dormancy, a granular formulation or fertilizer carrier should be used. Also, oxadiazon does not prune warm-season turf roots like several other commonly used preemergence herbicides. This is another reason turf managers choose this product.

One caveat to the preemergence herbicides listed in Table 2 is that field observations and research suggests that the older formulation of Specticle Flo caused turf damage on sandy soils. Thus, the rates have been adjusted for the new formulation, which is safe on all soil types. If your course has sandy soil and organic matter content is low – less than 1% – caution is needed to select the appropriate formulation for your site. 

Herbicide Resistance

Other field cropping systems have reported herbicide resistance in sedges, underscoring the importance of mode of action rotation. For example, farmers have reported ALS-resistant yellow nutsedge, rice flatsedge, small-flower umbrella sedge and others in row crops. Although row crops require different management than turfgrass, the herbicide use patterns are similar for superintendents. It is important that superintendents look to other agricultural industries and learn from their challenges, herbicide resistance being one of the most important. Without proper herbicide mode of action rotation, the risk of superintendents seeing similar herbicide resistance among sedge species will remain high.

Conclusion

Controlling kyllinga and nutsedge can be difficult, but it is possible. A combination of preemergence and postemergence herbicides should be utilized to ensure the highest possible chance of eradication. However, implementing the most consistent way to prevent these weeds from becoming a problem starts with sound agronomic programs. Maintaining a good growing environment with appropriate soil moisture levels are the best, and often cheapest ways to discourage weeds.