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Cover Story
The Centipedegrass Conundrum – Holistic Approaches to Weed Control
By Jay McCurdy and Michael Richard,
Mississippi State University
Centipedegrass has become perhaps the most common low maintenance turfgrass species in the southeast. We can think of no other that has the breadth of utility in poor soils and areas with infrequent care. Unfortunately, its finicky response to routine maintenance means it sometimes gets “loved to death” by those responsible for its care.
Centipedegrass was first introduced in 1916 from Southeastern Asia. Seed were collected by the plant explorer Frank Nicholas Meyer (the namesake of ‘Meyer’ zoysiagrass and the ‘Meyer’ lemon) who was employed by the USDA’s Office of Seed and Plant Introduction. He drowned somewhat mysteriously near Shanghai in 1918 while exploring southeastern China via the Yangtze River.
There are at least eight species within the genus Eremochloa . Centipedegrass ( Eremochloa ophiuroides ) is the only one cultivated as a turfgrass species. Centipedegrass has many other common names. Chinese lawngrass or China grass denotes its origins. It is called cemetery grass due to its prevalence within cemeteries and poor man’s or lazy man’s grass because of its low maintenance requirements.
Centipedegrass is a warm-season, lime-green, medium-textured, slow growing grass found throughout the southeastern United States as low maintenance turf. It persists in humid-subtropical and tropical climates. Centipedegrass persists as far north as Tennessee and coastal Virginia; although, it is easiest to maintain where winter-time temperatures are mild. Centipedegrass is one of the least drought tolerant warm-season turf species. For this reason, it tends to do well in gulf-coastal environments due to timely rainfall during peak summertime temperatures.
drought conditions in the fall of 2016.
Centipedegrass varieties include ‘common,’ ‘TifBlair,’ ‘Oaklawn,’ and ‘Tennessee Hardy.’ Centipedegrass spreads by aboveground stems called stolons, as well as by seed. Seed take roughly three weeks to germinate and require adequate soil temperature to do so (approximately 80 degrees). Centipedegrass is commonly propagated vegetatively as sod but may also be established by sprigs or plugs.
Centipedegrass thrives in soils of moderate to low pH (between 5.0 and 6.0). Prior to establishing any turfgrass, a soil test should be performed in order to determine soil pH. Other site considerations should include shade, wear, and expectations. Centipedegrass persists in moderate shade better than bermudagrass but not nearly as well as St. Augustinegrass. Centipedegrass has poor wear tolerance and is slow to recover from injury because of its slow growth rate. Low fertility requirements and short statured growth make centipedegrass well suited for low to no mow scenarios, but property owners expecting thoroughbred performance will be unhappy with a plow-horse trod.
Once established, nitrogen inputs should be limited to less than 2 lbs nitrogen per 1,000 ft2 per year. By contrast, this is roughly half that recommended on low maintenance bermuda and zoysia grass lawns. When using controlled release nitrogen sources, I recommend even less. In some environments, nitrogen input may not be needed every year.
Some of the most experienced centipedegrass gurus suggest a potassium supplement in the spring and fall. Some folks use foliar apps of iron to correct the bleached appearance of grass grown in soils where pH is above optimal. The darker color lasts until the leaf tissue grows enough to be mown. Humic and fulvic acids, as well as various other soil amendments, are frequently suggested though research is scant in centipedegrass.
Centipedegrass does not have underground rhizomes like bermuda and zoysia grasses. When over fertilized, it becomes thatchy and prone to stress related decline. To prevent thatch, only fertilize when grass is actively growing, which in most southeastern lawns is after the third or fourth mowing event. Centipedegrass does well at a range of mowing heights (1 to 4-inches), but it does not recover well from scalping. Mowing low according to the 1/3rd rule during growing months helps promote lateral growth. Bag clippings if they accumulate or clump together and add them to your compost.
Holistic Weed Control
Unfortunately, centipedegrass does not conform to conventional herbicide applications as well as bermuda and zoysia grasses. Lawn care professionals who manage centipedegrass well are less governed by routine schedules and make decisions based upon concern for plant health rather than pest control. They scout and spot treat problematic areas. They run routes that are focused on sensitive species – centipede, St. Augustine, and carpet grasses. And most importantly, they educate consumers about expectations and appropriate cultural practices.
The essence of weed-free centipedegrass is dense, healthy turf. Centipedegrass is highly susceptible to herbicide injury during fall and spring transition periods, regardless of labelling. For instance, auxin mimicking herbicides (2,4-D, MCPA, dicamba, and others) are tolerated when turf is actively growing, but during fall and spring transition, centipedgrass is susceptible to injury and slowed growth.
Likewise, metsulfuron is labelled, but when applied during transition or even during mostly dormant winter conditions, injury and thinned stands are fairly common. When actively growing, phytotoxicity is transient, but during fall and spring dormancy or summer drought stress, even the slightest injury may push it over the edge.
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Figure 2. Herbicides applied in Biloxi, Mississippi on May 4, 2015. Spray volume was 40 gallons per acre. A non-ionic surfactant was included. Photos were taken 2 weeks after treatment. Notice slight turfgrass injury results from all treatments.
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Best management practices for centipedegrass weed control:
• Prioritize plant health. Manage fertility, soil pH, cultural practices, and especially thatch if you want a resilient centipedegrass lawn.
• Mow at a height that allows infrequent mowing. The higher the height of cut, generally the less frequent mowing.
• Rely upon fall preemergence herbicide applications for control of annual bluegrass and cool-season broadleaf weeds rather than winter/spring postemergence treatments. It is fairly typical to apply low rates of mitotic inhibiting herbicides (ex. Barricade, Pendulum, Dimension) in conjunction with simazine at a fall timing. Some practitioners apply reduced rates of Specticle in the Fall, but this is not advised unless dealing with extremely healthy centipedegrass. Ultimately, simazine and atrazine are the safest preemergence treatments for centipedegrass, but admittedly they lack the same spectrum of weeds controlled as many other preemergence options.
• With the exception of simazine or atrazine, we advise using decreased rates or forgoing the use of preemergence herbicides in the spring. Fly-away or looping stolons in lawns treated with mitotic-inhibiting herbicides or Specticle are typical. Gallery (isoxaben) might be another exception, as it tends to be very safe on grasses. Unfortunately, gallery lacks control of grassy weeds.
• Reduced rates of simazine and atrazine have long been standard recommendations for spring broadleaf/Poa control with the added benefit of some preemergence activity. For new customer accounts, a round-1 “clean-up” option is atrazine. Atrazine on a granular fertilizer carrier (ex. Scotts Bonus S) in spring is a standard that homeowners can do themselves.
• In general, avoid use of postemergence herbicides during spring and fall periods of static growth. Even though they’re labelled, products containing auxin mimicking herbicides (ex. 2,4-D, dicamba, mecoprop, clopyralid, and others) can be particularly problematic during periods of transition or slow growth. Herbicides are rarely the only cause of decline, but when combined with stress, such as drought or slowed recovery from winter, they too frequently result in thinned turf or stunted growth.
• When possible, spot treat postemergence herbicides rather than broadcast applying. We realize how impractical this can be, but so is re-sodding an entire yard.
Preemergence herbicides that are labelled include (but are not limited to):
• Barricade and others (prodiamine)
• Coastal (prodiamine, simazine, imazaquin)
• Dimension and others (dithiopyr)
• Gallery (isoxaben)
• Gemini (prodiamine, isoxaben)
• Echelon (prodiamine, sulfentrazone)
• Freehand (dimethenamid, pendimethalin)
• Kerb (pronamide)
• Pendulum and others (pendimethalin)
• Pennant Magnum (metolachlor)
• Specticle Flo (indaziflam) – Not for use in sod
• Surflan (oryzalin)
• Tower (dimethenamid)
Many postemergence herbicide labels limit or restrict use to periods of active growth. Several products (ex. Triplet-SF) limit application timings to dormant centipedegrass only. Our experience has been that centipedegrass green-up can be delayed even when applications are made according to label directions. Read the label and do not take risks when unnecessary. Products that are labelled include (but are not limited to):
• Aatrex (atrazine)
• Avenue South (penoxsulam, sulfentrazone, dicamba, 2,4-D)
• Banvel (dicamba)
• Basagran (bentazon)
• Blindside (metsulfuron, sulfentrazone)
• Celero (imazosulfuron)
• Celsius (thiencarbazone methyl, iodosulfuron, dicamba)
• Certainty (sulfosulfuron)
• Change-Up (MCPA, fluroxypyr, dicamba)
• Confront (triclopyr, clopyralid) –Not labelled for residential use
• Defendor (florasulam)
• Dismiss (sulfentrazone)
• Image (imazaquin)
• Katana (flazasulfuron)
• LockUp (penoxsulam, dicamba)
• Lontrel (clopyralid) –Not labelled for residential use.
• Manor, MSM-Turf, Rometsol, and others (metsulfuron)
• Princep 4L (simazine)
• Pylex (topramezone) - spot treatment only
• Quicksilver (carfentrazone)
• Relzar (halauxifen-methyl, florasuluam) –Centipede tolerance improved with addition of dicamba (0.12 to 0.24 lb ae/A)
• Sedgehammer, ProSedge, and others (halosulfuron)
• Segment (sethoxydim)
• Speedzone Southern (carfentrazone, 2,4-D, mecoprop, dicamba)
• Switchblade (halauxifen-methyl, fluroxypyr, dicamba)
• Tenacity (mesotrione)
• Trimec Southern (MCPA, 2,4-D, dicamba)
• Vista and/or Spotlight (fluroxypyr)
• Xonerate (amicarbazone)
Centipedegrass is tolerant of a few postemergence herbicides that are unique in warm-season turf. Only apply when turf is actively growing and is not under stress.
• Sethoxydim (Segment, Vantage) is labelled for grassy weed control at a reduced use rate. It will not control annual bluegrass or goosegrass, but it will control crabgrass with two applications roughly three weeks apart.
• The HPPD inhibitors mesotrione (Tenacity) and topramezone (Pylex) control crabgrass and goosegrass. Notice that Pylex is labelled for spot treatment only in residential centipedegrass.
• Winter-time applications of atrazine or simazine are sometimes applied for broadleaf and grassy weed control.
For whatever reason, crabgrass and goosegrass are rarely problematic in healthy centipedegrass. In our opinion, the most problematic weeds in centipedegrass are summer broadleaves that would exist regardless of spring preemergence application (ex. Virginia buttonweed, dichondra, dollarweed, common lespedeza, chamberbitter, and various sedges). Products that combine ALS inhibitors with auxin mimicking herbicides (ex. Celsius or Avenue South) or combinations of auxin mimicking herbicides (ex. Change-up, Trimec Southern, or Vista) plus low rates of metsulfuron are usually well tolerated during peak summer growth and result in fairly broad-spectrum control of broadleaf weeds. Sedgehammer, Celero, Katana, Image, Certainty, or Dismiss are all options for control of sedges.
St. Augustine and carpet grasses are frequently found in mixed stands with centipedegrass. Keep in mind that herbicide selection should account for the presence of these sensitive warm-season species. For instance, Celsius is labelled across a range of warm-season turf species, but it is a standard recommendation to control carpetgrass. Many an LCO has killed carpetgrass without knowing it was present.
Centipedegrass is susceptible to a number of pests other than weeds, including ground pearls, large patch, and nematodes. Proper pest identification is necessary in order to adequately treat these problems. Long term decline due to these or other pests may indicate that a site (or property owner) is not conducive to centipedegrass growth. Renovation and establishment of a more suitable grass species is a frequent recommendation.
In summary, use caution when applying herbicides to sensitive species, particularly centipedegrass. Prioritize plant health, and above all else, educate the consumer so that they have realistic expectations and perform cultural practices properly.
