A new herbicide for weeds in bermudagrass and zoysiagrass - GCSAA

A new herbicide forweeds in bermudagrassand zoysiagrassRESEARCHControlling cool-season grasses and weeds in bermudagrass andzoysiagrass just got a little easier.Fred Yelverton, Ph.D.Recently, the EPA approved a new herbicidefor post-emergence control of variousweeds commonly found on golf courses andsod farms. Foramsulfuron (sold under thetrade name Revolver) is currently registeredfor use only on zoysiagrass and bermudagrass,including bermudagrass puttinggreens. To date, this product is approved foruse on common, Tifway, Tifgreen, Tifsport,Tifdwarf and Vamont bermudagrasses, andMeyer zoysiagrass. Turfgrass managersshould test the product before using it onother cultivars.What is foramsulfuron?Foramsulfuron belongs to a relativelynew family of herbicides known as the sulfonylureas.Sulfonylurea herbicides are characterizedby selective, post-emergencecontrol of grasses and broadleaf weeds inturf, forestry, horticultural and field crops.Members of this family of herbicides are alsoknown for being highly selective (forinstance, they are highly effective on theweeds they control, but the number of weedspecies controlled is small compared to olderherbicides). They are also known for havinglow use rates. Several other sulfonylurea herbicides,including chlorsulfuron (Corsair),halosulfuron (Manage), metsulfuron (Manoror Blade) and rimsulfuron (TranXit GTA),are registered for use on golf courses.Unlike other sulfonylureas, foramsulfuronis sold as a liquid formulation. Its userates are also higher than those of other sulfonylureas,although the pounds of activeingredient per acre are still quite low. Coolseasonturfgrasses have some tolerance tochlorsulfuron, halosulfuron and metsulfuron,but they have no tolerance to foramsulfuron.Foramsulfuron, therefore, willThree weeks after treatment, plots with Revolver applied at 0.2 ounce per 1,000 square feet (left) still had perennialryegrass, whereas in plots where Revolver was applied at a higher rate of 0.4 ounce per 1,000 square feet (right),much of the perennial ryegrass was already dead or dying.never be used on cool-season grasses unlessthey need to be removed from bermudagrassKEY pointsMore Info: www.gcsaa.orgThe EPA has approved a new herbicidethat controls weeds and removes coolseasongrasses in overseeded andnonoverseeded bermudagrass andzoysiagrass.Foramsulfuron (Revolver) is known tocontrol annual bluegrass, rough bluegrass,perennial ryegrass, tall fescue,creeping bentgrass, goosegrass, centipedegrassand henbit.Foramsulfuron removes overseededperennial ryegrass very quickly.or zoysiagrass. In fact, removal of cool-seasongrasses from warm-season grasses will likelybe one of the major uses of foramsulfuron.Revolver will be sold as a suspension concentratecontaining 2.34 percent or 0.19pound active ingredient per gallon of foramsulfuron.The label carries the signal word“Caution,” which places it in the least toxiccategory for pesticides. (Signal words areordered from “Caution” to “Warning” to“Danger,” with Caution the least toxic andDanger the most toxic.) Foramsulfuron isnot a restricted-use pesticide.Weeds controlled by foramsulfuronAnnual bluegrass (Poa annua), roughbluegrass (P. trivialis), perennial ryegrass(Lolium perenne L.), tall fescue (Festuca arundinaceaSchreb.), creeping bentgrass (AgrostisPhotos courtesy of Fred Yelverton

RESEARCHstolonifera) and other cool-season grasses arecontrolled by foramsulfuron, as are goosegrass,centipedegrass and henbit. Becauseforamsulfuron is new, the complete spectrumof weeds controlled is not yet known.However, research has shown that the abovementionedspecies are effectively controlled.The rates will range from 0.1 to 0.6ounce/1,000 square feet or 4.4 to 26.2ounces/acre.It is recommended that foramsulfuron beapplied in at least 25 but not more than 60gallons of water per acre. If the pH of thespray solution is less than 6, a buffering agentis recommended. As with any herbicide, certainprecautions should be followed. The followingare the most notable:• Apply to actively growing weeds. WeedsFORAMSULFURON VS. WEEDSunder stress (drought, etc.) will not be controlledeffectively.• Rainfall within two hours after applicationmay reduce control.• Do not use more than 1.25 ounces/1,000square feet (54.5 ounces/acre) per season.• Apply foramsulfuron within 24 hours ofmixing.• Do not apply foramsulfuron within twoweeks of bermudagrass sprigging.• Do not apply foramsulfuron within twoweeks before overseeding bermudgrasswith cool-season grasses.• Avoid excessive aerification and verticuttingwithin one week of application.• Do not use on residential turf.• Do not collect grass clippings for mulchor compost.Application rate*Species controlled Ounce/1,000 square feet Ounces/acrePerennial ryegrass 0.2, 0.4 8.8, 17.4Volunteer perennial ryegrass,tall fescue & other cool-season grasses 0.2, 0.4, 0.6 8.8, 17.4, 26.2Poa annua 0.2, 0.4 8.8, 17.4Poa trivialis, P. annua, & creepingbentgrass in overseeded bermudagrassgreens, tees, collars & approaches 0.1, 0.2, 0.4 4.4, 8.8, 17.4Goosegrass 0.4, 0.6 17.4, 26.2Centipedegrass 0.6 26.2Henbit 0.4 17.4*Multiple applications may be required for goosegrass, volunteer perennial ryegrass or where the rate of 0.1ounce/1,000 square feet rate is used. For goosegrass, two applications spaced seven to 14 days apart are recommended.The lower rate may be used for goosegrass in the one- to three-leaf stage, but the higher rateshould be used on goosegrass with one to three tillers.Research with foramsulfuronUniversity researchers have tested foramsulfuronfor the past three years. Theremoval of perennial ryegrass (and otheroverseeded cool-season grasses) frombermudagrass has been investigated extensively,and there is little doubt that foramsulfuronwill be effective for this use. Thedata shown here are representative of threeyears of research at multiple locations.Removing perennial ryegrassIn a test conducted at PrestonwoodCountry Club in Cary, N.C., foramsulfuronwas very effective in removing perennial ryegrassfrom a fairway. Foramsulfuron appliedat 0.4 or 0.6 ounce/1,000 square feet essentiallyremoved the perennial ryegrass in fourweeks (86 and 89 percent control, respectively).In this test, the lowest rate of foramsulfuronwas not effective in removingperennial ryegrass.Metsulfuron (Manor) was effective inremoving perennial ryegrass and is considereda standard treatment for this purpose,but, as the data indicate, metsulfuron did notact as quickly as foramsulfuron to killperennial ryegrass. Note that as early as threeweeks after treatment (when these pictureswere taken), the perennial ryegrass in foramsulfuron-treatedplots looked dead. The onlyturf visible in these pictures is the underlyingbermudagrass.Speed of controlIn general terms, the speed at which herbicidescontrol perennial ryegrass is not considereda negative or a positive. Individualsuperintendents need to determine the speedat which they want to control perennial rye-REMOVAL OF PERENNIAL RYEGRASSRate% perennial ryegrass controlTreatment (ounce/1,000 square feet) (ounces/acre) 2 WAT 4 WAT 8 WATForamsulfuron 0.2 9 49 23 60Foramsulfuron 0.4 18 58 86 100Foramsulfuron 0.6 28 55 89 100Metsulfuron 0.01 0.5 50 40 85WAT = weeks after treatment.Removal of perennial ryegrass from an overseeded bermudagrass fairway at Prestonwood CC, Cary, N.C., 2001. Applications were made May 7, 2001. Mowing height was0.5 inch. A nonionic surfactant at 0.25 percent volume/volume was added to metsulfuron.

RESEARCHPoa annuaIn nonoverseeded bermudagrass, foramsulfuroncan also be used to control annual bluegrass(P. annua). Annual bluegrass control innonoverseeded bermudagrass can be difficult inareas where bermudagrass does not go completelydormant. Where bermudagrass does gocompletely dormant, glyphosate (Roundup,etc.) can be used for annual bluegrass control,but it cannot be used in areas that fail to go dormant.Therefore, foramsulfuron can be an effectivemanagement tool for golf coursesuperintendents who cannot use glyphosate.Foramsulfuron removed annual bluegrasseffectively, but it took approximately 10weeks to get complete control. Foramsulfuronwas as effective as glyphosate in removingannual bluegrass from bermudagrass.SummaryIn summary, foramsulfuron will be an additionaltool for the management of certain weedsfor turfgrass managers with bermudagrass andzoysia. It is highly toxic to cool-season turfgrassspecies and, therefore, will be an effective tool forremoving overseeded cool-season turfgrass speciesfrom bermudagrass. A common question thatwill arise is the safety of foramsulfuron aroundcreeping bentgrass putting greens or other desirablecool-season grasses. Foramsulfuron is a sulfonylurea,and most members of the herbicidefamily will move laterally given favorable conditionsfor movement (for instance, significantrainfall soon after herbicide application when soilconditions are already saturated). Therefore, donot apply foramsulfuron up-slope of desirablecool-season turf.Foramsulfuron will also be useful in removingannual bluegrass from nonoverseededbermudagrass or zoysiagrass. It can also effectivelycontrol goosegrass, but repeat applicationsare usually necessary. Additional research anduse by superintendents will help identify additionalweeds controlled by foramsulfuron.NontreatedRevolver 0.4 ounceApplied at 0.4 ounce/1,000 square feet, Revolver controlled clumpy perennial ryegrass effectively (foreground). Theuntreated area is in the background of the photo.AcknowledgmentsThis research was funded in part by the North CarolinaTurfgrass Foundation.References1. Bayer Environmental Science. Revolver productlabel. Bayer Environmental Science, Montvale, N.J.2. McCarty, L.B. 2002 Turfgrass Research Report.Clemson University, Clemson, S.C.3. Yelverton, F.H., L. Warren, T. Gannon and J. Hinton.2001 Turfgrass Research Report. North CarolinaState University, Raleigh.Fred Yelverton, Ph.D., is an associate professor andExtension specialist at North Carolina State University,Raleigh.CONTROL OF CLUMPY PERENNIAL RYEGRASSRate% control clumpy perennial ryegrassTreatment (ounce/1,000 square feet) (ounces/acre) 2 WAT 4 WAT 8 WATForamsulfuron 0.4 18 0 83 95Metsulfuron 0.02 1.0 0 74 93WAT = weeks after treatment.Effects of foramsulfuron and metsulfuron on control of clumpy perennial ryegrass, Sandhills Research Station, Jackson Springs, N.C., 2001. Applications were made July13, 2001. A nonionic surfactant at 0.25 percent volume/volume was added to metsulfuron.POA ANNUA CONTROLRate% perennial ryegrass controlTreatment (ounce/1,000 square feet) (ounces/acre) 3 WAT 6 WAT 10 WATForamsulfuron 0.4 18 0 38 60Glyphosate 0.37 16 0 69 89WAT = weeks after treatment.Control of annual bluegrass (Poa annua) in nonoverseeded bermudagrass, Quail Ridge GC, Sanford, N.C., 2001. Applications were made on Dec. 18, 2001; annual bluegrasswas in the zero- to two-tiller stage.