Seeded bermudagrass response to herbicides during ... - GCSAA

Although injury to bermudagrass fromthese herbicides is physiologically interestingbecause these herbicides are primarily activeon dicotyledonous broadleaf plants, suchinjury has been reported previously for establishedbermudagrass turf. Repeat applicationsof Confront have been reported to causeinjury levels of 30%-40% to common, Tifwayhybrid and Tifeagle hybrid bermudagrasses(6). Bermudagrass injury from products containingtriclopyr is so significant that triclopyris often used in spray mixes with fenoxapropor fluazifop for selective removal of bermudagrassfrom tall fescue (Festuca arundinacea) andRESEARCHzoysiagrass (Zoysia species) (3).Similar trends were observed for theeffect of herbicides for broadleaf weed controlon common bermudagrass cultivar groundcover (Table 2). The low and high rates ofConfront reduced ground cover compared tothe nontreated plots for all cultivars 21 days% GROUND COVER VS. HERBICIDESPrincess 77 Riviera Savannah YukonDays after intial treatment21 42 21 42 21 42 21 42Rate Application timingHerbicide (metric units) (DAIT)% cultivar ground cover*AAtrex 2.0 quarts/acre 0 24 d 79 c 29 d 88 abc 26 d 75 b 4 f 25 e(4.7 liters/hectare)Millennium Ultra (low) 1.25 pints/acre 0 68 ab 84 b 80 a 92 abc 82 a 97 a 29 d 59 cd(1.5 liters/hectare)Millennium Ultra (high) 2.5 pints/acre 0 68 ab 85 b 65 bc 87 bc 81 a 95 ab 29 d 61 bcd(2.9 liters/hectare)Trimec Classic (low) 1.75 pints/acre 0 76 ab 89 ab 68 bc 85 c 83 a 97 a 41 c 62 bcd(2.0 liters/hectare)Trimec Classic (high) 3.5 pints/acre 0 63 bc 91 ab 71 bc 89 abc 80 a 97 a 31 d 64 bc(4.1 liters/hectare)Revolver 17.4 fl oz/acre 0 82 ab 94 ab 84 a 97 ab 84 a 95 ab 48 ab 76 a(1.3 liters/hectare)MSMA (low) 1.35 fb 1.35 pints/acre 0 fb 7 71 ab 99 a 82 c 99 a 82 c 97 a 53 a 81 a(1.6 fb 1.6 liters/hectare)MSMA (mid) 2.0 fb 2.0 pints/acre 0 fb 7 80 ab 99 a 82 a 98 ab 82 a 97 a 39 c 81 a(2.3 fb 2.3 liters/hectare)MSMA (high) 2.65 fb 2.65 pints/acre 0 fb 7 78 ab 99 a 79 ab 99 a 80 a 93 ab 43 b 80 a(3.1 fb 3.1 liters/hectare)Drive 1.0 lb/acre(1.1 kilograms/hectare) 0 79 ab 100 a 72 b 99 a 84 a 97 a 25 d 71 ab+ 1.5 pints/acre(1.8 liters/hectare) of MSOConfront (low) 1.0 pints/acre 0 51 c 89 ab 69 bc 94 abc 66 b 92 ab 16 e 55 c(1.2 liters/hectare)Confront (high) 2.0 pints/acre 0 43 c 91 ab 66 bc 88 abc 41 c 86 ab 11 ef 51 d(2.3 liters/hectare)Monument 0.47 ounces/acre 0 75 ab 97 ab 62 c 95 abc 83 a 93 ab 29 d 63 b(32.9 grams/hectare)+ 0.25% v/v NISNot treated — — 81 ab 91 ab 82 a 97 ab 83 a 97 a 55 a 71 ab*Different letters within the same column indicate significant differences in % ground cover among treatments for the same cultivar.Note. Treatments applied from four to seven weeks after emergence at the onset of uniform stolon development. Percent bermudagrass ground cover rated on ascale of 0 to 100, where 0 equals bare ground and 100 equals no exposed soil. Abbreviations: DAIT, days after initial treatment; fb, followed by; MSO, methylated seedoil surfactant; NIS, non-ionic surfactant.Table 2. Percent green turf coverage by the seeded bermuagrass cultivars 21 and 42 days after initial treatment (DAIT) applied four to seven weeks after seedlingemergence when cultivars begin stolon development.January 2005GCM 157

RESEARCHafter initial treatment. However, by 42 daysafter initial treatment, all cultivars exceptYukon recovered to a level similar to that ofthe nontreated plots. This further illustratesthat Yukon is generally more susceptible toherbicides during seedling establishment.The low and high rates of Trimec Classicand Millennium Ultra reduced Yukon groundcover compared to the nontreated plots 21days after initial treatment. However, by 42days after initial treatment, ground cover forYukon was similar to that for nontreated turf.A similar trend was observed for Rivieratreated with high rates of Trimec Classic andMillennium Ultra and for Princess 77 treatedwith low and high rates of Trimec Classic.Response to Revolver and MonumentRevolver did not injure (Table 1) orreduce ground cover (Table 2) of any cultivarevaluated at any rating date. The only adverseeffect of Monument was a reduction inRiviera and Yukon ground cover at 21 daysafter initial treatment; at 42 days after initialtreatment, both cultivars had ground coversimilar to that of nontreated turf.Repeat applications of Revolver andMonument have been previously reported tocause little to no injury to established bermudagrassturf (2,8). No direct comparison can bemade to seedling bermudagrass tolerance tothese herbicides. However, the sulfonylureaherbicide, Manor (metsulfuron), has beenreported to cause greater injury to Jackpot,Mirage and Numex Sahara than 2,4-D,dicamba, Lontrel (clopyralid) and Drive (7).Further research is needed to evaluate potentialtolerance differences to sulfonylurea herbicidesamong common bermudagrass cultivars.THE RESEARCH says . . .Repsonse to MSMA and DriveIn general, the effects of the MSMA andDrive treatments in terms of turfgrass injury orground cover reduction were similar to the nontreatedcontrol. However, at 14 days after initialtreatment, injury to Yukon from Drive and thehigh rate of MSMA was greater than the injuryin the nontreated plots (Table 1). Slight injuryfrom Drive to seedling common bermudagrasscultivars and subsequent recovery by 30 days afterinitial treatment has been reported previously (7).These authors also reported that five commonbermudagrass cultivars (Jackpot, Mirage, NuMexSahara, Princess 77 and Yukon) did not differ intheir response to MSMA or Drive.At 21 days after initial treatment, Driveand mid and high rates of MSMA reducedYukon ground cover compared to the nontreatedplots. By 42 days after initial treatment,Yukon had recovered from thesetreatments. At 21 days after initial treatment,Drive reduced Riviera ground cover comparedto the nontreated plots. Riviera recoveredfrom these treatments by 42 days after initialtreatment. MSMA and Drive did not reduceground cover of Princess 77 or Savannah comparedto the nontreated plots at 21 or 42 daysafter treatment. Sequential applications ofMSMA at 2.7 pints/acre (2.2 kilograms activeingredient/hectare) can injure fully establishedbermudagrass turf, but injury usually does notexceed 30%, and the bermudagrass fullyrecovers in two to four weeks.ConclusionsThe application safety of herbicides variedamong the four bermudagrass cultivars, withYukon being generally more susceptible toinjury than the other cultivars. AAtrex shouldnot be applied to any of the cultivars we evaluatedat or before uniform stolon development,approximately four to seven weeks afterseeding. Various herbicide pre-mixtures containing2,4-D, mecoprop, dicamba, clopyralidor triclopyr should be used with caution whenapplied at or before stolon development.Revolver, MSMA, Monument and Drive aregenerally safe for the four cultivars evaluated.Although we observed some injury at 14 daysafter initial treatment and reduced groundcover at 21 days after initial treatment withthese herbicides, all cultivars recovered by 42days after initial treatment.Literature cited1. Bunnell, B.T., R.D. Baker, L.B. McCarty, D.W. Hall andD.L. Colvin. 2002. Differential response of five bahiagrass(Paspalum notatum) cultivars to metsulfuron.Weed Technology 17:550-553.2. Busey, P. 2004. Goosegrass (Eleusine indica) controlwith foramsulfuron in bermudagrass (Cynodonspp.) turf. Weed Technology 18:634-640.3. Cudney, D.W., C.L. Elmore, V.A. Gibeault and J.S.Reints. 1997. Common bermudagrass (Cynodondactylon) management in cool-season grasses.Weed Technology 11:478-483.4. Hassan, G., G. Mueller-Warrant and S. Griffith. 2002.Differential sensitivity of Italian ryegrass (Loliummultiflorum) cultivars to fenoxaprop. Weed Science50:567-575.5. Johnson, B.J. 1995. Tolerance of four seeded commonbermudagrass (Cynodon dactylon) types to herbicides.Weed Technology 9:794-800.6. Johnson, B.J., and R.R. Duncan. 2001. Effects of herbicidetreatments on suppression of seashore paspalum(Paspalum vaginatum) in bermudagrass(Cynodon spp.). Weed Technology 15:163-169.7. McCalla, Jr., J.H., M.D. Richardson, D.E. Karcher andJ.W. Boyd. 2004. Tolerance of seedling bermudagrassto postemergence herbicides. Crop Science44:1330-1336.8. McElroy, J.S., F.H. Yelverton and L.S. Warren, Jr.2004. Control of green and false-green kyllinga(Kyllinga brevifolia and K. gracillima) at golf coursefairway and rough mowing heights. WeedTechnology (In review).9. National Turfgrass Evaluation Program. 2004.http://www.ntep.org (confirmed Oct. 15, 2004).➤ Yukon is generally more sensitive to herbicides than Princess 77, Riviera andSavannah.➤ AAtrex and Confront should not be applied during establishment of any seededbermudagrass cultivar. Injury from Confront is primarily attributed to triclopyr.➤ Herbicides generally used for broadleaf weed control such as 2,4-D, dicamba,mecoprop, clopyralid and triclopyr should be used with caution during seeded bermudagrassestablishment.➤ Drive, Monument and MSMA are generally safe for all cultivars, but some delay ingrow-in may occur.➤ When applied after initial stolon development, Revolver did not injure or delay grow-inof any cultivar during seeded establishment.J. Scott McElroy, Ph.D. (mcelroy@utk.edu), is an assistantprofessor and Greg K. Breeden, M.S., is an extensionassistant in the plant science department, University ofTennessee, Knoxville. Fred H. Yelverton, Ph.D., is a professorand Travis W. Gannon, M.S., is a research associatein the crop sciences department, North Carolina StateUniversity, Raleigh. Shawn D. Askew, Ph.D., is an assistantprofessor in the department of plant pathology, physiologyand weed science, Virginia Polytechnic and StateUniversity, Blacksburg. Jeffery F. Derr, Ph.D., is a professorin the department of plant pathology, physiology andweed science, Virginia Polytechnic and State University,Hampton Roads Agricultural Research and ExtensionCenter, Virginia Beach.158 GCMJanuary 2005