CBG is a problematic weed in lawns, parks, and golf course roughs in much of the northern United States. This perennial weed can spread quickly as a result of its stoloniferous growth habit. A desirable grass at mowing heights less than 1.5 cm, CBG is usually considered a weed in turfgrass maintained at 2 cm or higher, because it becomes puffy and unattractive (Branham et al., 2005). Nonselective herbicides such as glyphosate can be used for CBG control, but a single application does not always provide commercially acceptable control (Askew et al., 2004). Nonselective herbicides also cause unsightly bare patches after application, and reseeding desirable turfgrass is required. Triclopyr ester can suppress CBG selectively, but it is less effective than mesotrione and can cause tall fescue (Festuca arundinacea Schreb.) injury at rates required for suppression (Dernoeden et al., 2008).
Mesotrione is a p-hydroxyphenylpyruvate dioxygenase (HPPD) inhibiting herbicide first registered in 2008 for use on most cool-season turfgrass species at single and annual application rates up to 280 g·ha–1 and 560 g·ha–1, respectively (Anonymous, 2011; Mitchell et al., 2001). Mesotrione can control or suppress CBG in perennial ryegrass (Lolium perenne L.), kentucky bluegrass (Poa pratensis L.), and tall fescue. Research demonstrated consistently that sequential mesotrione applications provide more CBG control than single applications (Branham et al., 2005; Dernoeden et al., 2008; Jones and Christians, 2007; Xie et al., 2011). Jones and Christians (2007) demonstrated that 2week mesotrione reapplication intervals provided more CBG control than 6-week intervals. Branham et al. (2005) found that CBG control with mesotrione was inconsistent. In their research, mesotrione applied twice at 280 g·ha–1 at a 3-week interval in late spring provided 13% and 97% control in 2003 and 2004, respectively, at 3 months after initial treatment (MAIT). The cause of this year-to-year variability was not clear, although three sequential applications of 420 g mesotrione/ha (more than registered use rates) provided more consistent control. The number of sequential applications did not affect CBG control in Maryland and Connecticut as two, three, or four sequential applications of mesotrione at 140 or 210 g·ha–1 provided similar (>90%) CBG control at 3 to 4 MAIT (Dernoeden et al., 2008). Using lower mesotrione rates than other researchers, Xie et al. (2011) demonstrated that tank mixing mesotrione with urea ammonium nitrate (UAN) improved CBG control provided by three sequential applications of mesotrione at 56 or 70 g·ha–1. Three sequential applications of mesotrione + UAN at 70 g·ha–1 provided 97% or more CBG control from late-summer applications compared with less than 80% control without UAN. Although most researchers evaluated spring or summer applications, Beam et al. (2006) evaluated fall applications and observed more than 90% control from two sequential applications of mesotrione at 280, 170, and 60 g·ha–1.
The efficacy of mesotrione-based tank mixtures for CBG control has not been investigated. Dernoeden et al. (2008) found that triclopyr ester alone provided CBG suppression but did not examine tank mixtures of mesotrione + triclopyr ester. Tank mixtures of triclopyr ester and HPPD-inhibiting herbicides can reduce bleaching symptoms and improve common bermudagrass (Cynodon dactylon L.) and smooth crabgrass [Digitaria ischaemum (Schreb) Schreb ex Muhl.] control (Brosnan and Breeden, 2013; Yu and McCullough, 2016).
Amicarbazone is a photosystem II (PSII)-inhibiting herbicide registered for annual bluegrass (Poa annua L.) control in kentucky bluegrass and CBG at up to 100 g·ha–1 and 50 g·ha–1 per application, respectively (Anonymous, 2012; Dayan et al., 2009). Amicarbazone can cause transient sublethal injury to both CBG and kentucky bluegrass at 100 g·ha–1 (McCullough et al., 2010). Given that synergy between sublethal rates of other PSII-inhibiting herbicides and HPPD-inhibiting herbicides has been demonstrated previously, investigating tank mixtures of mesotrione and amicarbazone for creeping bentgrass control is warranted (Woodyard et al., 2009).
Research investigating herbicides for tough-to-control perennial weeds such as dallisgrass (Paspalum dilatatum L.) and common bermudagrass often evaluates treatment responses for several months or more after the last herbicide application to assess regrowth from perennial structures (Brosnan and Breeden, 2013; Henry et al., 2007). However, with the exception of Jones and Christians (2007) and Xie et al. (2011), previous CBG control research evaluated efficacy for only 2 to 4 months after the final application (Beam et al., 2006; Branham et al., 2005; Dernoeden et al., 2008). Furthermore, we are not aware of research investigating multiyear sequential application programs. Our communications with practitioners suggest CBG recovers from single-year sequential mesotrione application regimens and that evaluating the efficacy of 2-year regimens is warranted.
The objective of this research was to evaluate 2-year sequential application regimens of mesotrione alone and in tank mixes with triclopyr ester or amicarbazone.
Anonymous. 2011 Tenacity herbicide label. Syngenta Crop Protection, Inc., Greensboro, NC
Anonymous. 2012 Xonerate herbicide label. Arysta LifeScience, Cary, NC
Askew, S.D., Beam, J.B. & Reigo, D.C. 2004 Alternatives to glyphosate for creeping bentgrass control Proc. Northeastern Weed Sci. Soc. 58 115 (abstr.)
Beam, J.B., Barker, W.L. & Askew, S.D. 2006 Selective creeping bentgrass (Agrostis stolonifera) control in cool-season turfgrass Weed Technol. 20 340 344
Branham, B.E., Sharp, W., Kohler, E.A., Fermanian, T.W. & Voigt, T.B. 2005 Selective control of creeping bentgrass (Agrostis stolonifera L.) in Kentucky bluegrass (Poa pratensis L.) turf Intl. Turfgrass Soc. Res. J. 10 1164 1169
Brewer, J.R., Willis, J., Rana, S.S. & Askew, S.D. 2017 Response of six turfgrass species and four weeds to three HPPD-inhibiting herbicides Agron. J. 109 1777 1784
Dernoeden, P.H., Kaminski, J.E. & Fu, J. 2008 Selective creeping bentgrass control in Kentucky bluegrass and tall fescue with mesotrione and triclopyr ester HortScience 43 509 513
Henry, G.M., Yelverton, F.H. & Burton, M.G. 2007 Dallisgrass (Paspalum dilatatum) control with foramsulfuron in bermudagrass turf Weed Technol. 21 759 762
Jones, M.A. & Christians, N.E. 2007 Mesotrione controls creeping bentgrass (Agrostis stolonifera) in Kentucky bluegrass Weed Technol. 21 402 405
McCullough, P.E., Hart, S.E., Weisenberger, D. & Reicher, Z.J. 2010 Amicarbazone efficacy on annual bluegrass and safety on cool-season turfgrass Weed Technol. 24 461 470
Mitchell, G., Bartlett, D.W., Fraser, T.E.M., Hawkes, T.R., Holt, D.C., Townson, J.K. & Wichert, R.A. 2001 Mesotrione: A new selective herbicide for use in maize Pest Mgt. Sci. 57 120 128
Reicher, Z.J., Weisenberger, D.V., Morton, D.E., Branham, B.E. & Sharp, W. 2011 Fall applications of mesotrione for annual bluegrass control in Kentucky bluegrass Appl. Turfgrass Sci., doi: 10.1094/ATS-2011-0325-01-RS.
Skelton, J.J., Sharp, W. & Branham, B.E. 2012 Postemergence control of annual bluegrass with mesotrione in Kentucky bluegrass HortScience 47 522 526
Woodyard, A.J., Hugie, J.A. & Riechers, D.E. 2009 Interactions of mesotrione and atrazine in two weed species with different mechanisms for atrazine resistance Weed Sci. 57 369 378
Xie, L., Li, D., Fang, W. & Howatt, K. 2011 Urea ammonium nitrate additive and raking improved mesotrione efficacy on creeping bentgrass HortTechnology 21 41 45
Yu, J. & McCullough, P.E. 2016 Triclopyr reduces foliar bleaching from mesotrione and enhances efficacy for smooth crabgrass control by altering uptake and translocation Weed Technol. 30 516 523