Bermudagrass golf course fairways and athletic fields are commonly overseeded with a cool-season turfgrass, like perennial ryegrass, to provide green cover and improve aesthetic quality during winter months (Horgan and Yelverton, 2001). Thoms et al. (2011) reported that overseeding ‘Tifway 419’ hybrid bermudagrass (Cynodon dactylon × C. transvaalensis) not only increased green cover under simulated traffic, but hypothesized that overseeding protected dormant bermudagrass from traffic stress. Fall overseeding is a common practice on golf courses and athletic fields in the southern United States. Perennial ryegrass may persist in bermudagrass turf for three to nine months depending on geographic location (Mazur, 1984).
Applications of preemergence (PRE) herbicides for summer annual weed control can compromise establishment of overseeded cool-season turfgrass species in the fall. Yelverton and McCarty (2001) reported that prodiamine reduced perennial ryegrass establishment when applied at 430 g·ha−1 6 weeks before overseeding. The researchers also demonstrated that increasing the prodiamine rate to 560 g·ha−1 extended the interval required for successful perennial ryegrass establishment to 8 weeks. Similarly, Keeley and Zhou (2005) reported that prodiamine at 840 g·ha−1 reduced kentucky bluegrass (Poa pratensis) establishment unless broadcast seeding was delayed for 14 weeks after herbicide treatment. This interval increased to 16 weeks when seeding was performed with slit-seeding techniques often used for overseeding bermudagrass turf.
Indaziflam is an alkylazine herbicide that controls winter and summer annual weeds in bermudagrass turf by inhibiting cellulose biosynthesis (Myers et al., 2009). Brosnan et al. (2011) reported that PRE applications of indaziflam at 35 to 70 g·ha−1 controlled smooth crabgrass (Digitaria ischaemum) similar to prodiamine at 840 g·ha−1. Further studies illustrated that indaziflam provides effective postemergence control of nontillering smooth crabgrass plants at 35 g·ha−1 (Brosnan and Breeden, 2012). Current labeling restricts perennial ryegrass overseeding following indaziflam applications. Perennial ryegrass overseeding must be delayed a minimum of eight months following treatment at 35 g·ha−1 and 12 months at rates greater than 53 g·ha−1. Overseeding restrictions of this nature may limit indaziflam use by turf managers.
Sequential application programs could provide turf managers with effective summer annual weed control without compromising perennial ryegrass establishment. Perry et al. (2011) reported that indaziflam (20 to 60 g·ha−1) programs involving fall (October and November) and spring (March and April) applications controlled large crabgrass (Digitaria sanguinalis) >90% in June. These regimes may allow for successful establishment of overseeded perennial ryegrass in late fall. However, Perry et al. (2011) did not evaluate perennial ryegrass establishment.
Data describing effects of single and sequential indaziflam applications on overseeded perennial ryegrass establishment and summer annual weed control are limited. Considering the prevalence of dinitroaniline-resistant annual grassy weeds in the southern United States (Cutulle et al., 2009; Isgrigg III et al., 2002; Mudge et al., 1984; Vaughn et al., 1990), providing turf managers with a new mode of action may be beneficial for resistance management. Therefore, the objectives of this research were to evaluate the effects of indaziflam applications on perennial ryegrass establishment and summer annual weed control.
Ahrens, W.H., Cox, D.J. & Budhwar, G. 1990 Use of the arcsine and square root transformations for subjectively determined percentage data Weed Sci. 38 452 458
Brosnan, J.T. & Breeden, G.K. 2012 Application placement affects postemergence smooth crabgrass and annual bluegrass control with indaziflam Weed Technol. (In press)
Brosnan, J.T., Breeden, G.K., McCullough, P.E. & Henry, G.M. 2012 Pre- and postemergence annual bluegrass control with indaziflam Weed Technol. 26 48 53
Brosnan, J.T., McCullough, P.E. & Breeden, G.K. 2011 Smooth crabgrass control with indaziflam at various spring timings Weed Technol. 25 363 366
Cutulle, M.A., McElroy, J.S., Millwood, R.W., Sorochan, J.C. & Stewart, C.N. 2009 Selection of bioassay method influences detection of annual bluegrass resistance to mitotic-inhibiting herbicides Crop Sci. 49 1088 1095
Dawson, B. 2011 A drought for the centuries: It hasn’t been this dry in Texas since 1789. 19 Dec. 2011. <http://texasclimatenews.org/wp/?p=3355>
Horgan, B.P. & Yelverton, F.H. 2001 Removal of perennial ryegrass from overseeded bermudagrass using cultural methods Crop Sci. 41 118 126
Isgrigg, J. III, Yelverton, F.H., Brownie, C. & Warren, L.S. 2002 Dinitroaniline resistant annual bluegrass in North Carolina Weed Sci. 50 86 90
Keeley, S.J. & Zhou, H. 2005 Preemergence herbicide and seeding methods effects on seedling growth of kentucky bluegrass Weed Technol. 19 43 46
Mudge, L.C., Gossett, B.J. & Murphy, T.R. 1984 Resistance of goosegrass (Eleusine indica) to dinitroaniline herbicides Weed Sci. 32 591 594
Myers, D.F., Hanrahan, R., Michel, J., Monke, B., Mudge, L., Olsen, C., Parker, A., Smith, J. & Spak, D. 2009 Indaziflam/BCS AA170717: A new herbicide for preemergent control of grasses and broadleaves in turf and ornamentals Proc. Southern Weed. Sci. Soc. 62 393
Perry, D.H., McElroy, J.S., Doroh, M.C. & Walker, R.H. 2011 Indaziflam utilization for controlling problematic turfgrass weeds. Online. Appl. Turfgrass Sci. doi:10.1094/ATS-2011-0428-01-RS
Thoms, A.W., Sorochan, J.C., Brosnan, J.T. & Samples, T.J. 2011 Perennial ryegrass (Lolium perenne L.) and grooming affect bermudagrass traffic tolerance Crop Sci. 51 2204 2211
Vaughn, K.C., Vaughn, M.A. & Gossett, B.J. 1990 A biotype of goosegrass (Eleusine indica) with an intermediate level of dinitroaniline herbicide resistance Weed Technol. 4 157 162
Yelverton, F.H. & McCarty, L.B. 2001 Tolerance of perennial ryegrass and Poa annua control with herbicides in overseeded bermudagrass Intl. Turfgrass Soc. Res. J. 9 1050 1055