A New Herbicide for Poa Annua Control in Turf
Tom Reed, Graduate Assistant
Patrick McCullough, Assistant Professor
University of Georgia
Poa annua (annual bluegrass) is a problem winter annual weed in turf. Annual bluegrass has a bunch-type growth habit, light green color, and abundant seedhead production. Since Poa annua has poor stress tolerance, decline of populations in late spring reduces turf quality and may predispose areas to infestations of summer annual weeds, such as crabgrass (Beard 1970; Lush 1989).
Postemergence herbicides are used in late winter or spring to control Poa annua,but populations resistant to specific chemistries may limit potential for successful control. Herbicide resistance in annual bluegrass populations may result from repeated use of the same herbicide or mode of action in consecutive years.
- Products like flazasulfuron (Katana), foramsulfuron (Revolver), and trifloxysulfuron (Monument) are popular sulfonylureas used for postemergence annual bluegrass control in warm-season turfgrasses but significant resistance issues have been reported in turf and other crops (McElroy et al. 2013).
- Extensive use of triazines (atrazine and simazine) has led to prevalent annual bluegrass resistance in turfgrass in Georgia and other states.
- Glyphosate is used for controlling annual bluegrass in dormant bermudagrass, but overuse has also resulted in the spread of resistant populations throughout the southern U.S.
Turfgrass managers can reduce the chance of resistance by using herbicides with different modes of action in Poa annua control programs.
Flumioxazin is the active ingredient in SureGuard, a product labeled in 2011 for use in dormant bermudagrass. Flumioxazin has been extensively used in ornamentals and row crops including cotton and peanuts for annual weed control. Flumioxazin is a chlorophyll synthesis inhibitor similar to carfentrazone, oxadiazon, and sulfentrazone. In susceptible plants these herbicides inhibit the enzyme protoporphyrinogen oxidase (Protox). The inhibition of Protox leads to a toxic accumulation of compounds that destroy membranes and cause irreversible damage to plant cells. Protox inhibitors are not systemic herbicides, but are mainly used for annual weed control.
Unlike other Protox inhibitors, flumioxazin provides postemergence annual bluegrass control in dormant bermudagrass. In Georgia, flumioxazin applications are generally most effective in November and December, prior to annual bluegrass tillering. Applications at spring timings may also control Poa annua with residual control for summer annual weeds, including crabgrass and goosegrass (McCullough et al. 2012).
Currently, flumioxazin use is limited to dormant bermudagrass since applications may cause injury to actively growing turf (Umeda 2012). Preliminary experiments at the University of Georgia show flumioxazin efficacy increases when temperatures are warmer in spring compared to winter timings. Flumioxazin also appears to be root absorbed and irrigation could maximize efficacy of applications. Our current research at the University of Georgia is evaluating the effectiveness of flumioxazin with adjuvants and tank-mixtures with other herbicides on mature annual bluegrass. We are also evaluating residual control of crabgrass and goosegrass following applications for postemergence annual bluegrass control and tolerance of five warm-season turfgrasses.
Overall, flumioxazin has potential as a new tool for annual bluegrass control especially if resistance is suspected in populations. Flumioxazin may provide a new mode of action for postemergence annual bluegrass control in turf, but end-users must understand that applications are limited to dormant bermudagrass at this time and there are limitations on efficacy during winter months. For best results, read and follow label directions before use of any herbicide.
Beard, J. B. 1970. An ecological study of annual bluegrass. USGA Green Sect. Rec. 8:13
Lush, W. M. 1989. Adaptation and differentiation of golf course populations of annual bluegrass. Weed Sci. 37:54-59.
McElroy J. S., M. L. Flessner, Z. Wang, F. Dane, R. H. Walker, and G. R. Wehtje. 2013. A Trp574 to Leu amino acid substitution in the ALS gene of annual bluegrass (Poa annua) is associated with resistance to ALS-inhibiting herbicides. Weed Sci. 61(1):21-25.
McCullough, P., B. Nutt, and J. Chamberlin. 2012. Flumioxazin efficacy for controlling annual bluegrass and smooth crabgrass. Proc. South Weed Sci. Soc. 199.
Umeda, K. 2012. Utility of flumioxazin and indaziflam for Poa annua control in non-overseeded bermudagrass turf. Proc. Weed Sci. Soc
Please share this information with others in the landscape & turf industry. For more information:
Call your local Extension Agent at (800) ASK-UGA1 or locate your local Extension Office at http://www.caes.uga.edu/extension/statewide.cfm
For more Landscape Alerts please visit the Georgia Center for Urban Agriculture