SportsTurf provides current, practical and technical content on issues relevant to sports turf managers, including facilities managers. Most readers are athletic field managers from the professional level through parks and recreation, universities.
Issue link: https://read.dmtmag.com/i/162108
FieldScience enter a period of dormancy during winter where growth ceases. Non-selective herbicides such as glyphosate (e.g., Roundup, etc.) that normally would be injurious to turfgrass can be used to control weeds during this dormancy period (Anonymous 2010). Many athletic field managers in the transition zone apply glyphosate for weed control during bermudagrass dormancy. Glyphosate applications to dormant bermudagrass fields often provide effective and more economical broad-spectrum weed control during winter conditions than other materials, particularly inhibitors of acetolactate synthase (ALS) such as foramsulfuron (e.g., Revolver), trifloxysulfuron (e.g., Monument), and flazasulfuron (e.g., Katana). As a result, many weed populations on bermudagrass athletic fields are under intense glyphosate selection pressure, similar to that which has been reported following the advent of glyphosate-tolerant crops in agricultural production systems. Recently two biotypes of annual bluegrass with resistance to glyphosate have been reported in Missouri and Tennessee (Binkholder et al. 2011; Brosnan et al. 2012). In both cases, repeated applications of glyphosate were used to control annual weeds during periods of winter dormancy for over 10 consecutive years. RESISTANCE TO OTHER HERBICIDES Resistance is an issue with herbicides other than glyphosate. ALS-inhibiting herbicides such as foramsulfuron (e.g., Revolver), trifloxysulfuron (e.g., Monument), and flazasulfuron (e.g., Katana) are commonly used on warmseason athletic fields to remove overseeded perennial ryegrass (Lolium perenne) and control other problematic grassy weeds such as annual bluegrass and goosegrass. Repeated use of these herbicides for annual bluegrass control has led to the development of annual bluegrass biotypes with resistance to ALS inhibiting herbicides. Cross et al. (2013) identified multiple biotypes of annual bluegrass in the southeastern United States resistant to foramsulfuron and trifloxysulfuron. Populations of annual bluegrass in Tennessee have recently been identified that are tolerant to 8x label rate applications of foramsulfuron and trifloxysulfuron. Photosystem II (PSII)-inhibiting herbicides such as simazine (i.e., Princep) and amicarbazone (i.e., Xonerate) are used for annual bluegrass control in warm-season turf. Repeated use of these materials, particularly simazine, has led to populations of annual 10 SportsTurf | September 2013 bluegrass resistant to PSII-inhibiting herbicides in Alabama, Mississippi, North Carolina, Oregon, and Virginia (Heap 2013). Hutto et al. (2004) documented the presence of simazineresistant annual bluegrass on 43% of the golf courses in Mississippi. Dinitroaniline (DNA) herbicides such as pendimethalin (e.g., Pendulum) and prodiamine (e.g., Barricade) are regularly used for preemergence control of grassy weeds such as crabgrass, annual bluegrass, and goosegrass. Multiple biotypes of annual bluegrass and goosegrass resistant to the DNA herbicide prodiamine have been reported in the southeastern United States as the result of repeated use of prodiamine (Cutulle et al. 2009; Isgrigg et al. 2002; Lowe et al. 2001; McCullough et al. 2013; Mudge et al. 1984). WHY ANNUAL BLUEGRASS (POA ANNUA)? To date, the majority of instances of herbicide resistance in turf have occurred in annual bluegrass. The reason for this phenomenon is not completely understood; however, herbicide resistance is most common in annual species (Heap 2013). Prolific annual bluegrass seed production may result in more rapid and effective dispersion and survival of herbicide resistant plants (McElroy et al. 2004). In agricultural production systems, many weed species developing herbicide resistance, such as Palmer amaranth (Amaranthus palmeri) and horseweed (Conzya canadensis), produce copious amounts of seed as well (Nandula et al. 2006; Norsworthy et al. 2008). WHAT CAN BE DONE? In order to prevent herbicide resistance from becoming a problematic issue on athletic fields, turf managers must change their approach to weed control. The first step is to learn the manner in which different herbicides work to control weeds. Be sure to consult with local University Extension offices for more information on this important topic. Acquiring this knowledge will not only improve the professionalism of athletic field managers in general but it is also critical for developing weed control programs to prevent resistance development on warm- and cool-season athletic fields. Applying a rotation of different herbicides targeting varying sites of action (i.e., using products that work differently) will reduce selection pressure for herbicide-resistant weeds. However, it is critical that field managers rely on more than just herbicide applications to con- trol weeds. Diversified weed management programs involving sound agronomic practices, integrated pest management strategies, and herbicide applications will ensure that herbicide resistance does not become a problem of athletic field turf in the future. n Literature Cited Anonymous. 2010. Roundup ProMax herbicide label. Monsanto Company. St. Louis, MO. USA pp 1-11. Binkholder, K. M., B. S. Fresenburg, T. C. Teuton, X. Xiong, & R. J. Smeda. 2011. Selection of glyphosate resistant annual bluegrass (Poa annua L.) on a golf course. Weed Sci. 59:286-289. Brosnan, J.T., G.K. Breeden, & T.C. Mueller. 2012a. A glyphosate-resistant biotype of annual bluegrass in Tennessee. Weed Sci. 60:97-100. Cross, R.B., L.B. McCarty, N. Tharayil, T. Whitwell, & W.C. Bridges Jr. 2013. Detecting annual bluegrass resistance to ALS-inhibiting herbicides using a rapid diagnostic assay. Weed Sci. 61: 384-389. Cutulle, M.A., J.S. McElroy, R.W. Millwood, J.C. Sorochan, & C.N. Stewart Jr. 2009. Selection of bioassay method influences detection of annual bluegrass resistance to mitotic-inhibiting herbicides. Crop Sci. 49:1088-1095. Heap, I. 2013. International survey of herbicide resistant weeds. http://www.weedscience.org. Accessed: 20 March 2013. Hutto, K.C., G.E. Coats, & J.M. Taylor. 2004. Annual bluegrass (Poa annua) resistance to simazine in Mississippi. Weed Technol. 18:846–849. Isgrigg, J., III, F.H. Yelverton, C. Brownie, & L.S. Warren, Jr. 2002. Dinitroaniline resistant annual bluegrass in North Carolina. Weed Sci. 50:86–90. Lowe, D.B., G.A. Swire-Clark, L.B. McCarty, T. Whitwell, & W.V. Baird. 2001. Biology and molecular analysis of dinitroaniline-resistant Poa annua L. Int. Turf. Soc. Res. J. 9:1019-1025. McCullough, P.E., J. Yu, D. Gomez de Barreda. 2013. Efficacy of preemergence herbicides for controlling dinitroaniline resistant goosegrass in Georgia. Weed Technol. (in press) McElroy, J.S., R.H. Walker, G.R. Wehtje, & E. van Santen. 2004. Annual bluegrass (Poa annua) populations exhibit variation in germination response to temperature, photoperiod, and fenarimol. Weed Sci. 52:47-52. Mudge, L.C., B.J. Gossett, & T.R. Murphy. 1984. Resistance of goosegrass (Eleusine indica) to dinitroaniline herbicides. Weed Sci. 32:591–594. Nandula, V.K., T.W. Eubank, D.H. Poston, C.H. Koger, & K.N. Reddy. 2006. Factors affecting germination of horseweed (Conzya canadensis). Weed Sci. 54:898-902. Norsworthy, J.K., G.M. Griffith, R.C. Scott, K.L. Smith, & L.R. Oliver. 2008. Confirmation and control of glyphosate-resistant Palmer amaranth (Amaranthus palmeri) in Arkansas. Weed Technol. 22:108-113. Vencill, W.K., R.L. Nichols, T.M. Webster, J.K. Soteres, C. Mallory-Smith, N.R. Burgos, W.G. Johnson, & M.R. McClelland. 2012. Herbicide resistance: toward an understanding of resistance development and the impact of herbicide-resistant crops. Weed Sci. 60(sp1):2-30. www.sportsturfonline.com