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: http://read.dmtmag.com/i/369217
14 SportsTurf | September 2014 www.sportsturfonline.com Field Science to injury to desirable turf. Additionally, applications in spring must be made before air temperatures reach 85°F. Moreover, applications to Kentucky bluegrass must be delayed a minimum of 12 months after seeding. Research trials have shown some benefit to tank mixing Tenacity and Xonerate for annual bluegrass control in cool-season turfgrass; however, more information is needed before this mixture becomes a labeled option that athletic field managers can legally apply to their turf. At the current time, the best use of Xonerate on athletic field turf is for annual bluegrass control on warm-season fields overseeded with perennial ryegrass for spring football and baseball. Pylex (active ingredient is topramezone) is a new herbicide for use in turfgrass that is also safe for use on many cool-season turf- grasses including Kentucky bluegrass, perennial ryegrass, and tall fescue (Festuca arundinacea). Pylex works similar to Tenacity in that it inhibits carotenoid production, turning susceptible weeds white after application. Pylex is an option for postemergence weed con- trol in established turf and can also be used when establishing new cool-season turfgrass stands from seed. However, applications after seeding should be delayed a minimum of 4 weeks. Although Pylex hasno activity on annual bluegrass, it can be used to select winter annual broadleaf weeds such as common chickweed, speedwell spe- cies, Shepherd's-purse, hairy bittercress, and henbit. Drive XLR8 (active ingredient is quinclorac) is often thought of as an herbicide for postemergence crabgrass control. Many ath- letic field managers are unaware that Drive XLR8 controls a wide spectrum of broadleaf weeds including many winter annual species. Drive XLR8 is also safe for use during the establishment of cool- season species used on athletic fields. Applications to newly seeded Kentucky bluegrass can be made 4 weeks after seeding; on peren- nial ryegrass, Drive XLR8 can be applied at seeding and 4 weeks thereafter as well. Athletic field managers should be advised that many products containing quinclorac are available under different trade names. Always check the product label to determine if a particular herbicide can be applied to newly established turf. For example, SquareOne Herbicide (active ingredients are quinclorac + carfentrazone) can be applied to Kentucky bluegrass and perennial ryegrass 7 days after emergence. Comparatively, applications of Q4-Plus (active ingre- dients are quinclorac + sulfentrazone + 2,4-D + dicamba) must be delayed until at least 28 days after emergence. Warm-season athletic fields Winter annual weed management is a critical issue on warm- season athletic fields. As temperatures cool throughout fall and winter, warm-season turfgrasses grow less aggressively and often enter dormancy in many locations. This renders warm-season athletic fields non-competitive against winter annual weed invasion. There are several factors that make winter annual weed manage- ment on warm-season athletic fields complicated including decisions regarding overseeding and managing the evolution of herbicide resistant weeds. Overseeded Fields. Many warm-season athletic field managers chose to overseed fields with cool-season species such as perennial ryegrass during fall. This practice ensures that fields will remain green throughout the winter and early spring, which can be important for sports like baseball that often begin early in the calendar throughout much of the southern United States. It also serves to protect dormant bermudagrass crowns from the negative effects of foot traffic during dormancy. However, inputs of irrigation water and fertilizer nutri- ents required to establish a successful stand of overseeded turf on warm-season athletic fields can encourage invasion of winter annual weeds, particularly annual bluegrass. Much like controlling the win- ter annual weeds; overseeded perennial ryegrass must be removed in the spring for warm-season turfgrasses to recuperate. One option for annual bluegrass management in these scenarios is to apply a preemergence herbicide like Barricade (active ingredient is prodiamine) 8 to 10 weeks before overseeding. However, in most climates annual bluegrass pressure will likely be quite low during this 8 to 10 week period before fall overseeding. Additionally, this practice may not provide complete control in most environments because multiple flushes of annual bluegrass germination can occur throughout the fall. Another option is to apply an acetolactate synthase (ALS) inhibit- ing herbicide such as Revolver (active ingredient is foramsulfuron), Monument (active ingredient is trifloxysulfuron), or Katana (active ingredient is flazasulfuron) closer to overseeding. These herbicides can safely be applied 7 to 28 days before overseeding species such as perennial ryegrass into bermudagrass athletic fields. Be advised that re-seeding intervals vary by product and field managers should con- sult the herbicide label for more specific information. Applications of ALS inhibiting herbicides will control any annual bluegrass plants that may have emerged before overseeding and provide some residual control of those germinating thereafter. Some field managers chose to follow-up these applications with postemergence treatments after overseeding. As previously men- tioned, Xonerate is a new herbicide that fits this use pattern. Prograss (active ingredient is ethofumesate) is labeled for postemergence annual bluegrass control in overseeded perennial ryegrass turf on Figure 4. Many warm-season athletic fields are not overseeded during the winter and enter full dormancy.