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/448298
Field Science 14 SportsTurf | February 2015 www.sportsturfonline.com safety of these herbicides between cool- and warm-season grasses. Pay particular attention to the herbicide label regard- ing use on more sensitive species like the fine fescues and hybrid bermudagrasses, as well. Never use a preemergence or postemergence herbicide for crabgrass or other annual grassy weed control before fully reading and understanding the use requirements and restrictions on the label. A good example would be Dimension (dithiopyr) that cannot be safely applied at the time of seeding or until the desirable turfgrass has been mowed at least 2-3 times. Also, there is a suggested waiting period or time interval after a Dimension application of 6 to 16 weeks before seeding/overseeding depending on applica- tion rate. Thus the standard "offensive" strategy becomes a problem in attempting to control crabgrass and other weed species during turfgrass establishment in seeding or overseeding operations. One approach is "site specific" management by only applying a preemergence herbicide on sports field areas that DO NOT require seeding or overseeding like outside the hash marks, beyond the 20 or 30 yard lines, end zone areas, and side line areas on football fields. Where seeding or overseeding is necessary, there are a few options. Herbicide options that are considered to be safe for use at the time of seeding or at 4 weeks after seedling emergence are listed in. The list is restricted to only a few but includes siduron (Tupersan), mesotrione (Tenacity) and Pylex (topramazone). Follow the label carefully. When used properly, siduron will reduce crabgrass, goosegrass, foxtail and many summer annual broadleaf weeds by 70-80%. Mesotrione (Tenacity) and Pylex (topramezone) are excellent preemergence tools to use in seedings for reducing spring/summer weed pressure from crabgrass, goosegrass, sedges, and summer annual broadleaf weeds by 90% or greater. These two latter products allow sports turf managers to be more successful with spring and summer seedings by effectively reducing weed competition and actually "widening the window" for successful seeding/overseeding into the summer. Both Tenacity and Pylex are in the same chemical fam- ily and inhibit carotenoid biosynthesis with chlorophyll destruction resulting in all susceptible weeds turning white (bleaching symptom). These two herbicides have both pre- and postemergence activity on crabgrass and many other weeds. Preemergence residual with both these herbicides, how- ever, lasts only about 30 days and, therefore, will not provide season-long preemergence activity. Where longer preemer- gence activity/residual is required, like in early spring or early summer seedings/overseedings, a sequential or follow-up application can be made at a 30-day interval or at least 4 weeks after seedling emergence. Where perennial ryegrass is a principle component of the sports field turf, it is NOT sug- gested that the interval on repeat applications be shortened to less than 30 days. Reducing crabgrass and other annual weed competition during seeding operations with these latter two herbicides should greatly enhance your success at spring and summer seedings/overseedings. They are a definite benefit in establishment programs should be included in every sports turf manager's weed control tool box. Defensive strategies Postemergence herbicide options or "defensive" strategies for controlling crabgrass in established turfgrasses include Acclaim Extra (fenoxaprop p-ethyl), a number of quinclorac (Drive DF) products and XLR8, Tenacity (mesotrione), Pylex (topramezone) and a few combination pre/post products including Calvalcade PQ (combo of prodiamine plus quinclo- rac), Echelon (combo of sulfentrazone plus prodiamine), and Dimension (dithiopyr). Dimension has early postemergence activity on crabgrass so young (3-5 leaf and before tillering) crabgrass is controlled and a preemergence barrier is set in place for the remainder of the season. This is a great herbicide tool in the spring where crabgrass germination has occurred before the application of a preemergence herbicide. A similar "defensive" strategy is the basis for the combination products Calvalcade PQ and Echelon where the quinclorac or sulfentra- zone provides post activity on already germinated crabgrass and the prodiamine provides a preemergence barrier for the remainder of the season. Drive DF products and XLR8 are good "defensive" options where crabgrass has matured beyond the early post crab- grass stage (tillered). It is a foliar absorbed post herbicide that requires a surfactant and needs to be applied at no less than 0.75 lbs. ai/A for best results. XLR8 would be an excellent choice for sports turf managers in late summer where a rescue treatment for quick crabgrass knockdown is required before the beginning of the playing season (a "defensive" save face strategy). XLR8 will discolor and reduce the visibility of crab- grass in the canopy within 3-5 days in conjunction with a good fertility program. Finally, both Tenacity and Pylex have been evaluated for postemergence crabgrass control in Ohio State research over the past several years. Both again are so called "bleacher" her- bicides. Two sequential applications of both herbicides will effectively control mature crabgrass on a consistent basis. The addition of triclopyr with Tenacity (8 oz product/A) increases the efficacy of Tenacity to where a single application of the combo provides good to excellent post crabgrass control. Pylex alone has shown good to excellent postemergence activity on tillered crabgrass in a single application. The inclusion of tric- lopyr with Pylex also enhances its activity on tillered crabgrass and many other weeds. Pylex is a stellar product for goosegrass control. The inclusion of triclopyr in combos with Tenacity or Pylex also eliminates the bleaching or whitening symptom. ■ ST Dr. John R. Street is an extension/research associate professor; Dr. David Gardner is a research/teaching associate professor; and Pamela Sherratt is a senior extension sports turf specialist, all with the Department of Horticulture and Crop Science at The Ohio State University, Columbus.