Tennessee Turfgrass – Devon Carroll and Jim Brosnan, Ph.D.
A new season often brings new technology to the turfgrass industry and 2020 is no exception. Six new herbicides are available to turfgrass managers in 2020 including Coastal, Cheetah Pro, Crew, GameOn, Manuscript, and Vexis. These products contain active ingredients from seven mode-of-action groups with several combined in pre-packaged mixtures. A mode-of-action group indicates the physiological mechanism a herbicide uses to control weeds and can be easily identified on product labeling using the Weed Science Society of America (WSSA) group numbering system [e.g., dithiopyr (the active ingredient in Dimension) belongs to WSSA Group 3].
These new herbicides have been researched for several years at land-grant universities, such as the University of Tennessee, to determine how they can be optimally used to control weeds of cool- and warm-season turfgrass while minimizing environmental impact. This article will outline attributes of these new herbicides to aid turfgrass managers considering incorporating them into their weed management programs this year.
Coastal is a new herbicide mixture from Sipcam Agro that contains prodiamine (WSSA Group 3), imazaquin (WSSA Group 2), and simazine (WSSA Group 5). This mixture can be applied preemergence to control many grassy and broadleaf weeds including crabgrass (Digitaria spp), annual bluegrass (Poa annua), and goosegrass (Eleusine indica). Coastal is labeled for use in many turfgrass systems including golf courses, athletic fields, home lawns and sod farms; Coastal can be applied to several turfgrass species including bermudagrass (Cynodon spp.), zoysiagrass (Zoysia spp.), St. Augustinegrass (Stenotaphrum secundatum), and centipedegrass (Eremochloa ophiuroides) as well. Coastal offers early-postemergence control of several weed species, particularly annual bluegrass. Depending on geography, Coastal should be applied between September 15th and May 31st at rates of 48 to 64 fl oz/A. Researchers at the University of Tennessee observed 100% control of annual bluegrass 24 weeks after treatment of Coastal applied twice at 32 fl oz/A (Figure 1). If used at an early postemergence timing, a single application of Coastal at 60 to 64 fl oz/A is recommended. Coastal can hamper spring transition of warm-season turfgrasses. Therefore, use as turfgrass is emerging from dormancy is not recommended.
Cheetah Pro is a new herbicide from NuFarm that offers an alternative to glyphosate on select weeds. Cheetah Pro contains 24.5% glufosinate (WSSA Group 10), the same active ingredient in Finale. However, Finale (11.3% glufosinate) is less concentrated than Cheetah Pro, so turfgrass managers must carefully read product labeling to identify optimal Cheetah Pro application rates. As a non-selective herbicide, Cheetah Pro can be applied postemergence to dormant bermudagrass at rates of 24 to 82 fl oz/A based on weed size and growth stage. The herbicide is labeled for control of nearly 200 weed species including common winter annual weeds such as annual bluegrass, henbit (Lamium amplexicaule), and common chickweed (Stellaria media). Cheetah Pro is rainfast within four hours and has low soil residual, making it an excellent product for use preplant in landscape beds. Cheetah Pro is labeled for both commercial and residential turfgrass use. Research at the University of Tennessee has shown that herbicides containing glufosinate can control certain populations of annual bluegrass that have evolved resistance to glyphosate. Sequential applications of Cheetah Pro may be required to control certain weed species and can be applied as early as five days after initial treatment. In a field trial conducted at the University of Tennessee in 2020, applications of Cheetah Pro from 56 to 82 fl oz/A resulted in greater annual bluegrass control (93 to 95%) two weeks after treatment than either Monument (trifloxysulfuron) or Certainty (sulfosulfuron; Figure 2).
Crew is a new herbicide mixture from Corteva Agriscience that contains isoxaben (WSSA Group 29) and dithiopyr (WSSA Group 3) labeled for preemergence control of many broadleaf and grassy weeds including crabgrass, goosegrass, and annual bluegrass. Additionally, Crew can be used for postemergence control of newly emerged crabgrass through the one-tiller growth stage. Crew is labeled for use in both residential and commercial areas comprised of bermudagrass, zoysiagrass, seashore paspalum (Paspalum vaginatum), Kentucky bluegrass (Poa pratensis), perennial ryegrass (Lolium perenne), or tall fescue (Festuca arundinacea). However, the herbicide should not be applied to turfgrass stands that have been sodded, sprigged, or reseeded until they are fully established. Additionally, turfgrass managers should delay seeding or sodding areas treated with Crew until 8 to 12 weeks after application. Crew is labeled for use at 150 to 200 lbs/A. Research conducted the University of Tennessee in 2019 highlighted that by late August, single applications of Crew in mid-March (150 or 200 lbs/A) controlled smooth crabgrass greater than Specticle G (indazaflam) or Freehand (dimethenamid + pendimethalin) at rates of 150 lbs/A.
Another new Corteva Agriscience product, GameOn, is a mixture of 2,4-D choline, fluroxypyr, and halauxifen-methyl (Arylex™). All of these active ingredients are synthetic auxin herbicides (WSSA Group 4) with efficacy for postemergence control of broadleaf weeds such as plantain (Plantago spp.), clover (Trifolium spp.), and dandelion (Taraxacum officinale). Similar to Crew, GameOn is labeled for use on many turfgrass species including bermudagrass, creeping bentgrass (Agrostis stolonifera), Kentucky bluegrass, perennial ryegrass, and tall fescue. GameOn can be used on bermudagrass; however, the height-of-cut must be greater than 0.5 inches and application rate is capped at 3 fl oz/A (compared to 4 fl oz/A on other grasses). GameOn is rainfast within two hours of application and unlike other 2,4-D containing herbicide mixtures, the product is formulated to reduce odor. Turfgrass managers should be advised that GameOn should not be applied to bermudagrass when breaking dormancy in the spring. Additionally, seeding areas treated with GameOn should be delayed for a minimum of three weeks after application. Lastly, turfgrass managers should be aware that the product is currently not labeled for use on residential turf.
Manuscript is a systemic herbicide from Syngenta with the active ingredient pinoxaden (WSSA Group 1). Manuscript is a postemergence product labeled for use on bermudagrass and zoysiagrass golf courses, home lawns, sports fields, and sod farms. On sod farms, Manuscript may be applied to St. Augustinegrass. Manuscript is labeled for both broadcast and spot treatment application. However, spot treatments 9.6 fl oz/10,000 ft2 (applied twice) or 19.2 fl oz/10,000ft2 (applied once) are recommended for maximum weed control. Manuscript must be applied in combination with the spray surfactant Adigor. Manuscript is only effective on grassy weeds such as large and smooth crabgrass or tropical signalgrass (Urochloa subquadripara). Manuscript is a fast-acting herbicide on susceptible weeds with symptoms typically manifesting within a few days after treatment. Researchers at the University of Tennessee are actively exploring Manuscript use for control of common grassy weed species in warm-season turfgrass.
Vexis is a new granular herbicide from PBI Gordon that contains the acetolactate synthase inhibiting herbicide pyrimisulfan (WSSA Group 2). Vexis is labeled for postemergence control of sedge (Cyperus spp.), kyllinga (Kyllinga spp.), rush (Juncus spp.), and select broadleaf weeds on nearly all cool and warm season turfgrasses used for golf courses, athletic fields, and home lawns. Initially, Vexis will be available to turfgrass managers in a 2 lb shaker can designed for spot treating individual weeds (rather than broadcasting across an entire area). One shaker can supplies enough product to treat an area as large as 500 square feet. Turfgrass managers must delay seeding or sodding for three weeks after Vexis treatment; when using the product on newly established turfgrass a three-week delay is required as well. Unlike most granular herbicides, Vexis can be applied to wet or dry foliage, but will require irrigation (or rainfall) within 48 hours after application.
*This article was modified from a piece drafted by the same authors for publication in SportsTurf Management.READ THE ISSUE