Golfdom, January 2016

Super Science FIGURE 2 Continued from page 39 Bensulide Betasan Bensumec others also is an alternative mode of action to the DNA herbicides Make applications alone or in combination with oxadiazon to enhance the spectrum of weeds controlled Pre packaged combinations or tank mixtures of two pre emergence herbicides with different modes of action enhance the potential to control biotypes of annual bluegrass with suspected resistance Bensulide ethofumesate Prograss and oxadiazon of fer alternative modes of action to DNA herbicides in most cool season turfgrasses for pre emergence control of annual bluegrass Ethofumesate inhibits lipid biosynthesis in susceptible species Sequential applications in fall provide pre or early post emergence control of annual bluegrass Superintendents also may use ethofumesate during establishment of perennial ryegrass and tall fescue to control seedling annual bluegrass Most warm season grasses such as bermudagrass are susceptible to ethofumesate injury and discoloration is a risk if its used during fall overseeding Mesotrione Tenacity is a carotenoid synthesis inhibitor that may control annual bluegrass during establishment of tall fescue or Kentucky bluegrass from seed Applications at seeding provide a competitive growth advantage of tolerant turfgrasses over annual bluegrass during establishment POST EMERGENCE ALTERNATIVES TO SULFONYLUREAS AND TRIAZINES Herbicides may control annual bluegrass after emergence in many turfgrass species Triazines sulfonylureas and several other post emergence herbicides that control annual bluegrass are used in warm season turfgrasses only Superintendents may use amicarbazone Xonerate ethofumesate Prograss and bispyribac sodium Velocity in several cool season turfgrasses for postemergence control of annual bluegrass In the Southern United States late fall applications of these herbicides provide more consistent control than spring timings This is because most post emergence herbicides are more efficacious on annual bluegrass prior to seedhead development or when daytime temperatures are consistently 50 degrees F or higher Atrazine Aatrex others and simazine Princep others are used in warm season grasses in fall for early post emergence control of annual bluegrass These herbicides inhibit photosynthesis at Photosystem II PSII in susceptible weeds and provide about six weeks of residual control depending on application rate Acetolactate synthase ALS inhibitors are widely used in golf course management for annual bluegrass control in tolerant turfgrasses These herbicides include bispyribac sodium Velocity f lazasulfuron Katana foramsulfuron Revolver rimsulfuron TranXit and trifloxysufluron Monument Tribute Total is a combination product that contains multiple ALS inhibitors including foramsul furon that provide post emergence control of annual bluegrass in bermudagrass and zoysiagrass Resistance to ALS and PSII inhibitors has increased exponentially in turfgrass These herbicides have been overused especially in warm season turfgrasses and this has shifted many annual bluegrass populations to resistant biotypes Figure 2 shows the tolerance of a resistant biotype to an ALS inhibitor trif loxysulfuron compared to a susceptible biotype at three weeks after treatment In warm season grasses pronamide Kerb is used for annual bluegrass control as an alternative to these herbicides Pronamide is a mitotic inhibitor that must be absorbed by roots A concern with pronamide is the potential for lateral movement to susceptible cool season turfgrasses Avoid treatments on slopes or to saturated soils if cool season grasses are adjacent to targeted areas Efficacy of pronamide on annual bluegrass also is slow and treatments may take six to eight weeks to obtain acceptable control Flumioxazin Sureguard is another alternative to ALS and PSII inhibitors for annual bluegrass control Flumioxazin is a chlorophyll synthesis PPO inhibitor similar to oxadiazon that is labeled for use only on dormant bermudagrass Applications in late fall provide early post emergence control of annual bluegrass plus residual pre emergence control in winter Turfgrass injury is a major limitation to flumioxazin use The herbicide must be applied to dormant bermudagrass to avoid discoloration during green up Late fall applications of flumioxazin to bermudagrass have induced early winter dormancy These flumioxazin effects may be beneficial for improving turfgrass aesthetics without inhibiting bermudagrass green up in spring In cool season turfgrasses etho 40 Golfdom January 2016 Golfdom com PHOTO BY PATRICK MCCULLOUGH Resistant and susceptible biotypes of annual bluegrass treated with trifloxysulfuron Monument at three weeks after treatment in a greenhouse experiment Note the highest labeled rate is highlighted in red