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While preemergence herbicides control crabgrass spp., goosegrass and sandbur, we usually encounter situations during the summer months where postemergence control of grass weeds is necessary. Tall fescue and warm-season turfgrasses have excellent tolerance to most preemergence herbicides. However, turfgrasses widely vary in their tolerance to postemergence grass control herbicides, and adverse injury can occur during the hot, humid days of summer. Proper selection of the appropriate postemergence grass control herbicide depends upon the turfgrass and weedy grass species.

Bermudagrass. For years, MSMA and DSMA has been the standard postemergence herbicide for control of annual grass weeds. For crabgrass spp. control, plan on making two applications, spaced 5 to 10 days apart, at rates shown on the label. Most MSMA and DSMA formulations are premixed with a nonionic surfactant. If the concentration is sufficient to supply a 0.25% v/v (2.0 pts. in 100 gallons of water) surfactant concentration, then no additional surfactant is necessary. Check with your chemical dealer to determine the surfactant concentration of the MSMA or DSMA product you use. If the formulation has no surfactant add a high quality (80% active ingredient or greater) nonionic surfactant to achieve a 0.25% v/v concentration. MSMA and DSMA can cause objectionable, but temporary, injury to bermudagrass, particularly at air temperatures > 90 F. Try to spray on days where air temperatures are < 90 F. Adding iron products to MSMA has been shown to lessen MSMA injury to turfgrasses, but recent research in Mississippi indicates that it may also be reducing annual grass control. Repeat applications of MSMA will also control sandbur, but are ineffective for control of goosegrass. For goosegrass control, add low rates of Sencor 75 Turf, and repeat the application as discussed above. On golf courses only, Illoxan can be used on bermudagrass fairways, tees and greens for postemergence control of goosegrass. However, Illoxan will not control crabgrass. Tank-mixes of MSMA with Illoxan are not advisable since MSMA has been shown to decrease the effectiveness of Illoxan in controlling goosegrass. Crabgrass can also be controlled in bermudagrass with Drive. Drive is a relatively new turfgrass herbicide that also has been shown to selectively control torpedograss in bermudagrass. Unlike MSMA/DSMA a single application of Drive will control emerged crabgrass up to about the second tiller growth stage, and is less injurious to bermudagrass than MSMA. Drive may also be applied at the time of seeding or sprigging bermudagrass, or as soon as 7 days after bermudagrass emergence. Drive will not control goosegrass. Manor may be used in bermudagrass for 'Pensacola' bahiagrass control, while Image can be used for the control of sandbur spp.

Centipedegrass. Vantage is the standard herbicide used for the postemergence control of annual grass weeds in this turfgrass. A single application will usually control crabgrass, goosegrass, sandbur and numerous other annual grass weeds. Repeating the application will also suppress both bermudagrass and bahiagrass. Vantage can be applied to established, actively-growing centipedegrass, and to newly-established centipedegrass after 3 inches of new stolon growth has occurred. On centipedegrass sod farms only, Envoy can be used for postemergence annual grass control and to suppress bermudagrass. Research conducted in the southern states has shown that Envoy is slightly better than Vantage in suppressing bermudagrass. Other options for grass control in centipedegrass include Manor for Pensacola bahiagrass control, and Image for control of sandbur spp.

St. Augustinegrass. Postemergence herbicide options for annual grass control in St. Augustinegrass are very limited. Asulox is registered for use on St. Augustinegrass sod farms and will control crabgrass and goosegrass. However, the continued availability of Asulox is questionable. If you plan to use Asulox, I would highly recommend that you discuss this need with your herbicide supplier. Prograss or Prograss + atrazine tank-mixes can be used for the postemergence control of bermudagrass in St. Augustinegrass. Repeat applications are necessary during the summer months for extended control of bermudagrass. Pensacola bahiagrass can be controlled in St. Augustinegrass with Manor. However, Manor will not control crabgrass or goosegrass. Image can be used in actively-growing St. Augustinegrass for sandbur spp. control.

Zoysiagrass. Similar to bermudagrass, MSMA and DSMA has been the standard postemergence herbicide of control of annual grass weeds in zoysiagrass. But unlike bermudagrass, zoysiagrass can be severely injured by MSMA/DSMA, particularly at elevated temperatures in the summer months. Additionally, zoysiagrass cultivars vary widely in their tolerance to MSMA. Research conducted in Georgia by B. J. Johnson showed that 'Emerald' was more sensitive to MSMA than 'Meyer'. 'Matrella' tolerance to MSMA was intermediate of that observed with Emerald and Meyer. There have been a high number of new zoysiagrass cultivars introduced into the turfgrass market, and the tolerance of these cultivars to MSMA is not well documented. Before using MSMA on a new zoysiagrass cultivar, I highly suggest you check with your turfgrass supplier or apply a test strip of MSMA and observe the grass over a period of 2 to 3 weeks. Please see the previous comments for MSMA shown in the bermudagrass section above. Drive may also be used in zoysiagrass for crabgrass spp. control. Established zoysiagrass has outstanding tolerance to Drive, and it may also be used at the time of seeding or sprigging, or as soon as 7 days after zoysiagrass emergence. Another option for zoysiagrass, and one that controls a broader spectrum of annual grass weeds than Drive is Acclaim Extra. This postemergence graminicide has herbicidal activity only on grass weeds. Acclaim Extra can be applied to either actively-growing established or newly-sprigged zoysiagrass. For best results it should be applied to small grass weeds in the early summer months. Repeat applications of Acclaim Extra every 30 days will also suppress common, but not hybrid, bermudagrass in zoysiagrass. Bermudagrass can also be suppressed in zoysiagrass with low rates of Fusilade II applied every 30 days during late spring and early fall months. Other options for grass control in zoysiagrass include Manor for Pensacola bahiagrass control, and Image for control of sandbur spp..

Tall Fescue. MSMA and DSMA has been the standard postemergence herbicide of control of annual grass weeds in tall fescue. But similar to zoysiagrass, tall fescue can be severely injured by MSMA/DSMA, particularly at elevated temperatures in the summer months. If MSMA is to be used on tall fescue, applications should be made during the late spring and early summer months before air temperatures exceed 90 F. Please see the previous comments for MSMA shown in the bermudagrass section above. Drive may also be used in tall fescue for crabgrass spp. control. Established tall fescue has excellent tolerance to Drive, and it may also be used at the time of seeding, or as soon as 7 days after tall fescue emergence. Similar to zoysiagrass, Acclaim Extra may be used in tall fescue for the postemergence control of crabgrass, goosegrass, fall panicum, foxtail spp. and several other annual grass weeds. Acclaim Extra can be applied to either established or newly-emerged (4 weeks old) tall fescue. For best results it should be applied to small grass weeds in the early summer months. Repeat applications of Acclaim Extra every 30 days will also suppress common, but not hybrid, bermudagrass in tall fescue. Bermudagrass can also be suppressed in tall fescue with low rates of Fusilade II applied in the spring after bermudagrass has emerged from winter dormancy, and again in the September-October time frame.

Turfgrass managers do have good options to control annual grass weeds in most turfgrass species. St. Augustinegrass is the exception and all efforts should be made to properly use a preemergence herbicide for annual grass control. One perennial grass that continues to elude control is dallisgrass. Dallisgrass is difficult to control, but it can be controlled with 3 applications of labeled rates of MSMA, each applied 5 days apart. This program will control dallisgrass but can cause serious injury to zoysiagrass and tall fescue. Unfortunately, there is no other selective option. Repeat applications of Vantage will provide only temporary dallisgrass control in centipedegrass. In St. Augustinegrass, there is no selective control. No one likes spot treating dallisgrass with Roundup Pro, but keep in mind that control options for this perennial weed are very limited. With minor infestations of dallisgrass, it may be better to "bite the bullet" and spot treat with Roundup Pro.