Demand for professional turf care and expectations for weed-free turfgrass have increased in recent years. Luckily, the number of herbicides available for professional turf care has also increased. Understanding the nuances of where herbicides can be applied and which weeds they control is a daunting task. The following discussion will summarize several new options for weed control in warm-season turfgrasses and hopefully increase your tools for success.

Most southern weed control problems can be broken into three categories:

Professional lawn care companies often offer crabgrass and broadleaf weed control as standard. The client usually pays extra for sedges or unusual or difficult-to-control weeds. From the turf care professional’s perspective, herbicides should be safe for use on most turfgrasses and control a broad range of weed species. In the "old days" products were applied at high use rates to achieve that end. Changes in product lines, release of generic products, and government restrictions on pesticides make it difficult for professionals to find the solution they need in just a few products.

The golden rule of turfgrass weed control is this: "The majority of turf weeds are controlled by good cultural practices, such as cultivar selection, fertility, and mowing, that promote a healthy turfgrass canopy." You must be able to grow grass; not just kill weeds. In addition, your ability to diagnose chronic problems in the environment that limit turfgrass growth is paramount to achieving long-term weed control solutions. The first step of a weed control program is often labeled "identify the weed." This first step is sufficient for many situations but not for turfgrass. The first step in a turfgrass weed control program is "identify the problem that has limited turfgrass competitiveness and fix it." If the underlying problem that has allowed weeds an opportunity for invasion is not fixed, new weeds will simply invade the area after the current weeds are controlled. Be aware that some environments are not suited to turfgrass and discuss alternatives with your client.

Foramsulfuron (Revolver™, Bayer Crop Protection) is a new herbicide for control of Poa and other cool-season grasses like fescues, bluegrasses, and ryegrass. Revolver is also excellent for goosegrass and dallisgrass (Paspalum dilatatum) control but only suppresses crabgrass. Revolver is safe to use at nearly any stage of bermudagrass or zoysiagrass development but may not be safe on all warm-season grasses.

Trifloxysulfuron (Monument™, Syngenta Professional Products) will control young crabgrass plants and provide residual control for one to four weeks. Monument is best used for controlling cool-season grasses like Poa and sedges but also has activity on broadleaf weeds, dallisgrass, and wild garlic to name a few.

Most broadleaf weeds in turf are controlled during dormancy with glyphosate or with selective postemergence herbicides during active turfgrass growth. Products that contain one or more of the following ingredients have been available for many years: 2,4-D, dicamba, chlorsulfuron, clopyralid, MCPP, metsulfuron, and triclopyr. These products often require repeat treatments for hard-to-control weeds like Virginia buttonweed (Diodia virginiana) and ground ivy (Glechoma hederacea). In addition, hormone herbicides like 2,4-D and triclopyr can injure bermudagrass and other warm-season grasses when applied during greenup.

Quinclorac (Drive™ 75DF, BASF) is excellent for white clover (Trifolium repens) and speedwell (Veronica arvensis) but misses several broadleaf weeds. However, it is good to read up on it’s broadleaf activity when you plan to use Drive anyway for postemergence crabgrass control. You may save considerable money if your broadleaf weeds are taken care of by Drive during the crabgrass treatment.

Carfentrazone (Quicksilver™ T&O, SpeedZone™, FMC Corporation) is a new herbicide for control of seedling broadleaf weeds and to improve speed of activity for other herbicides. For example, SpeedZone™ is a mix of hormone-type herbicides and carfentrazone. Quicksilver only has carfentrazone and is safe to use on seedling turfgrass to clean up seedling broadleaf weeds. Few people know of this use for Quicksilver as it is usually marketed as an additive to give quick "burn" symptoms and improve spectrum of weed control with other herbicides.

Monument™ was mentioned for Poa and crabgrass control but this herbicide has appreciable broadleaf control potential. Monument works well on Virginia button weed and some other hard-to-control broadleaf weeds.

Sulfentrazone (Dismiss™, FMC Corporation) is a new herbicide for control of sedges and broadleaf weeds in cool- and warm-season turfgrass. We are still learning about this herbicide but it is known to control several broadleaf weeds when applied postemergence. It’s preemergence activity on a wide range of weeds is less understood. This product offers much more than sedge control and is worth a try.

The number of sedge control products have grown in the past few years. In years past, MSMA, bentazon, and halosulfuron took care of most of our sedge problems. These products have been used successfully for several years but seldom control all sedge species and often require repeat treatments.

Trifloxysulfuron (Monument™, Syngenta) is extremely effective for postemergence control of several sedge species, rushes, and wild garlic.

Sulfentrazone (Dismiss™, FMC Corporation), like Certainty and Monument, Dismiss raises the bar for sedge control compared to our old industry standard herbicides. These three herbicides have all been marketed within the last three years and increase or effectiveness for sedge control considerably.

 Hopefully, these new herbicides will increase your ability to maintain southern turfgrasses. This article was not intended to cover all possible scenarios for weed control in warm-season turfgrass and mention of a particular product was not meant to exclude other suitable products that may be used for the same purpose. Always read and follow chemical label instructions when using any pesticide.

Dr. Shawn Askew is an assistant professor and extension turfgrass weed scientist at Virginia Polytechnic Institute and State University (Blacksburg, VA).