Weeds Pages
A dense, vigorously growing, competitive stand of turfgrass will resist invasion by weeds. Integrated weed management focuses on selecting, establishing, and maintaining a competitive stand of turfgrass. While it is difficult to eliminate all weeds from turf, in highly maintained turf it is possible to prevent large irregular patches of weeds, which make turf unattractive and reduce its utility.
The objective of an integrated weed management program is to keep weed populations below levels that are incompatible with the purpose of the turf. The first step is preparing the site properly and choosing an appropriate turfgrass species for the location, followed by cultural practices that contribute to turf vigor, such as proper irrigation, mowing, fertilization, thatch removal, and aeration. The increased vigor allows turf to better withstand insect, disease, and nematode damage and to recover more quickly. Healthy turf can also out-compete weeds and reduce the chances of their becoming established. Herbicides are used as tools in turf management where high-quality turf is required; however, their use should be integrated with a good cultural program.
Selecting a Turfgrass
Turf species and cultivars vary in their adaptability to different areas of California. Choosing a well-adapted cultivar to plant will be one of your most important weed management decisions (see section on TURFGRASS SPECIES or refer to the UC Guide to Healthy Lawns. Cool-season species (bentgrass, bluegrass, perennial ryegrass, and tall fescue) are most competitive in the coastal and northern regions of California; some of the newer cultivars of perennial ryegrass, Kentucky bluegrass and tall fescue are more competitive and grow better than the old cultivars. Warm-season species (bermudagrass, St. Augustinegrass, zoysiagrass, seashore paspalum, and dichondra) are most competitive with weeds in the interior valleys and desert regions. When turf species are planted in areas where they are not well adapted, they require greater care (e.g., management skills and resources) to grow and maintain and are more susceptible to invasion by weeds. Irrigation, mowing, and fertilization requirements vary for each turf species and must be carefully followed to maintain their competitive edge against weed invasions.
Turf Establishment
(Before planting turf or when renovating weedy turf) Before planting, annual weeds can be controlled by irrigating to germinate weed seeds in soil, followed by shallow cultivation or application of a contact herbicide. Repeat this process two or three times to improve the chances of establishing a turfgrass with a minimum of weeds. Planting turfgrass sod in well-prepared soil that has been cultivated and amended to improve water-holding capacity in sandy soil or to improve drainage in clay soils will decrease annual weeds. Poor drainage favors some weeds such as annual bluegrass, broadleaf plantain, crabgrass, curly dock, nutsedge, and red sorrel.
Populations of some perennial weeds such as dallisgrass, bermudagrass, and nutsedge can be reduced before planting turf by cultivating in summer and keeping the soil completely dry to dehydrate the propagules (stems, rhizomes, tubers). Rework the soil to bring up new propagules, but be sure to keep the soil dry; three to four cultivations a week or more apart may be needed for best results.
Managing Established Turf
Turfgrass can be established and maintained to discourage weeds in the turf or to decrease chances for weed invasion. Any condition that exposes the soil surface to additional light makes that area more susceptible to weed invasion. Factors that contribute to poor turf quality and vigor include overwatering or underwatering, mowing too low or too high, low fertility, excessive wear, disease or insect damage, soil compaction, and excessive shading.
Irrigation Management
California has a Mediterranean climate that is characterized by rainfall in winter and spring and very little rainfall in summer and fall. Irrigation is needed, therefore, for both cool- and warm-season turfgrasses. It is very important to follow good irrigation practices, regardless of turfgrass species used, so that optimum growth and development of turfgrass is obtained.
Most turfgrass sites in California are irrigated with a sprinkler irrigation system. A uniform application of water is extremely important for maximum efficiency because it is important to avoid wet and dry spots within the sward. Turf is weakened in wet spots because of poor soil aeration and root disease, which can result in the invasion of shallow-rooted weeds such as crabgrass, annual bluegrass, and oxalis. Runoff from overirrigated areas is wasteful and results in accumulation of water in low parts of the sward. In contrast, dry sites will be characterized by turf of poor color, density, and uniformity that allows the invasion of deep-rooted weeds such as bermudagrass, dandelions, plantains, clover, knotweed, and yarrow.
Proper timing and an adequate amount of irrigation are necessary for optimal growth, maximum quality, and best appearance of the respective turfgrass species. Common warm-season turfgrass species in California include common and hybrid bermudagrass, St. Augustinegrass, kikuyugrass, and zoysiagrass. The most commonly planted cool-season turfgrasses for California are tall fescue, Kentucky bluegrass, and perennial ryegrass. Cool-season turfgrass species require more water than warm-season turfgrass species. Water use rates also vary based on a location's climate (low desert valleys can approach 0.37 inches per day in July, while during the same period turfgrass in northern coastal regions may require only 0.12 inches per day). The table below shows the relative water use rates of turfgrass types for three different locations in California. See local newspapers, your water district, or contact local Cooperative Extension offices for the water required in specific areas.
| IRVINE | DAVIS | UKIAH | ||||
|---|---|---|---|---|---|---|
| MONTH | cool-season
grass |
warm-season
grass |
cool-season
grass |
warm-season
grass |
cool-season
grass |
warm-season
grass |
| January | 1.2 | 1.2 | 0.8 | 0.6 | 0.8 | 0.6 |
| February | 1.6 | 1.4 | 1.5 | 1.1 | 1.1 | 0.8 |
| March | 2.8 | 2.8 | 2.6 | 2.0 | 2.0 | 1.5 |
| April | 4.5 | 3.1 | 4.0 | 3.0 | 2.6 | 2.0 |
| May | 4.6 | 4.0 | 5.1 | 3.8 | 4.1 | 3.0 |
| June | 4.8 | 3.6 | 6.0 | 4.5 | 4.6 | 3.5 |
| July | 5.9 | 4.3 | 6.5 | 4.9 | 5.4 | 4.0 |
| August | 5.0 | 4.0 | 5.7 | 4.2 | 4.7 | 3.5 |
| September | 3.6 | 3.1 | 4.3 | 3.3 | 3.6 | 2.7 |
| October | 2.8 | 1.9 | 3.2 | 2.4 | 2.2 | 1.7 |
| November | 1.8 | 1.5 | 1.4 | 1.1 | 1.0 | 0.8 |
| December | 1.2 | 0.9 | 0.8 | 0.6 | 0.6 | 0.4 |
Key Points for Maximum Irrigation Efficiency:
- Irrigate deeply, but infrequently.
- Irrigate early in the morning. At this time water loss from evaporation is minimal, distribution is usually good because of good water pressure and limited wind, and the risk of disease development is reduced.
- Avoid runoff by matching water application rates to soil infiltration rates (rate water enters soil) or by pulsing (i.e., applying a portion of the water, waiting for it to be absorbed in the soil, and then applying the next portion).
- Use less water (about half as much) in shaded areas than in open sun.
- Remove thatch in spring if it is more than 0.5 inch thick.
Fertilization
Proper fertilization of turfgrass is an important component in producing vigorous, dense growth. Low fertility, especially low nitrogen, is one of the factors that allows weeds to invade turf. For example, clovers tend to grow well in areas of low soil nitrogen because they can fix nitrogen in their roots. Therefore, where clovers are a problem, increase nitrogen fertilization to make the turfgrass more competitive. Most turfgrass species require a total of 4 to 6 lbs of actual nitrogen per 1000 square feet per year. Apply nitrogen about four times during the year when the turf is actively growing (see Table 2). For slow-release fertilizers, make applications at 6- to 8-week intervals; for other fertilizers, applications are made at 4- to 6-week intervals. Use the following guidelines to determine application rates for the different turfgrass species:
| Turfgrass Species | Nitrogen
(lb/1000 sq ft/application)1 |
Period of Active Growth2 |
|---|---|---|
| COOL-SEASON TURF | ||
| bentgrass, colonial | 0.5 | Mar–Jun and Sep–Nov |
| bentgrass, creeping | 0.75–1 | Mar–Jun and Sep–Nov |
| fescue, fine | 0.25–0.5 | Mar–Jun and Oct–Dec |
| fescue, tall | 0.5–1 | Mar–Jun and Sep–Dec |
| Kentucky bluegrass | 0.5–1 | Mar–May and Oct–Dec |
| ryegrass, annual (for overseeding) | 0.75 | Oct–May |
| ryegrass, perennial | 0.5–1 | Feb–Jun and Oct–Dec |
| WARM-SEASON TURF | ||
| bermudagrass, common | 0.5 (spring–summer) | Apr–Sep |
| bermudagrass, hybrid | 0.75–1 | Apr–Sep |
| Tifgreen | 0.75–1 | Apr–Sep |
| Tifway II | 0.75–1 | Apr–Sep |
| Santa Ana | 0.75–1 | Apr–Sep |
| dichondra | 1 | Apr–Oct |
| kikuyugrass | 0.5 | Feb–Nov |
| St. Augustinegrass | 0.5 | Mar–Oct |
| zoysiagrass | 0.25–0.5 | Apr–Oct |
| 1 | Assuming 4 applications per year during period of active growth. |
| 2 | Varies slightly according to location in the state. |
Mowing
Correct mowing height and frequency of mowing is critical for preventing weed invasion. Different turfgrass species have different mowing height requirements. Mowing Kentucky bluegrass too short (less than 1.5 inches) weakens the turf and encourages weed growth. Conversely, mowing it too high (higher than 3 inches) reduces turf density and competitive ability. The table below provides the correct mowing height for the different turfgrass species.
| Turfgrass species | Mowing height (inches) |
|---|---|
| bentgrass, colonial | 0.5–1 |
| bentgrass, creeping | 0.5 or less |
| bermudagrass, common | 1–1.5 |
| bermudagrass, hybrid | |
| Tifgreen | 0.25–0.5 |
| Tifway II | 0.5–1 |
| Santa Ana | 0.5–1 |
| dichondra | not mowed |
| fescue, fine | 1.5 or not mowed |
| fescue, tall | 2–3 |
| Kentucky bluegrass | 1.5–2.5 |
| kikuyugrass | 1–1.5 |
| ryegrass, annual | 1.5–2.5 |
| ryegrass, perennial | 1.5–2.5 |
| St. Augustinegrass | 1–2 |
| zoysiagrass | 0.5–1.5 |
Mow turfgrass so that no more than one-third of the leaf blade is taken off at each cutting. In the summer months, cool-season turfgrasses (Kentucky bluegrass, perennial ryegrass, fine fescue, tall fescue and colonial bentgrass) may be mowed at the higher height to encourage deeper rooting.
Weedy turfgrass areas need to be mowed frequently so that they don't develop a patchy appearance caused by uneven growth of the weeds. Common weeds that require frequent mowing to prevent patchiness and seedhead development are annual bluegrass and annual ryegrass in winter, and crabgrass, dallisgrass, and nutsedge in summer.
Thatch Removal and Aeration
Thatch develops in turfgrass when dead leaves, rhizomes, stolons, and stems accumulate faster than they are decomposed. Creeping species such as bentgrass, bermudagrass, zoysiagrass, St. Augustinegrass, and kikuyugrass can produce a thick thatch. Removing thatch increases the turfgrass vigor, reduces scalping by the mower, and gives a more uniform appearance to the turfgrass. Thatch can reduce the effectiveness of preemergence herbicides by either (1) binding with the herbicides and making them ineffective or (2) increasing degradation of the herbicides as a result ofthe increased activity of microorganisms living in the thatch.
Thatch removal (by verticutting) should be done before preemergence herbicides are applied; otherwise the herbicide will be removed or its activity will be decreased. The same principle applies to aeration. Apply herbicides after aeration to get maximum control of the weeds.
Monitoring
Regular weed surveys (winter, spring, and summer) will help determine what species are present, their approximate population levels, and what types of management practices may be necessary. Use Weeds of the West, Weeds of California and Other Western States, UC ANR Publication 3488; the UC IPM Weed Photo Gallery, or the UC Guide to Healthy Lawns.
Use a form such as the following one to keep written records of monitoring results. (This form can also be adapted to use in a spreadsheet computer program.) A written weed history will aid in making future weed management decisions.
| WEED SURVEY FORM | ||
|---|---|---|
| Date ______________________ | Location ______________________________ | |
| ANNUAL SPECIES | ||
| ( ) annual bluegrass | ( ) knotweed | ( ) scarlet pimpernel |
| ( ) black medic | ( ) large crabgrass | ( ) smooth crabgrass |
| ( ) burclover | ( ) malva | ( ) spotted spurge |
| ( ) common chickweed | ( ) pineappleweed | ( ) spurweed |
| ( ) goosegrass | ( ) purslane | ( ) wild barley |
| ( ) ___________________ | ( ) ___________________ | ( ) ___________________ |
| PERENNIAL SPECIES | ||
| ( ) bermudagrass | ( ) English daisy | ( ) oxalis |
| ( ) broadleaf plantain | ( ) green kyllinga | ( ) nutsedge, purple |
| ( ) dallisgrass | ( ) kikuyugrass | ( ) nutsedge, yellow |
| ( ) dandelion | ( ) ___________________ | ( ) white clover |
| ( ) ___________________ | ( ) ___________________ | ( ) ___________________ |
| ( ) Check for frequency of occurrence: L = low, M = medium, H = high | ||
Herbicides
Herbicides are an effective tool where high quality turf is desired. However, they must be applied with care and accuracy and in the context of a good overall turf management program. Before using any herbicide, carefully review the label for conditions of use including rates, methods of application, and precautions. Never use an herbicide in any manner contrary to its label, and be sure that the herbicide will not injure the turfgrass species (see table on Sensitivity of Turf Species to Herbicides).
When using any herbicide for the first time, apply it at the recommended rate on a limited area to make sure it is successful under local conditions. Excessive rates, improper timing, or application errors of selective herbicides can injure or kill desirable turf. Insufficient application, on the other hand, usually results in failure or incomplete weed control. Be aware of formulation changes for the herbicide; new formulations may result in turf injury even though no injury was noted in previous formulations.
In some cases adjuvants are used with herbicides. Adjuvants are compounds that modify a spray solution. These include wetting agents, surfactants, spreaders, emulsifiers, and solvents. Adjuvants can enhance herbicide activity and/or reduce herbicide selectivity. Some adjuvants alone can cause injury to turf. Adjuvants should only be used when called for by the product label.
Herbicides can be broadcast or used for spot treating areas. The extent of the weed infestation will determine which application method to use. Broadcast applications can be made either by spraying herbicides mixed in water or by applying herbicides fixed to granules. Small, scattered weed infestations should be controlled with spot applications. Larger and more uniform weed infestations should be controlled with broadcast applications. To increase the uniformity of granular applications, apply one-half of the required herbicide over the entire area to be treated in one direction (north-to-south) and the other half over the entire area in the perpendicular direction (east-to-west). Before making broadcast spray applications, carefully calibrate the sprayer to ensure accuracy. See The Safe and Effective Use of Pesticides, UC ANR Publication 3324, for additional information.
Spot treatment with selective herbicides such as 2,4-D is useful in small areas. Be sure to apply the recommended rate and concentration. Be careful not to prolong application over individual spots, as over-application can occur and result in turf injury to the surrounding area. Spot treatments are also useful with nonselective herbicides such as glyphosate when used to control individual clumps of weeds such as tall fescue, dallisgrass, smutgrass, or nutsedge. When applying the herbicide, apply just enough spray to wet the leaves of the weed. Do not allow the application equipment to drip or leak between spot applications. Also, do not walk through the treated area onto untreated turf. Severe turf injury can result from the herbicide dripping onto the turfgrass or by being moved on the soles of shoes. If the weed is taller than the turf, the herbicide can be applied with a sponge or wick wiper, giving a selective application to the weed.
Site Preparation
Three herbicides that can be used before planting turfgrass (preplant) are glyphosate (Roundup Pro), dazomet (Basamid), and metam sodium (Vapam). When preparing a new site for turfgrass, glyphosate, a systemic herbicide, is used primarily for control of existing perennial weeds. Dazomet and metam sodium are soil fumigants that are usually applied to bare soil. Vaporproof coverings like polyethylene will increase the control from the soil fumigants dazomet and metam sodium. Preplant fumigation of a site can kill bermudagrass, nutsedge, and other perennials, as well as all existing annual plants and many germinating seeds.
Newly Established Turf
Siduron (Tupersan) can be used on newly seeded or established, cool-season turfgrass for control of broadleaf seedlings and warm-season grasses. Bromoxynil (Buctril) can be applied to newly emerged turf when it is about one month old to control seedling broadleaf weeds. Postemergence herbicides such as 2,4-D, dicamba, fluroxypyr, or triclopyr can be used for broadleaf control once the turf has produced several tillers and has been mowed two or three times. In general, preemergence herbicides can be used when the turfgrass is well established; there are a few exceptions for earlier usage.
Established Turf
Herbicides may be applied before (preemergence) or after (postemergence) weeds emerge. Each herbicide may have restrictions on certain species of turfgrass, usage sites (e.g. recreational, commercial, or residential turf), and availability to purchase (e.g. licensed applicator). Always read and follow the label recommendations. Weed control is often rate dependent. More information about each herbicide is included in the HERBICIDE TREATMENT TABLE.
Putting two or more herbicides into the same spray tank is called a tank mix and is a common practice in several turfgrass situations. Tank mixes can be two preemergence herbicides, two postemergence herbicides, or one of each kind. Herbicide labels suggest or specifically list which herbicides can be tank mixed with a product. For tank mixes, observe all directions for use on all labels, and employ the most restrictive limits and precautions. Never exceed the maximum active ingredient (a.i.) on any label when tank mixing products that contain the same a.i.
There are dozens of formulations and combinations of herbicides that are sold as a prepackaged mix in the turfgrass marketplace. These products are designed to increase the weed spectrum of activity, the safety to the turfgrass species or site, or both. These guidelines do not list all herbicide products because they are too numerous and change too rapidly, however their active ingredients remain fairly constant and are described here. These mixes typically include various combinations of the following: 2,4-D or 2,4-DP, dicamba, MCPA, MCPP, MSMA, carfentrazone, triclopyr, fluroxypyr, and quinclorac.
Preemergence Herbicides
Preemergence herbicides used to control weeds in turf are applied to the soil before the weed seeds germinate; most are moved into the top 1 to 3 inches of soil by rain or irrigation where they will be taken up by the roots and shoots of the emerging weeds. Timing of application and sprinkler irrigation afterwards are key to achieving the best results. Soil residual activity depends upon the herbicide and rate of application. The general range of activity is 2 to 8 months with most herbicides lasting about 3 to 4 months. Preemergence herbicides include:
Atrazine (Atrazine), which is labeled for use in sod production only, is used exclusively in St. Augustinegrass or zoysiagrass for control of annual broadleaf weeds and some annual grasses.
Bensulide (Bensumec) is used on many species of established turf for control of annual grasses. Apply it before initial weed seed germination; the timing of the application depends on location in the state and the weed species targeted. Bensulide gives 4 to 6 months control of annual grasses and will inhibit germination of overseeded grass.
Dithiopyr (Dimension) is used on many species of established turf for control of annual grass and some seedling broadleaf weeds. Used primarily as a preemergence herbicide to control germinating crabgrass, annual bluegrass, spurge, and oxalis, but it will also control crabgrass (large or smooth) seedlings up to the 3-leaf stage. May be combined with MSMA for postemergence crabgrass control.
Ethofumesate (Poa Constrictor, Prograss) is a translocated, selective herbicide that controls several annual grass and broadleaf weeds. Primary use is annual bluegrass management. It has both preemergence and early (two-leaf stage) postemergence activity and is most effective in programs that use both timings. May be used on home lawns, golf courses (not putting greens), and is safe for most turfgrasses except zoysia and fine fescue. Must be applied by a licensed applicator.
Isoxaben (Gallery) is used on many species of established turf for the control of many broadleaf weeds. Apply it in late summer to early fall for winter annuals or in early spring for summer annuals or perennial weed seedlings. Provides 6 to 8 months of control.
Napropamide (Devrinol) effectively controls crabgrass and many other annual weeds before emergence. It is currently registered on dichondra, warm-season turf and tall fescue.
Oryzalin (Surflan) controls annual grasses and some broadleaf weeds in warm-season turf and tall fescue. Although labeled for use in tall fescue, oryzalin should not be applied to tall fescue under stress or roots will be inhibited. For this reason, other preemergence herbicides are recommended. Because it has long residual activity; a summer application may prohibit germination of a fall overseeding of winter annual grass.
Oryzalin+benefin (XL 2G) is a granular formulation that combines two dinitroaniline preemergence herbicides for increased weed-spectrum activity.
Oxadiazon (Ronstar) has three formulations with different restrictions in turfgrass. Ronstar G is registered for use in landscape and established warm-season and most cool-season turf species. Ronstar 50 WSP and Ronstar FLO are registered for landscape sites and only dormant bermudagrass, St. Augustine, and zoysiagrass. Oxadiazon is a good preemergence for annual broadleaf and grass weed control. Primarily used for crabgrass, annual bluegrass, annual ryegrass and bromegrasses. Controls many broadleaf weeds including groundsel and other composites, shepherd's purse and other mustards, and little mallow (malva). It is fairly effective on spurge and creeping woodsorrel but does not control chickweed. Ronstar's mode of action is different from most other preemergence herbicides that are root inhibitors. Ronstar is a shoot inhibitor, which is useful on newly sprigged bermudagrass, when spread by creeping stems and root formation is desirable. Ronstar may be used in fairways, parks, golf courses, and non-residential lawns. It is not registered for use on home lawns and should not be used on golf greens. It is only available to licensed applicators.
Pendimethalin (Pre-M, Pendulum, Pendulum AquaCap) is used on many species of established turf to control many broadleaf and grass weeds including crabgrass, foxtail, annual bluegrass, oxalis, and spurge. Because of its long residual period, the turf should not be overseeded with grasses for 8 to 12 weeks after application.
Prodiamine (Barricade) is used on many species of established turfgrass to control annual grasses and many broadleaf weeds, including oxalis and spurge. It is very insoluble in water and lasts for a long time, giving good control. It will interfere with overseeding of grasses for 4 to 10 months, depending on the rate used. Turfgrass must be well established before prodiamine is used or roots will be inhibited.
Pronamide (Kerb) is selective herbicide used for preemergence or early postemergence control of annual bluegrass in bermudagrass turf. It is also used to remove perennial ryegrass from warm-season turf, especially bermudagrass during spring transition at 50% greenup. This herbicide is also effective on chickweed. Pronamide is not registered for use on residential lawns and is only available to licensed applicators.
Siduron (Tupersan) is a preemergence herbicide that can be applied at planting, on newly planted, or established cool-season turfgrass (fescue, bluegrass or ryegrass) to control seedlings of warm-season weeds, particularly crabgrass, bermudagrass, or kikuyugrass. Its primary use is in turf renovation where bermudagrass or kikuyugrass is killed with glyphosate and a cool-season grass is planted. This product is only available to licensed applicators, but it can be used on homeowner lawns.
Pre- and Postemergence Herbicides
There are several herbicides for use in turfgrass that have both pre- and postemergence weed control activity. They are dithiopyr, ethofumesate, and pronamide. Their descriptions are listed under the category of main usage.
Postemergence Herbicides
Postemergence herbicides used in turfgrass weed control either translocate systemically or act as contact herbicides. Herbicides that translocate penetrate the leaves and stems, move in the vascular system, and eventually reach a site of action where they interfere with plant processes, ultimately killing the weeds. Herbicides that translocate include 2,4-D, MCPA, fluazifop, glyphosate, mecoprop, and MSMA. Some translocated herbicides such as dicamba, fluroxypyr, and triclopyr also have some soil activity and can be taken up by roots. Contact herbicides like bromoxynil, carfentrazone, and bentazon kill only the plant tissues touched by the spray, although bentazon does have some soil activity. Movement within the plant beyond the point of contact is limited. Both types of postemergence herbicides must pass through the leaves or shoots of the plant. Some herbicides are rainfast in as little as 2 hours while others should not be irrigated or rained on for at least 48 hours after application. A surfactant (adjuvant) is often added to foliar sprays to help penetrate leaves. Apply to actively growing weeds, and hold off on mowing several days in advance of postemergence herbicide applications.
Bentazon (Bentazon, Broadloom) is a contact herbicide with some soil activity. It helps to control yellow nutsedge and selected broadleaf weeds in turf. Repeated applications are necessary for best results.
Bispyribac-sodium (Velocity) is a selective postemergence herbicide for control of annual bluegrass, roughstalk bluegrass, and certain broadleaf weeds in golf courses and sod farms. It is used in creeping bentgrass and perennial ryegrass (permanent, not overseeded).
Bromoxynil (Buctril) is a contact herbicide used for the control of many young broadleaf weeds. It is the least phytotoxic of the postemergence herbicides to newly seeded grass, yet controls broadleaf weeds when they are small seedlings. It can also be used in established turfgrass but not bentgrass greens. May be tank mixed with other broadleaf herbicides such as 2,4-D, MCPP, dicamba, or MSMA to increase the spectrum of weed control.
Carfentrazone (QuickSilver) is a contact broadleaf herbicide that causes a quick burndown of weeds when temperatures are moderately warm. Control is still achieved in cold weather but takes longer. Does not control chickweed. Can be used in cool- and warm-season turfgrasses. It is also labeled for moss control. Often sold as a prepackaged mix (Power Zone, Speedzone) with other systemic, broadleaf weed killers such as 2,4-D, MCPA, MCPP, or dicamba.
Chlorsulfuron (Corsair) controls many broadleaf weeds, including wild carrot, wild garlic, and wild onion. Control of weed species is rate dependent. Can be used on all turfgrass species except tall fescue, ryegrass, and dichondra, though some precautions are necessary for turfgrass safety. This herbicide is only available to licensed applicators but may be used on home lawns.
Clopyralid (Lontrel) is a translocated, broadleaf herbicide that primarily controls weeds in three plant families: the bean and pea family (which includes clovers), the nightshade family, and the sunflower family (which includes dandelion, composites and thistles). It is particularly effective on hard-to-control thistles, such as yellow starthistle. It is combined and packaged with triclopyr (Confront) for control of additional broadleaf weeds. Clopyralid use is restricted to golf courses only where clippings will not be used in off-site composting. Clopyralid is also packaged and sold in combination (Millenium Ultra 2) with other postemergence herbicides (2,4-D, dicamba, and MSMA).
Dicamba (Banvel) is a foliar-applied, translocated, broadleaf herbicide that also has soil activity. Do not apply high rates or make repeated applications over the root zones of susceptible shrubs and trees. Spray dicamba on calm days to avoid drift onto susceptible plants. Can be used in cool- and warm-season grasses. Often packaged and sold in combination with other broadleaf weed killers (2,4-D, MCPP, triclopyr) to increase the spectrum of weed control.
Ethofumesate (Poa Constrictor, Prograss) is a translocated, selective herbicide that controls several annual grass and broadleaf weeds. Primary use is annual bluegrass management. It has both preemergence and early (two-leaf stage) postemergence activity and is most effective in programs that use both timings. May be used on home lawns, golf courses (not putting greens), and is safe for most turfgrasses except zoysia and fine fescue. Must be applied by a licensed applicator.
Fluazifop (Fusilade II, Ornamec) is a translocated, selective herbicide that controls most annual and perennial grasses, but will not control annual bluegrass. Annual grasses are easiest to control when young. Higher rates of application and repeat treatments are necessary for control of perennial grasses. Its effectiveness is reduced when grasses are under moisture stress. It is used primarily to control grassy weeds in broadleaf ground covers, including dichondra. This herbicide will injure most turfgrass species and is used primarily to suppress bermudagrass in tall fescue. A non-ionic surfactant must be added to the spray tank.
Fluroxypyr (Vista) is a translocated, selective herbicide that controls several broadleaf weeds including clovers, medics, and creeping woodsorrel in most established warm- and cool-season turf species. This herbicide is fast acting and may injure bermudagrass at higher rates. Do not use on golf course putting greens or tees. Do not use near tree or shrub roots, suckers, or shallow-rooted woody plants or injury will occur. Do not tank mix with 2,4-D amine formulation.
Foramsulfuron (Revolver) selectively removes cool-season grasses (annual bluegrass, perennial ryegrass, tall fescue, etc.) growing in established bermudagrass and zoysiagrass. It also suppresses dallisgrass. For use by licensed applicators only.
Glyphosate (Roundup, KleenUp) is a translocated, nonselective herbicide used for broad-spectrum weed control. Apply it to rapidly growing young annual weeds or to perennial weeds at the flowering stage. This herbicide will injure all turfgrass species and is primarily used to control weeds before planting or in turfgrass renovation.
Halosulfuron (Sedgehammer) is a translocated, selective, postemergence herbicide used for the control of yellow and purple nutsedge and the suppression of green kyllinga. It will require more than one application for control and needs a nonionic surfactant in the spray solution. Safe for use in all established turfgrasses.
MCPA is a translocated, broadleaf herbicide. When used at the same rate as 2,4-D, it is less effective in the control of most weed species but somewhat safer for the turfgrass. It is often mixed with mecoprop and dicamba to increase its effectiveness.
MCPP or mecoprop (Mecomec) is a translocated, broadleaf herbicide. Because of its selectivity, it is generally safer to use on turfgrass than 2,4-D or triclopyr and is the safest postemergence herbicide to use on bentgrass. Controls chickweed, clovers, pearlwort, and prostrate knotweed. Frequently formulated into broadleaf herbicide mixes with 2,4-D and dicamba, but also MSMA, triclopyr, carfentrazone, and quinclorac.
MSMA (MSMA 6) is a selective, translocated herbicide. It is used principally for crabgrass, dallisgrass, nutsedge, and green kyllinga control. It is effective on a couple of broadleaf weeds. May cause temporary discoloration of turf. The degree of MSMA selectivity on turf is determined by temperature and rate. Bermudagrass, bluegrass, and zoysiagrass are most tolerant. Bentgrass and fescues are moderately tolerant. Do not use MSMA on St. Augustinegrass, red fescue, or dichondra. Use is severely restricted so read the label carefully. Product use will be prohibited after December 31, 2013.
Quinclorac (Drive) is a selective, translocated herbicide for control of many broadleaf and grass weeds. It is primarily used to control clovers and large crabgrass (results are inconsistent on smooth crabgrass) and to limit the growth of kikuyugrass in warm-season turfgrass. Tips on mowing and adjuvants are specified. Often formulated and combined with other broadleaf weed herbicides.
Sulfosulfuron (Certainty) is a postemergence, translocated herbicide primarily used in warm-season turf. It controls annual and perennial sedges (including purple and yellow nutsedge and green kyllinga), cool-season grasses (Poa annua, Poa trivialis, perennial ryegrass, and tall fescue), and broadleaf weeds (including chickweed, dandelion, white clover, and lawn burweed) growing in established warm-season turfgrasses including bermudagrass, St. Augustinegrass, zoysiagrass, centipede, and kikuyugrass. It can be used to control Poa trivialis (roughstalk bluegrass) in creeping bentgrass and Kentucky bluegrass; to remove tall fescue from Kentucky bluegrass; and to remove perennial ryegrass from overseeded bermudagrass. It can be used in fairways, commercial and residential lawns, parks, and sod farms.
Triclopyr (Turflon) is a translocated herbicide used to control several broadleaf weeds; it is especially effective on creeping woodsorrel (oxalis) and clovers. Do not use triclopyr on bentgrass or warm-season turf species such as common and hybrid bermudagrasses and kikuyugrass. It is sometimes used in tall fescue lawns to suppress bermudagrass. It has some soil activity, so do not apply high rates or make repeated applications over the root zones of shrubs and trees.
Trifloxysulfuron (Monument) is a selective, translocated herbicide used to control annual sedges, yellow and purple nutsedge, green kyllinga, oxalis, and spurge. It also suppresses crabgrass and dallisgrass. It is harmful to cool-season turfgrass species, so it is used in spring greenup to remove tall fescue, annual and perennial rye, annual bluegrass (Poa annua), and roughstalk bluegrass (Poa trivialis) from bermudagrass, St. Augustinegrass, and zoysiagrass. It can only be used on golf courses, sod farms, and other non-residential turf, such as cemeteries and commercial building sites.
2,4-D is a selective herbicide used for annual and perennial broadleaf weed control. It is applied in spring when weeds are rapidly growing. Additional treatments may be required for late emerging weeds or on perennials. This herbicide is available as an amine or ester formulation. The 2,4-D ester form is used for hard-to-kill perennial broadleaf weeds. Do not use it on newly seeded turf, St. Augustinegrass, bentgrasses, or dichondra. The amine form is generally more selective on turfgrass and is less subject to drift problems to nontarget species. 2,4-D is often mixed with several other broadleaf weed killers (MCPP, MCPA, dicamba, clopyralid, carfentrazone, MSMA, triclopyr, quinclorac, etc.) to increase the spectrum of susceptible weeds or provide safety to turfgrass species or sites, or both.
Plant Growth Regulators
Plant growth regulators can be applied postemergence for weed control.
Paclobutrazol (Trimmit) is a plant growth regulator that suppresses the growth of warm- and cool-season grasses. It can only be applied when the desirable turfgrass is actively growing. Some grasses (e.g. Poa annua) can be more retarded in growth than other grasses (e.g., bermudagrass), leading to selective control after prolonged use.
Mefluidide (Embark) is a plant growth regulator used for Poa seedhead control in golf courses.