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Weed Control in Turf

Your lawn may grow more than the beautiful grass you intended.  It may also grow weeds, which prevent your lawn from looking its best. In addition to reducing the aesthetics of your lawn, weeds compete with the desired turfgrass for water, nutrients, and light.  If you don’t control weeds, your lawn will deteriorate over time.  Weeds are often a symptom of a cultural or soil problem that exists in your lawn.  So, weed control involves both removing the weeds and correcting the conditions that led to poor quality turf.

Cultural Control

Growing healthy dense turf is the best way to prevent weeds. Vigorous, healthy turf shades weed seeds so they don’t germinate. Select suitable lawn grasses, fertilize properly (primarily in fall), lime as needed based on soil test recommendations, mow frequently only removing 1/3 of leaf tissue with each cutting, water during establishment and only to keep lawn green during drought.  When you water, be sure to thoroughly soak soil weekly. Frequent, light watering encourages weed encroachment, discourages deep rooting and lowers the environmental stress tolerance of turfgrasses.  Aerate and add compost to improve soil structure. To have a beautiful, healthy lawn you need a basic knowledge of turfgrasses and their cultural requirements. For more detailed lawn care information see cultural lawn care fact sheets.

Chemical Control

Herbicides, chemicals that kill or alter the normal growth of weeds, can be divided into two main groups:  selective and nonselective.  Selective herbicides control the target weed without damaging desirable turfgrasses.  Nonselective herbicides kill all vegetation (including turfgrasses) and are used in lawn renovation or for weeds not controlled by selective herbicides.

Herbicides can be further divided into preemergence and postemergence categories.  Preemergent herbicides are applied prior to germination and weed emergence.  They are typically used for controlling annual weeds.  Posteembergence herbicides are used for controlling weeds that have already emerged from the soil.  They are either systemic or contact in nature.  Contact herbicides affect the plant parts they touch and are not translocated to other parts of the weed.  Systemic herbicides are translocated throughout the plant, so they are effective at killing perennials weeds that can generate new foliage from underground roots.

Herbicides can be applied to foliage or soil.  Postemergence herbicides are usually foliar applied, and preemergence herbicides are soil applied.  A foliar-applied herbicide must contact and be absorbed by the foliage. It is less effective if washed off the leaf surface by rainfall or irrigation.  Soil-applied herbicides can be applied as liquids or granulars and should be watered into the soil following application.

The best way to think about controlling weeds in lawns is to figure out how the weed differs from the desirable grass and use that difference as a means for control.

Annual grass weeds

Summer annual grass weeds are common problems in lawns.  They differ from desirable lawn grasses because they must germinate each year.  Crabgrass and goosegrass are two common summer annuals.  These weeds are controlled with preemergence herbicides that form a chemical barrier in the soil prior to germination or emergence.  The barrier prevents the seedlings from emerging and developing normally.

Table 1. Some preemergence herbicides for the control of summer annual grasses*. 
Generic nameTrade name
BenefinLebanon Balan 2.5G
Benefin and trifluralinTeam
BensulideBensumec
Bensulide + oxadiazonGoosegrass/Crabgrass Control
DithiopyrDimension
OxadiazonRonstar
PendimethalinPre-M, Pendulum, Halts
ProdiamineBarricade
SiduronTupersan

* All the chemical listed in this publication can be used on home lawns, but some are only available to professionals with a certified applicator’s license.

Most preemergence herbicides remain active in the soil, so seeding should be postponed for the amount of time specified on the manufacturer’s label.  Siduron is the only material that can be safety used during or immediately following seeding. Timing of preemergence herbicides is critical.  The best time to apply preemergence herbicides is approximately 10 to 14 days prior to the expected germination period in spring.  Crabgrass begins to germinate when soils are mosite and the temperature in the upper inch of soil reaches 55 o to 58o F at daybreak for four to five days.  Forsythia petal fall is sometimes used as a guideline but may not be reliable.  In Delaware, crabgrass usually germinates between March 15 and April 15.  Depending on the product, time of application, location and rainfall in the spring, reapplication may be necessary within 60 days for season-long control.

If preemergence herbicides are applied too late, you may need to use a postemergence herbicide for summer annual grass control.  Apply postemergence herbicides when the crabgrass or other annual weed is fully visible and apply only to patches of weeds.  As crabgrass becomes larger, it is more difficult to control. You may need to use repeat applications at 10 to 14 day intervals and expect to see some yellowing on desired turfgrass.

Table 2. Some postemergence herbicides for the control of summer annual grasses*. 
Generic nameTrade name
DithiopyrDimension
DSMAMethar 30
Fenoxaprop-p-ethylAcclaim Extra
MSMAMSMA Turf Herbicide
QuincloracDrive 75 DF Herbicide

* All the chemical listed in this publication can be used on home lawns, but some are only available to professionals with a certified applicator’s license.

Broadleaf weeds

Broadleaf weeds differ from desirable lawn grasses in their chemistry and morphology.  Scientists have been able to develop selective products that control broadleaf weeds without harming desirable turfgrasses.  Broadleaf weeds are primarily controlled with herbicides that are applied after weeds have emerged.  These herbicides are applied to foliage and are absorbed into the weed.  These herbicides may be applied as a spray or a granular.  For the most effective control of broadleaf weeds apply posteemergence herbicides as sprays to foliage (don’t wash off).  Granular products should be applied to moist (dew-covered) foliage for optimum control. Posteemergence broadleaf herbicides are most effective when weeds are actively growing (spring and fall) and when temperatures are between 70o and 85oF. Two or more different herbicides are frequently sold in combination to provide control of as many different broadleaf weeds as possible.  It is important to identify the weed(s) to be controlled because many of these herbicides are selective to specific broadleaf weeds. These products have the potential to damage trees, shrubs, flowers, and vegetables if they contact the foliage.  Trees and shrubs are particularly sensitive to dicamba since this herbicide is mobile in the soil and can be taken up by tree roots. Do not use any of these herbicides on newly-seeded turf.  Wait until the new lawn has been mowed at least 3 times before treating (usually about 6 to 8 weeks after seedling emergence).

Table 3. Broadleaf herbicides and herbicide combinations for use in cool-season turf*. 
Generic nameTrade name
2,4-D (amine)Solution Water Soluble, Weedestroy AM-40
Carfentrazone-ethylQuicksilver
Dicamba (amine)Banvel, K-O-G Weed Control
Fluroxypyr (amine)Spotlight
MCPA (amine)MCPA-4 Amine
MCPA (ester)MCPA LV 4 Ester
MCPP (potassium salt)MCPP 4K Turf Herbicide
MCPP (amine)MCPP-p 4 Amine
Triclopyr (ester)Turflon Ester
2,4-D + 2,4-DP (ester)Turf Weed & Brush Control
2,4-D + 2,4-DP + MCPP (amine)Triamine, Triamine Jet Spray
2,4-D + MCPP + dicamba (amine)Trimec Turf Herbicide, Trimec Bentgrass Formula, Triplet Selective, Triplet Hi-D, Triplet SF, Three-Way Selective, Bentgrass Selective, Ortho Weed B Gon, Spectracide, Weed Stop, Bayer Advanced Weed Killer for Lawns
2,4-D + MCPP + dicamba + carfentrazoneSpeed Zone
2,4-D, MCPP, dicamba + sulfentrazoneSurge
2,4-D + triclopyr (amine)Teflon II Amine, Chaser 2 Amine
2,4-D + triclopyr (butoxyethyl ester)Chaser Turf Herbicide
MCPA + 2,4-DP + MCPP (amine)Triamine II
MCPA + MCPP + dicamba (amine)Trupower Selective
MCPA + MCPP + dicamba + carfentrazonePower Zone
MCPA + triclopyr + dicamba (amine)Horsepower
MCPA + triclopyr + dicamba (ester)Cool Power, Three-Way Ester II
Isoxaben (preemergence herbicide)Gallery 75 DF

* All the chemical listed in this publication can be used on home lawns, but some are only available to professionals with a certified applicator’s license.

Nutsedge

Yellow nutsedge is a common turfgrass weed that looks like a grass but is actually a sedge.  It has erect, triangular-shaped stems that are yellow-green, with a thick mid-vein and a waxy surface.  The shallow, fibrous root system often produces many nut-like tubers, which are underground food storage organs.  Each of these tubers can germinate and produce a new plant.  Yellow nutsedge thrives in warm, wet conditions and is often found in low-lying areas of the lawn with poor drainage. If only a few nutsedge plants are present, they can be removed by hand pulling. Remove the entire plant and the root system by digging under the plant.  Where large patches of nutsedge are present, herbicides may be required.  Selective herbicides have been developed that will control this sedge without harming the desirable turfgrass.  Professional lawn care specialists who have a certified pesticide applicators license, have access to two herbicides (Basagran (betas an) and SedgeHammer (halosulfuron) that are highly effective for yellow nutsedge control.

Perennial grass weeds

Perennial grass weeds are not different from desirable turfgrasses except that we don’t want them in our lawn. Bentgrass, which is highly desirable on a golf green is a weed in the lawn, due to its soft, fine-bladed tufty habit.  Wiregrass, common throughout the state, spreads rapidly by tough wiry stems.  This warm season grass goes dormant in the winter. Nimblewill (Muhlenbergia) is a blue-green, thin-bladed grass with wiry stems that forms patches, like bentgrass. Several species of Paspalum can be found in lawns.  One, called Dallasgrass, is a coarse, yellow-green, warm season clump grass.  Seed spikes have characteristic flat, rounded seeds. The only mechanism for control of these perennial grasses is to use a non-selective herbicide, kill the entire patch of lawn infested with the weed, and reseed with desirable turfgrass once the weed is gone.  Glyphosate is a non-selective herbicide that can be used for this type of control.

Table 4. Suggestions for selective control of turfgrass weeds, by weed species.* **   
WeedMaterialApplyRemarks
Annual Bluegrass Poa annua This fine-bladed, bright-green low-growing grass grows vigorously in cool, moist weather. It's the first grass to "greenup" in the spring. Produces many whitish seed heads. Forms patches that may suddenly die out in hot dry weather.bensulideorLate summerApply just prior to expected annual bluegrass germination (late August or early September). Only effective in reducing populations of the annual subspecies of annual bluegrass.
or ethofumesateorSeptember and OctoberFor use on established perennial ryegrass or Kentucky bluegrass or when establishing perennial ryegrass. Two applications are necessary. Do not mix with liquid fertilizers or other pesticides.
Black Medic Medicago lupulina This and similar species of yellow flowering clovers may invade lawns, forming solid patches.Fluroxypyr, or dicamba, or quinclorac, or combination of products containing dicamba, or 2,4-D + triclopyrSpring or fallBest control when weeds are actively growing. Products containing carfentrazone provide faster burndown of black medic than those without carfentrazone.
Chickweed: Common Stellaria media
Mouse ear
Cerastium vulgatum Common chickweed is a mat-forming plant with tiny star-like white flowers. Thrives in spring and fall when cool and moist. Mouse-ear chickweed is similar but is perennial, has hairier stems and leaves, and is more tolerant of summer heat.
MCPP, or dicamba, or combination of products containing MCPP and dicamba, or or 2,4-D + triclopyrSpring or fallBest control when weeds are actively growing.
Chicory Cichorium intybus This somewhat woody perennial has bright blue flowers.2,4-D, or combination of products containing 2,4-D or MCPASpringMost effective on young weeds.
Cinquefoil Potentilla spp. Pronounced "sink-foil"; this common creeping plant reminds people of wild strawberry. But typically has five-part leaves, yellow flowers, and no fruit. Thrives in poor soil.2,4-D + MCPP + dicamba, or 2,4-D + dicamba, or 2,4-D + triclopyrSpringDifficult to kill. May require repeat applications.
Clover Trifolium spp. Spreads by creeping stems, forming conspicuous patches. Blossoms attract bees and other stinging insects.Clopyralid, or fluroxypyr, or dicamba, or quinclorac, or combinations of herbicides containing clopyralid or dicamba, or 2,4-D + triclopyrSpring, summer, or fallBest control when weeds are actively growing. Combinations of herbicides containing carfentrazone provide faster burndown of clover than those without carfentrazone.
Crabgrass: Small (smooth) Digitaria ischaemum Large (hairy) Digitaria sanguinalis This notorious lawn weed consists of two types: smooth and hairy. Both are coarse-bladed, yellow-green in color, and spread out in crab like fashion. They are heavy seed producers. Hot, showery summer weather encourages this pest.Preemergence control: benefin, or benefin + trifluralin, or bensulide, or bensulide + oxadiazon, or dithiopyr, or oxadiazon, or pendimethalin, or prodiamine, or siduronEarly to mid-springBest controlled if herbicides are applied about 2 weeks prior to expected crabgrass germination. d.
Postemergence control: Fenoxaprop-p-ethyl, or methanearsonates (DSMA or MSMA), quinclorac, or dithiopyrEarly summerApply postemergence products only when crabgrass is visible in the stand. Check labels for temperature and plant development restrictions.
Creeping Buttercup Ranunculus repens This stoloniferous perennial has prostrate running stems and erect flower stems that hold the bright golden yellow flowers.2,4-D + dicamba, or 2,4-D, or 2,4-D + MCPP + dicamba, or 2,4-D + 2,4-DP + dicamba, or 2,4-D + 2,4-DPSpring or fallDifficult to kill. May require repeat applications.
Curly Dock Rumex crispus A large basal rosette with leaves tthat have waved or curly edges. Produces at all reddish brown flower stalk.2,4-D + dicamba, or 2,4-D + MCPP + dicamba, or 2,4-D + triclopyrSpring to early summerMature plants difficult to kill.
Dandelion Taraxacum officinale Everyone knows this one, with its bright yellow blossoms and fluffy seed balls. Thrives in thin lawns.2,4-D, or 2,4-D + MCPP + dicamba, or 2,4-D + 2,4-DP + dicamba, or 2,4-D + 2,4-DP, or 2,4-D + triclopyrSpring or fallMay require spring and fall applications.
Goosegrass (silver crabgrass) Eleusine indica Has a flat rosette of tough stems with a whitish center. Most common on poor, hard-packed soil.Preemergence control bensulide + oxadiazon, or oxadiazon, or pendimethalinLate spring to early summerHerbicides are more effective when watered in following application. Check labels for nontolerant species and cultivars and for intervals until overseeding can take place.
Postemergence control Fenoxaprop-p-ethylEarly summerFenoxaprop-p-ethyl should be applied only when there is adequate moisture and goosegrass is actively growing. This herbicide may temporarily discolor some Kentucky bluegrass cultivars and is less effective if tank-mixed with phenoxy-type herbicides.
Ground Ivy Glechoma hederacea Creeping plant with round scalloped leaves on square stems. Has small, purplish, trumpet-shaped flowers. May form large patches. Greatest nuisance in moist shady areas. Hard to kill.2,4-D + MCPP + dicamba, or 2,4-D + triclopyrEarly spring or fall. Fall applications are most effective if made after first frost.Extremely difficult to kill. Repeat applications will reduce, but may not completely eliminate, this weed.
Hawkweed Heracium spp.2,4-D + dicamba, or 2,4-D + MCPP + dicamba, or MCPA + MCPP + dicambaEarly spring or fallRepeat applications may be necessary. Control may be improved with a wetting agent (check herbicide label to see if a wetting agent is allowed). Thoroughly wet the plant. Accompany with adequate lime and fertilizer treatment.
Henbit Lamium amplexicaule
Mainly an early spring problem, this mint family member has the typical square stems and light purple trumpet-shaped flowers.
2,4-D + dicamba, or 2,4-D + 2,4-DP, or 2,4-D + MCPP + dicamba, or 2,4-D + triclopyrSpringDifficult to control. Treat weeds when young; repeat applications may be necessary.
Knotweed Malva spp. This tough mat-forming plant prefers hard, compacted soil. Has blue-green leaves.2,4-D + MCPP + dicamba, or 2,4-D + triclopyr, or 2,4-D + 2,4-DP, or 2,4-D + 2,4-DP + dicambaSpringExtremely difficult to kill. May require repeat applications.
Nutsedge, Yellow Cyperus esculentus Grass-like weed with shiny, stiff, upright, yellow-green leaves. Grows vigorously in summer, usually in patches. Moisture-loving. Hard to kill.Bentazon or halosulfuronWhen weeds are actively growing in late spring or early summer
2,4-D, or 2,4-D + MCPP + dicamba, or 2,4-D + 2,4-DP + dicamba, or 2,4-D + triclopyr, or MCPA + MCPP + dicambaSpring or fallBest control when weeds are actively growing. Maintain good soil fertility
Purslane Portulaca oleracea An annual succulent with red prostrate stems and yellow flowers.2,4-D + MCPP + dicamba, or 2,4-D + triclopyrWhen actively growingDifficult to kill; repeat applications may be needed.
Sheep Sorrel (red sorrel) Rumex acetosella A hard-to-kill pest, easily identified by its spear- or arrow-shaped leaves and long stringy roots. Thrives in acid or "sour" soil.2,4-D + 2,4-DP + dicamba, or dicamba, or 2,4-D + MCPP + dicamba, or MCPA + MCPP + dicambaSpring, summer, or early fallApply lime and fertilizer as needed.
Shepherd's Purse Capsella bursapastoris Annual weed with triangular, purse-like pods.MCPP, or dicamba, or 2,4-D + MCPP + dicamba, or MCPA + MCPP + dicambaSpring or fallBest control when weeds are actively growing.
Prostrate Spurge Euphorbia supina Has a spreading growth habit, milky sap, and leaves with a purplish spot.Postemergence control: dicamba, or 2,4-D + MCPP + dicamba, or MCPA + MCPP + dicambaWhen weeds are actively growingSpurge is difficult to kill; may require repeat applications.
Preemergence control: pendimethalin, or benefin + trifluralin, or prodiamineEarly to mid-spring
Speedwells:
Common speedwells Veronica officinalis Both perennial and annual kinds may infest lawns. All have creeping stems, opposite leaves, and small blue or white, four-petalled flowers.2,4-D + MCPP + dicambaSpring or summerDifficult to control.
Creeping Veronica filiformis2,4-D + triclopyr, or quincloracMid- to late MayExtremely difficult to control; repeat applications may be necessary.
Corn or rock Veronica arvensisPostemergence control: 2,4-D + MCPP + dicamba,or 2,4-D + triclopyrSpring or summerExtremely difficult to control; repeat applications may be necessary.
Preemergence control: OxidiazonLate summerApply in August before weeds germinate.
Thyme-leaved Veronica serpyllifolia2,4-D + MCPP + dicambaSpringExtremely difficult to control; complete control unlikely. Be sure lime and fertilizer needs are met.
Violets Viola spp. The familiar common violet, with its blue or purple flowers and heart-shaped leaves. Sometimes invades lawns. Hard to kill.2,4-D + 2,4-DP, or 2,4-D + 2,4-DP + dicamba or 2,4-D + triclopyrMayLimited effectiveness; repeat applications usually necessary.
Wild Garlic Allium vineale Wild Onion Allium canadense One of the most troublesome weeds Even "weed-proof" zoysia can't stop it. Grows vigorously in spring and fall, but foliage disappears in summer.2,4-D, or 2,4-D + MCPP + dicamba, or 2,4-D + 2,4-DP + dicambaSpring, when garlic and onions are actively growingRequires treatment annually for several years. Use ester formulation, wet plants thoroughly.
Woodsorrel, Yellow Oxalis spp. Has pale-green, clover-like leaves, and small yellow flowers. Seed capsules resemble tiny cucumbers.2,4-D + 2,4-DP, or 2,4-D + 2,4-DP + dicamba, or 2,4-D + triclopyrSummer or fallDifficult to kill. May require repeat applications.
Yellow Rocket (wintercress) Barbarea vulgaris Biennials with dark green, deeply lobed leaves and yellow flowers with four petals.2,4-D, or 2,4-D + MCPP + dicambaSpringBest control when weeds are actively growing

*All the chemical listed in this publication can be used on home lawns, but some are only available to professionals with a certified applicator’s license.

**Suggestions for specific herbicides are based on product label information and performance in a limited number of research trials. Because herbicide effectiveness can vary with environmental conditions, location, and methods of application, suggestions listed in this table may not completely conform to the turfgrass safety and weed control standards indicated by research trials.

References

Hart, S., D.W. Lycan and J. A. Meade. 2004. Weed Control inHome Lawns. Rutgers Cooperative Research and Extension, FS119.  Revised  August 2003.

Chemical Weed Control, Center for Turfgrass Science, Penn State, College of Agricultural Sciences. http://plantscience.psu.edu/research/centers/turf/extension/factsheets/weed-management/chemical-weed-control

Suggestions for selective control of turfgrass weeds in Pennsylvania, by weed species.  Center for Turfgrass Science, Penn State, College of Agricultural Sciences. http://plantscience.psu.edu/research/centers/turf/extension/factsheets/weed-management/table-4

 

 



Original Publication Date:

Cooperative Extension Education in Agriculture and Home Economics, University of Delaware, Delaware State University and the United States Department of Agriculture cooperating. Distributed in furtherance of Acts of Congress of May 8 and June 30, 1914. It is the policy of the Delaware Cooperative Extension System that no person shall be subjected to discrimination on the grounds of race, color, sex, disability, age, or national origin.

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