A weed is defined as a plant out of place, or a plant growing where it is not desired. Weeds compete with turfgrasses for light, water, soil nutrients and space. In a turf, weeds disrupt uniformity and are often considered to be aesthetically unpleasing. With a few exceptions, weeds will not provide year-round vegetative cover. A year-round turf cover is especially beneficial to prevent erosion and runoff, and in areas that might receive moderate to heavy use during the non-growing season. Weeds in athletic fields can adversely affect playability and athlete safety.

Weeds of turf are most often categorized by their life cycle. The most important thing one can learn about a specific weed is its life cycle. Knowledge of the life cycle is valuable when attempting to manage a specific weed because not all strategies are appropriate for all life cycles. Also, the timing of when a specific control strategy is implemented will vary based on a weed’s life cycle. A weed can be a summer annual, winter annual, biennial or perennial (Tables 9 and 10).

Annual weeds

Annual weeds reproduce by seed and complete their life cycle in one year. The annual life cycle is further divided into summer annual weeds and winter annual weeds. Summer annual weeds germinate in spring or early summer, grow vegetatively, flower and produce seed and die in late summer or fall. Examples of summer annual weeds include crabgrass, yellow foxtail, goosegrass, barnyardgrass, ragweed, purslane, spotted spurge, pigweed, carpetweed and prostrate knotweed. Winter annual weeds germinate in late summer and fall. They grow vegetatively and go dormant with the arrival of cold weather. In the spring they continue to grow vegetatively early and then switch to a reproductive phrase during which they flower and produce seed. After flowering, they die with the onset of warm weather. Winter annual weeds can be just as problematic and troublesome as summer annual weeds. Examples of winter annual weeds include shepherd’s-purse, common chickweed, sticky chickweed, annual bluegrass, henbit, pineappleweed, spring whitlowgrass and corn speedwell.

Biennial weeds

Biennial weeds reproduce by seed and complete their life cycle in two years. Biennial weeds germinate in spring to early summer and grow vegetatively forming a leaf rosette at the end of the first growing season. After over-wintering as a rosette, the biennial weed resumes growth, flowers, produces seed and completes the life cycle in the second growing season. Examples of biennial weeds are common mullein, burdock, bull thistle, wild carrot and garlic mustard.

Perennial weeds

Perennial weeds live for three or more years and reproduce by seed and vegetative propagules including roots, rhizomes, stolons, tubers, and bulbs. Dandelion, broadleaf plantain, narrowleaf plantain, broadleaf dock, false dandelion, spotted cat’s ear and fall dandelion are examples of simple perennials and reproduce by seed. Spreading perennials reproduce by seed and vegetative propagules and can form sizable clonal patches in turf. Examples of spreading perennials are quackgrass, red sorrel, creeping woodsorrel, Canada thistle and ground ivy. Other perennials such as wild garlic and star-of-bethlehem arise from bulbs. Yellow nutsedge arises from small tubers called nutlets.

Table 9. Life cycles of common broadleaf turf weeds

Common name	Scientific name	Life cycle
alyssum, hoary	Berteroa incana	perennial
bedstraw, catchweed	Galium aparine	winter annual
bedstraw, smooth	Galium mollugo	perennial
beggarticks, devil’s	Bidens frondosa	summer annual
bittercress	Cardamine hirsuta	winter annual
bittercress, cuckoo	Cardamine pratensis	perennial
bluets	Houstonia caerulea	perennial
buttercup, bulbous	Ranunculus bulbosus	perennial
buttercup, creeping	Ranunculus repens	perennial
carpetweed	Mollugo verticillata	summer annual
carrot, wild	Daucus carota	perennial
cat’s ear	Hypochaeris radicata	perennial
celandine, lesser	Ranunculus ficaria	perennial
chickweed, common	Stellaria media	winter annual
chickweed, mouse-ear	Cerastium vulgatum	perennial
chickweed, sticky	Cerastium viscosum	winter annual
chicory	Cichorium intybus	perennial
cinquefoil, old field	Potentilla simplex	perennial
cinquefoil, silvery	Potentilla argentea	perennial
clearweed	Pilea pumila	summer annual
clover, alsike	Trifolium hybridum	perennial
clover, rabbitfoot	Trifolium arvense	summer annual
clover, red	Trifolium pratense	perennial
clover, white	Trifolium repens	perennial
common lambsquarters	Chenopodium album	summer annual
copper-leaf, rhombic	Acalypha rhomboidea	summer annual
daisy, oxeye	Chrysanthemum leucanthemum	perennial
dandelion	Taraxacum officinale	perennial
dandelion, fall	Leontodon autumnalis	perennial
deadnettle, red	Lamium purpureum	winter annual
deptford pink	Dianthus armeria	perennial
dock, broadleaf	Rumex obtusifolius	perennial
dock, curly	Rumex crispus	perennial
evening primrose, common	Oenothera biennis	biennial
fleabane, annual	Erigeron annuus	winter annual/biennial
fleabane, poor-robin	Erigeron pulchellus	perennial
galinsoga, hairy	Galinsoga ciliata	summer annual
garlic, wild	Allium vineale	perennial
ground ivy	Glechoma hederacea	perennial
groundsel, common	Senecio vulgaris	summer annual
hawksbeard, narrowleaf	Crepis tectorum	summer annual
hawkweed, orange	Hieracium aurantiacum	perennial
hawkweed, yellow	Hieracium pretense	perennial
healall	Prunella vulgaris	perennial
hedge bindweed	Calystegia sepium	perennial
henbit	Lamium amplexicaule	winter annual
horseweed	Conyza canadensis	winter annual
jimsonweed	Datura stramonium	summer annual
knawel	Scleranthus annuus	winter annual
knotweed, prostrate	Polygonum aviculare	summer annual
maiden pink	Dianthus deltoids	perennial
mallow, common	Malva neglecta	annual/biennial
medic, black	Medicago lupulina	annual
moneywort	Lysimachia nummularia	perennial
mouse-ear cress	Arabidopsis thaliana	winter annual
mugwort	Artemisia vulgaris	perennial
nightshade, eastern black	Solanum ptycanthum	summer annual
pearlwort, birdseye	Sagina procumbens	perennial
pepperweed, virginia	Lepidium virginicum	summer or winter annual
pigweed, prostrate	Amaranthus lividus	summer annual
pigweed, redroot	Amaranthus retroflexus	summer annual
pimpernel, scarlet	Anagallis arvensis	summer annual
pineappleweed	Matricaria matricariodes	winter annual
plantain, broadleaf	Plantago major	perennial
plantain, narrowleaf	Plantago lanceolata	perennial
pokeweed, common	Phytolacca americana	perennial
purslane, common	Portulaca oleracea	summer annual
pussytoes, field	Antennaria neglecta	perennial
ragweed, common	Ambrosia artemisiifolia	summer annual
ragweed, giant	Ambrosia trifida	summer annual
rocket, yellow	Barbarea vulgaris	biennial
sandspurry, red	Spergularia rubra	summer annual
shepherd’s-purse	Capsella bursa-pastoris	winter annual
smartweed, ladysthumb	Polygonum persicaria	summer annual
smartweed, Pennsylvania	Polygonum pensylvanicum	summer annual
sorrel, red/sheep	Rumex acetosella	perennial
sowthistle, annual	Sonchus oleraceus	summer annual
sowthistle, perennial	Sonchus arvensis	perennial
sowthistle, spiny	Sonchus asper	summer annual
speedwell, common	Veronica officinalis	perennial
speedwell, corn	Veronica arvensis	winter annual
speedwell, purslane	Veronica peregrina	winter annual
speedwell, thymeleaf	Veronica serpyllifolia	perennial
spurge, spotted	Euphorbia maculata	summer annual
star-of-bethlehem	Ornithogalum umbellatum	perennial
stitchwort	Stellaria graminea	perennial
strawberry, wild	Fragaria virginiana	perennial
thistle, Canada	Cirsium arvense	perennial
thymeleaf sandwort	Arenaria serpyllifolia	winter annual
toadflax, oldfield	Linaria canadensis	summer annual
toadflax, yellow	Linaria vulgaris	perennial
tower mustard	Arabis glabra	biennial
trefoil, birdsfoot	Lotus corniculatus	perennial
velvetleaf	Abutilon theophrasti	summer annual
violet, wild	Viola spp.	perennial
white cockle	Silene alba	perennial
whitlowgrass, spring	Draba verna	winter annual
woodsorrel, creeping	Oxalis corniculata	perennial
yarrow	Achillea millefolium	perennial
yellow woodsorrel	Oxalis stricta	perennial

Table 10. Life cycles of common grass and grass-like turf weeds

Common name	Scientific name	Life cycle
barnyardgrass	Echinochloa crus-galli	summer annual
bentgrass, creeping	Agrostis stolonifera	perennial
bluegrass roughstalk	Poa trivialis	perennial
bluegrass, annual	Poa annua	winter annual/perennial
bluegrass, bulbous	Poa bulbosa	perennial
brome, downy	Bromus tectorum	winter annual
crabgrass, smooth or small	Digitaria ischaemum	summer annual
crabgrass, large or hairy	Digitaria sanguinalis	summer annual
fescue, tall	Festuca arundinacea	perennial
foxtail, giant	Setaria faberi	summer annual
foxtail, yellow	Setaria glauca	summer annual
goosegrass	Eleusine indica	summer annual
lovegrass, purple	Eragrotis spectabilis	perennial
nimblewill	Muhlenbergia schreberi	perennial
nutsedge, yellow	Cyperus esculentus	perennial
orchardgrass	Dactylis glomerata	perennial
panicum, fall	Panicum dichotomiflorum	summer annual
paspalum	Paspalum setaceum	perennial
quackgrass	Elytrigia repens	summer annual
rush, path	Juncus tenuis	perennial
sandbur, longspine	Cenchrus longispinus	summer annual
stiltgrass, Japanese	Microstegium vimineum	summer annual
stinkgrass (lovegrass)	Eragrostis cilianensis	summer annual
timothy	Phleum pratense	perennial
witchgrass	Panicum capillare	summer annual
zoysiagrass	Zoysia japonica	perennial

 

Scouting and monitoring are important components of an effective integrated management program for turf weeds. Monitoring should be done every time a turf manager is on a particular site, in addition to an all-inclusive, in-depth scouting event carried out in late summer or early fall.

The turf manager should use a back and forth or zig-zag pattern when scouting for weeds, being sure to cover all distinctly different and/or known problem areas. Special attention should be given to areas of thin turf and possible causes, as well as newly introduced weeds and historically problematic weeds that are not controlled with the current management program. All weed species present and their respective life cycles should be recorded. Observations can be recorded on a site map or listed on a sheet with location identified. Regular scouting and accurate weed identification enables a turf manager to plan and implement an appropriate management approach and to evaluate the long-term effectiveness of control strategies.

Indicator weeds

There is an old adage that states “Weeds are the result of a poor turf, not the cause of a poor turf”. Weed infestation often suggests that there are one or more underlying factors contributing to poor turf health and vigor. A comprehensive list of all weeds should be developed as a turf manager scouts a specific turf site; however there are certain weed species that should be scrutinized more carefully. These weed species, often referred to as “indicator weeds” or “diagnostic weeds”, are particularly competitive when environmental conditions are not optimal for turfgrass growth. The occurrence of indicator weeds can be used as a starting point in identifying those factors that may contribute to poor turf. Identifying and correcting those factors can tip the competitive balance in favor of the turfgrass while minimizing, and in some cases eliminating, many weed infestations.

Red sorrel and bluets are common inhabitants of acid soils, whereas broadleaf plantain may be more abundant at high soil pH. Crabgrass and many other annual weeds require light for germination and thrive in turf areas that are thin as a result of low fertility. White clover and birdsfoot trefoil are also common in low fertility situations and may indicate the need for fertilization. Prostrate knotweed, goosegrass, pineappleweed and path rush commonly occur where the soil has become compacted. Excessive irrigation and/or poorly drained soils may result in an increase in the occurrence of algae, moss, annual bluegrass, creeping bentgrass and yellow nutsedge. Some weeds such as ground ivy, common speedwell and moss are able to thrive in shaded conditions.

Turf managers should not assume that just because these weeds are present that a specific problem exists. For example, red sorrel can grow at high pH and ground ivy may persist in turf areas that receive full sun. While the use of “indicator weeds” is not a fool proof method, it can be a valuable tool in the assessment of potential problems at a turf site.

Cultural practices are a vital component within an effective management program for turf weeds. Successfully executed cultural practices can result in a healthier, denser turf which increases the overall competitive nature of the stand and decreases the severity of many weed infestations. Some weed infestations can be significantly reduced or even eliminated with the use of appropriate and well-timed cultural practices.

Mowing

Many weeds require light for germination and establishment. Increasing the mowing height within the range for the particular species or mix of species present will result in a decrease in the amount of light reaching the soil surface and can reduce weed germination and establishment. This is particularly important in the spring and early summer during the peak germination period of annual grassy weeds. Decreasing the height of cut and collecting clippings that contain seedheads during the late summer and early fall can be effective in reducing the amount of viable seed that is added to the weed seed bank.

Fertility

Fertility, as with mowing height, can play a major role in the reducing the amount of light that penetrates the turf canopy and reaches the soil surface. Fertilization programs should supply adequate and balanced nutrition to yield a dense turf. Avoid high levels of fertility during the summer months when cool-season turfgrasses are less competitive. If heavy summer weed pressure has thinned turf, an application of fertilizer in late summer or early fall will support turf recovery. Fertilization after herbicide applications can aid in the filling of canopy voids left by dying weeds.

Aeration

Compaction is a major contributor to thin turf and the encroachment of weeds. An effective aeration program will alleviate compaction and increase overall turf health and density. However, aeration methods that bring soil to the surface can reposition weed seeds, which were once too deep to germinate, to a location where germination and establishment are favored. The alleviation of compaction in conjunction with overseeding of desirable grasses can reduce and in some cases eliminate weeds such as goosegrass, pathrush, pineappleweed and prostrate knotweed.

Irrigation

Many annual weeds, including crabgrass, are warm-season species. Warm-season species are capable of growing very well during the hot, dry periods characteristic of summer. Turfgrass species utilized in the northeast are cool-season species and, without adequate moisture from rainfall or irrigation, become dormant during the summer. During periods when the growth of cool-season turfgrass species has slowed or ceased as a result of low soil moisture and high temperatures, warm-season annual weeds become very competitive in otherwise healthy, dense turf. If some weed encroachment is not acceptable, irrigation should be applied in the absence of summer rainfall to maintain turf growth and prevent summer dormancy. Special attention should be focused on areas that are prone to drought including elevated areas, south and southwest facing slopes and areas adjacent to hardscapes such as sidewalks and driveways. If there is annual weed pressure and the turf at a site is going to be allowed to go dormant during the summer months, the option also exists to apply a preemergence herbicide in the spring. If turf has thinned due to drought dormancy, overseeding with desirable turfgrass species should be done in late summer/early fall when cooler temperatures and rainfall return.

The over-watering of turf areas can also contribute to weed encroachment. Weeds such as annual bluegrass, creeping bentgrass, and yellow nutsedge can be more problematic on over-irrigated sites. On poorly-drained sites, the installation of a drainage system may be warranted to decrease naturally-existing excessive soil moisture.

Turf Renovation and Establishment

Turf renovation and establishment projects carried out in the spring and early summer without the use of a preemergence herbicide fail more often than not due to annual weed pressure. Summer annual weed pressure is minimal when turf renovation and establishment is initiated in the late summer and early fall. Warm-season annual weeds that germinate later in the season seldom reach a size that deters turf establishment and die with the onset of cold weather. Special attention should be paid to winter annual weed encroachment in such areas, however.

When planning a turf renovation, choose turfgrass species and cultivars that are best suited for the site conditions and expected turf use. Aggressive cultivars should be considered when available. Encourage rapid establishment by providing adequate fertility at seeding. Maintain good soil moisture during the germination and early establishment period. Overseeding can be a valuable tool in restoring sites where turf thinning has resulted from insufficient annual weed control. Openings in the turf as a result of insect damage, diseases and excessive wear are prone to weed encroachment. Overseeding is frequently useful to repair such damage and regain turf density.

In turf management, the two most basic categories of herbicides are preemergence and postemergence. Preemergence materials are applied preventively, that is prior to germination, to control weeds that have not yet appeared. Postemergence materials are applied to existing, actively growing weeds.  Some herbicides have both preemergence and postemergence activity. With such materials, appropriate application timing can be dictated by the target weed(s), distinct characteristics of the herbicide, or specific management goals.

Herbicides can be more finely categorized into chemical classes, which indicate the mode or mechanism of action of each compound. The particular mode of action influences whether a material is effective against broadleaf weeds, grassy weeds, or a more specific collection of species. Many individual modes of action offer selective control of weeds within desirable turf, while others provide non-selective control more appropriate for spot treatment and renovation situations.

Refer to Table 12 below to cross reference trade names with active ingredients.

Table 11. Characteristics of turf herbicide active ingredients registered for use in Massachusetts.

amicarbazone Chemical class Mode of action Application timing triaolinone inhibits photosynthesis postemergence Controls annual bluegrass, crabgrass, bittercress, carpetweed, henbit, field pennycress, common chickweed, sticky chickweed, Virgina pepperweed, purslane, shepherd’s-purse, spurge, and oldfield toadflax.

benefin Chemical class Mode of action Application timing dinitroaniline interferes with cell division preemergence Controls crabgrass, goosegrass, annual bluegrass, yellow foxtail and many annual broadleaf weeds.

bensulide Chemical class Mode of action Application timing organophosphate interferes with cell division and inhibits rooting. preemergence Controls annual bluegrass, crabgrass, goosegrass, henbit, lambsquarters, and yellow foxtail. Provides excellent control of annual bluegrass. Strongly adsorbed to soil, potential for leaching is very low.

bentazon Chemical class Mode of action Application timing benzothiadiazole inhibits photosynthesis, causes cell membrane destruction postemergence Controls primarily yellow nutsedge; will provide control of broadleaf weeds including Canada thistle, groundsel, ladysthumb, lambquarters, Pennsylvania smartweed, purslane, shepard’s purse and yellow woodsorrel. Controls primarily yellow nutsedge; will provide control of broadleaf weeds including Canada thistle, groundsel, ladysthumb, lambquarters, Pennsylvania smartweed, purslane, shepard’s purse and yellow woodsorrel. Contact herbicide. Some temporary turf discoloration may occur. The addition of a surfactant is required for application. Bentazon is regulated under the Public Drinking Water Supply Protection Regulations in MA, see the Pesticide Regulations section of this guide for details.

bispyribac-sodium Chemical class Mode of action Application timing pyrimidinyloxybenoic inhibition of amino acid synthesis postemergence Controls annual bluegrass and roughstalk bluegrass in creeping bentgrass and perennial ryegrass, also broadleaf plantain, common chickweed, dandelion, henbit, narrowleaf plantain, white clover and yellow woodsorrel. May injure Kentucky bluegrass, especially some cultivars. Labeled for use only on golf courses and sod fields.

carfentrazone Chemical class Mode of action Application timing protox inhibitor inhibits chlorophyll production, results in rapid destruction of cell membranes postemergence Controls a wide range of broadleaf weeds. Often formulated in pre-mixed combinations with other broadleaf herbicides. Does not provide good control of perennial broadleaves when applied alone. Provides good moss control. Does not persist in soil and has no leaching potential.

chlorsulfuron Chemical class Mode of action Application timing sulfonylurea inhibition of amino acid synthesis postemergence Controls tall fescue, annual ryegrass and perennial ryegrass in Kentucky bluegrass, fine fescue and bentgrass; also buttercup, cinquefoil, common chickweed, common mallow, henbit, mouse-ear chickweed, pineappleweed, prostrate knotweed, purslane, shepards-purse, white clover, wild garlic and wild violet.

clopyralid Chemical class Mode of action Application timing pyridine disrupts growth by mimicking naturally occurring plant hormones. postemergence Broad spectrum; controls many broadleaves, particularly effective on members of the aster family (dandelion and hawkweed) and bean family (clover, black medic and birdsfoot trefoil). Translocated within the plant. Herbicide products that contain clopyralid are Restricted Use on residential turf. Turf clippings from treated areas should not be collected for mulching and composting or sent to a recycling facility. Use caution near ornamentals, including aster, daisy, coneflower, liatris, redbud, and honeylocust. Clopyralid is weakly adsorbed to soil and has a moderate leaching potential.

corn gluten meal Chemical class Mode of action Application timing not classified inhibition of root growth at germination. preemergence Labeled for the control of crabgrass species. Corn gluten meal is a by-product of the wet-milling of corn grain for the production of corn starch and corn syrup. Because of its high protein content (about 60% by weight), its historic use has been as an animal feed. Its associated nitrogen concentration of about 9 to 10% N makes it a fertilizer. The carrier of the nitrogen is the proteinaceous fraction of the corn grain; several dipeptides in this fraction comprise the active ingredient that imparts some preemergence herbicidal activity. Research suggests that the herbicidal activity is greater in dry environments than in areas where soil moisture for plant growth is adequate. Product application rates for turf are 10 to 20 lbs of corn gluten meal per 1000 ft2 applied twice a year (equal to approximately 2 to 4 lbs of N per 1000 ft2 per year) with some products suggesting higher rates. Studies conducted at the University of Massachusetts indicate that crabgrass control using corn gluten provided no advantage over maintaining a properly fertilized lawn regardless of whether the fertilizer material used was organic or synthetic. Corn gluten is considered to be organic.

dicamba Chemical class Mode of action Application timing benzoic acid disrupts growth by mimicking naturally occurring plant hormones. postemergence Controls many broadleaf weeds, especially red sorrel, dandelion, violets, plantains, chickweed, ground ivy, buttercup and woodsorrel. Formulated alone and in premixed combinations with other broadleaf herbicides. Susceptible weeds curl and twist soon after application. Drift to desirable plants, particularly flowers, ornamentals, and other broadleaf plants should be prevented. Dicamba leaches readily into the soil and is soil active, therefore applications within the drip line of trees should be avoided.

dimethenamid Chemical class Mode of action Application timing chloroacetanilide/chloroacetamide inhibits very long chain fatty acid synthesis preemergence Controls annual bluegrass, crabgrass, downy brome, yellow foxtail, fall panicum, sandbur, bittercress, carpetweed, lambsquarters, pigweed, puslane, common ragweed, shepherd’s-purse, spurge, willowherb, kyllinga and yellow nutsedge. Dimethenamid is regulated under the Public Drinking Water Supply Protection Regulations in MA, see the Pesticide Regulations section of this guide for details.

dithiopyr Chemical class Mode of action Application timing pyridine inhibits cell division. preemergence Controls annual grasses, including annual bluegrass, barnyardgrass, crabgrass, downy brome, yellow foxtail and sandbur. Also provides preemergence control of several broadleaf weeds including bittercress, carpetweed, henbit, black medic, pineappleweed, purslane, shepard’s-purse, corn speedwell, spurge, yellow woodsorrel and creeping woodsorrel. Enters the plant through shoots and roots. Also provides early postemergence crabgrass control when applied before the 3-leaf growth stage.

ethofumesate Chemical class Mode of action Application timing not classified unkown, evidence suggests inhibition of leaf wax formation. preemergence and postemergence Utilized primarily in turf for postemergence control of annual bluegrass. Absorbed by emerging roots and shoots, and is translocated to leaves. Postemergence applications are somewhat poorly absorbed by leaves with thick, well-developed cuticles. Also provides preemergence control of barnyardgrass, common chickweed, crabgrass, purslane and yellow foxtail, and some yellow nutsedge suppression. Ethofumesate is not prone to leaching.

fenoxaprop-ethyl Chemical class Mode of action Application timing aryloxyphenoxyprionate inhibits biosynthesis of fatty acids in sensitive plants postemergence Controls annual grassy weeds, especially large and smooth crabgrass, goosegrass, barnyardgrass, yellow foxtail, sandbur and Japanese stiltgrass. Application rate depends on weed growth stage. Some broadleaf herbicides when tank-mixed with or applied within a certain period of time can reduce the efficacy of fenoxprop as a result of herbicide antagonism. Can be tank-mixed with preemergence crabgrass herbicides to obtain residual control. Drought stress can significantly reduce efficacy. No soil activity.

ferric-HEDTA Chemical class Mode of action Application timing not classified iron toxicity postemergence Ferric-HEDTA is a selective broadleaf herbicide. It is effective at cooler temperatures, rain-fast in a short period of time and results can be seen in as little as 24 to 48 hours. Ferric-HEDTA is quickly absorbed by the leaf tissue and transported down to the root. The leaf tissue turns black or brown and death the of the weed follows.

forasulam Chemical class Mode of action Application timing sulfonanalide inhibits biosynthesis of certain essential amino acids postemergence Controls bedstraw, common chickweed, mouse-ear chickweed, white clover, dandelion, dandelion, fleabane, groundsel, prostrate knotweed, shepherd’s-purse and spurge.

fluroxypyr Chemical class Mode of action Application timing pyridine disrupts growth by mimicking naturally occurring plant hormones. postemergence Broad-spectrum material, especially effective for chickweed, cinquefoil, creeping woodsorrel, dandelion, ground ivy, henbit, plantain, purslane, white clover, wild strawberry, and yellow woodsorrel. Either formulated alone and in pre-mixed combinations with other broadleaf herbicides. Absorbed by roots and shoots and is strongly translocated within the plant. Induces an epinastic (leaf curling) response and death occurs in days or weeks.

glufosinate-ammonium Chemical class Mode of action Application timing not classified causes metabolic changes that disrupt photosynthesis. postemergence Glufosinate-ammonium is a non-selective herbicide. Not translocated. Often poor to fair control of some perennial weeds. No soil activity.

glyphosate Chemical class Mode of action Application timing phosphonoglycine inhibits biosynthesis of certain essential amino acids postemergence Glyphosate is a non-selective herbicide. Strongly translocated and therefore very effective for perennial weeds. Symptoms include yellowing, starting with the youngest plant tissue, and progressing toward the oldest. Binds strongly to soil and does not leach. Glyphosate is not soil active.

halosulfuron Chemical class Mode of action Application timing sulfonylurea inhibits biosynthesis of certain essential amino acids postemergence Halosulfuron is utilized in cool-season turf primarily for the control of yellow nutsedge. Yellow nutsedge is best treated in the three- to eight-leaf stage of growth. The addition of a non-ionic surfactant is required. Halosulfuron is degraded by microbial activity in the soil and has a low potential for leaching.

isoxaben Chemical class Mode of action Application timing amide inhibits the biosynthesis of cellulose, disrupts root and hypocotyl development. preemergence Controls a wide range of broadleaf weeds including black medic, carpetweed, dandelion, henbit, plantain, purslane, red sorrel, spurge, white clover, and yellow woodsorrel. The only compound available exclusively for preemergence control of broadleaf weeds in cool-season turf.

mesotrione Chemical class Mode of action Application timing triketone disrupts carotenoid synthesis. preemergence and postemergence When applied postemergence, mesotrione controls many broadleaf weeds including broadleaf plantain, carpetweed, common chickweed, clover, henbit, horseweed, purslane, purslane speedwell and yellow woodsorrel. Will provide postemergence control of creeping bentgrass, nimblewill, and yellow nutsedge as well. Also indicated for preemergence control of barnyardgrass, crabgrass, yellow foxtail and broadleaf annual weeds. Can be applied at the time of cool-season turf establishment for preemergence control. Symptoms in susceptible weeds include bleaching followed by necrosis. Mesotrione is a synthetic analogue of the alleochemical leptospermone, which is produced by the roots of the “bottle brush” plant (Callistemon citrinus). Classified as a Reduced Risk pesticide by the US Environmental Protection Agency (EPA), for information visit https://www.epa.gov/.

oxadiazon Chemical class Mode of action Application timing protox inhibitor inhibits chlorophyll production, results in rapid destruction of cell membranes. preemergence Primarily controls annual grasses (barnyardgrass, crabgrass and goosegrass) but also controls several broadleaf weeds (bittercress, carpetweed, smartweed, spurge, yellow woodsorrel). Strongly adsorbed by soil colloids and therefore is not prone to leaching.

pendimethalin Chemical class Mode of action Application timing dinitroaniline interferes with cell division preemergence Primarily used for preemergence control of crabgrass and other annual grasses including barnyardgrass, annual bluegrass, yellow foxtail, goosegrass and sandbur.  Also controls several broadleaf weeds including carpetweed, common chickweed, henbit, prostrate knotweed, purslane, spurge and yellow woodsorrel. Pendimethalin is not prone to leaching

penoxsulam Chemical class Mode of action Application timing sulfonamide inhibits biosynthesis of certain essential amino acids. postemergence Controls bittercress, broadleaf plantain, chickweed, dandelion, ground ivy, white clover and yellow wood sorrel. Formulated alone and in combination with other selective herbicides on fertilizers and straight granules. Accepted for review and registration under the Reduced Risk Pesticide Initiative of the US Environmental Protection Agency (EPA), for information visit https://www.epa.gov/.

phenoxy herbicides (2,4-D, 2,4-DP/dichlorprop, MCPA, MCPP/mecoprop) Chemical class Mode of action Application timing growth regulator disrupt growth by mimicking naturally occurring plant hormones. postemergence The phenoxy herbicides control a wide range of broadleaf weeds. Systemic herbicides, but relatively slow acting. General symptoms on susceptible weeds include the twisting and curling of leaves and stems soon after application. Avoid application in hot weather. Products containing 20% or more 2, 4-D are classified as Restricted Use in Massachusetts. MCPA is regulated under the Public Drinking Water Supply Protection Regulations in MA, see the Pesticide Regulations section of this guide for details.

prodiamine Chemical class Mode of action Application timing dinitroaniline interferes with cell division. preemergence Provides preemergence control of crabgrass, goosegrass, annual bluegrass and other annual grasses. Also controls several broadleaf weeds including carpetweed, chickweed, henbit, purslane, spurge and yellow woodsorrel. Low water solubility and is strongly adsorbed to soil, therefore not prone to leaching.

pyraflufen-ethyl Chemical class Mode of action Application timing phenylpyrazole inhibits chlorophyll production, results in rapid destruction of cell membranes. postemergence Controls carpetweed, chickweed, curly dock, dandelion, pineappleweed, purple deadnettle, purslane, round mallow, smartweed and spurge. Contact herbicide. Formulated alone and in premixed combinations with other broadleaf herbicides.

quinclorac Chemical class Mode of action Application timing quinoline carboxylic acid unknown, thought to inhibit cell wall biosynthesis and mimic natural plant hormones. preemergence and postemergence When applied postemergence, provides control of crabgrass, yellow foxtail, barnyardgrass, white clover, black medic, dandelion and speedwell. Also provides preemergence control of crabgrass and other annual grasses. Does not control goosegrass. Absorbed by foliage and roots and is translocated throughout the plant. Formulated alone and in premixed combinations with other broadleaf herbicides. Postemergence treatments require addition of a methylated seed oil, crop oil concentrate or high quality surfactant for best control. Can be used before or after seeding or overseeding of cool-season turfgrasses for the control of crabgrass and other annual grasses. This compound should be used to control crabgrass before the 2-tiller and after the 5-tiller stage of growth.

siduron Chemical class Mode of action Application timing substituted urea root growth inhibitor; disrupts cell division. preemergence Controls barnyardgrass, crabgrass, downy brome, and yellow foxtail. Does not control annual bluegrass, chickweed, clover, goosegrass and plantain. Either formulated alone or on turf starter fertilizers. Unlike many other preemergence herbicides, siduron can be applied at time of seeding, on seedling turf and on sod to be harvested.

sulfentrazone Chemical class Mode of action Application timing protox inhibitor inhibits chlorophyll production, results in rapid destruction of cell membranes. preemergence and postemergence Provides postemergence control of broadleaf weeds including carpetweed, common chickweed, mouse-ear chickweed, dandelion, henbit, lambquarters, narrowleaf plantain, Pennsylvania smartweed, purslane, spurge, star-of-bethelem, speedwell, yellow woodsorrel and creeping woodsorrel. Can be used to control or suppress yellow nutsedge and kyllinga. Formulated alone and in premixed combinations with other broadleaf herbicides. Sulfentrazone is regulated under the Public Drinking Water Supply Protection Regulations in MA, see the Pesticide Regulations section of this guide for details.

topramezone Chemical class Mode of action Application timing pyrazolones disrupts carotenoid synthesis. postemergence Provides effective control of barnyardgrass, large and smooth crabgrass, yellow foxtail,  fall panicum and Japanese stiltgrass. Very effective on goosegrass.

triclopyr Chemical class Mode of action Application timing pyridine disrupts growth by mimicking naturally occurring plant hormones. postemergence Provides effective control of poison ivy, ground ivy, wild violets, and other difficult-to-control perennial weeds. Absorbed by roots and shoots and readily translocated throughout the plant. Formulated alone and in premixed combinations with other broadleaf herbicides. The potential for leaching decreases with increasing soil organic matter and when conditions are favorable for soil microbial activity.

Table 12. Common herbicide products and their active ingredients

Herbicide product	Active ingredient(s)
Acclaim Extra	fenoxaprop-p-ethyl
Armor Tech CGC (40 & 40WP)	dithiopyr
Armor Tech Quin Pro 75DF	quinclorac
Balan 2.5G	benefin
Barricade (4FL, 65WG, on-fertilizer formulations)	prodiamine
Basagran T&O	bentazon
Bensumec 4LF	bensulide
Calvalcade PQ	prodiamine and quinclorac
Cavalcade 65WDG	prodiamine
Defendor	florasulam
Dimension (2EW, EC, Ultra 40WP, on-fertilizer formulations)	dithiopyr
Dismiss	sulfentrazone
Drive (75DF, XLR8)	quinclorac
Echelon 4SC	prodiamine and sulfentrazone
Eject 75DF	quinclorac
Fiesta	ferric HEDTA
Finale	glufosinate
Gallery	isoxaben
Guardrail 65WDG	prodiamine
Halosulfuron Pro	halosulfuron
Jewel	oxadiazon
Kade 65 WDG	prodiamine
Knighthawk	prodiamine
Manage	halosulfuron
Pendulum (2G, 3.3EC, AquaCap)	pendimethalin
PoaConstrictor	ethofumesate
Pre-M (3.3EC, Aqua-Cap, on-fertilizer formulations)	pendimethalin
Pre-San Granular (7G, 12.5G)	bensulide
PrimeraOne Prodiamine 65WDG	prodiamine
PrimeraOne Quinclorac 75DF	quinclorac
PrimeraOne Prodiamine 65WDG	prodiamine
Proclipse 65WDG	prodiamine
Prograss	ethofumesate
Prograss SC	ethofumesate
Pylex	topramezone
Quali-Pro Dithiopyr 40WSB	dithiopyr
Quali-Pro Prodiamine 65WDG	prodiamine
Quali-Pro Quinclorac 75DF	quinclorac
Quin Pro	quinclorac
Resolute (4L, 65WDG)	prodiamine
Resolute (65WG, 4L)	prodiamine
Ronstar (50WSP, FLO, G)	oxadiazon
Ronstar G	oxadiazon
Scythe	pelargonic acid
SedgeHammer	halosulfuron
SedgeHammer+	halosulfuron
Stonewall 65WDG	prodiamine
Stonewall RQ	prodiamine and quinclorac
Team (2G, Pro)	benefin and trifluralin
Tenacity	mesotrione
Tower	dimethanamid
Tupersan	siduron
Velocity SG	bispyribac-sodium
Xonerate	amicarbazone

 

1. Crabgrass and other annual grassy weeds

   The first step in managing crabgrass and other annual grassy weeds, including yellow foxtail and goosegrass, is to insure that the cultural practices previously mentioned in this section are being completed on a routine basis. Fundamental cultural practices including mowing, fertilization, irrigation, and aeration when done correctly can significantly decrease annual grassy weed infestations. Cultural practices alone will seldom control crabgrass and other annual grassy weeds completely and there is commonly a need for herbicides to produce results that are commercially acceptable. An effective crabgrass management program utilizes a preemergence herbicide, followed by a postemergence herbicide as needed in the case of less than acceptable preemergence performance or the need to control “escapes”. With the exception of sites in which there are low populations of crabgrass and other annual grasses, postemergence herbicides should not be relied on as the sole control measure. In some situations, preemergence application can be split with 50% of the use rate being applied during the normal application window and the remaining 50% applied 4 to 6 weeks later.
   1. Preemergence materials
      Preemergence herbicides for the control of crabgrass and other annual grasses are applied in early spring. Applications in most areas of Massachusetts should be completed before Forsythia flowers drop or by approximately the first week in May, depending on prevailing weather conditions. Preemergence herbicides are available in sprayable and on-fertilizer formulations. These products need to be watered in to be activated and with the exception of very few materials (e.g. siduron, mesotrione), reseeding of turf cannot be done for three to four months after application. Refer to the product label for specific instructions in regard to safe reseeding intervals. Many annual broadleaf weeds can also be managed with preemergence herbicides.
       

      Active Ingredient	Trade Name(s)	Comments
      benefin	Balan 2.5G, Team 2G (combination with trifluralin), on-fertilizer formulations
      bensulide	Bensumec 4LF, Pre-San Granular (7G, 12.5G), on-fertilizer formulations
      corn gluten meal	Many formulations available	Corn gluten products are 9-10% N by weight and should be factored into fertility program.
      dithiopyr	Armortech CGC 40, Crab and Spurge Preventer, Dimension (2EW, EC, Ultra 2SC, Ultra 40WP, Ultra WSP), Dynamo 40WSP, Lifeguard, Quali-Pro Dithiopyr 40WSB, on-fertilizer formulations
      dimethenamid	Tower
      mesotrione	Tenacity	Can be used at the time of seeding or overseeding of cool-season turf.
      oxadiazon	Ronstar (50WSP, FLO, G) Quali-Pro Oxadiazon 2G, Starfighter (3.17F, 2G), on-fertilizer formulations
      pendimethalin	Pendulum (2G, 3.3EC, AquaCap), Pre-M 3.3EC, on-fertilizer formulations (Halts, Pre-M)
      prodiamine	Barricade (4FL, 65WG), Cavalcade 65WDG, Echelon 45SC (combination with sulfentrazone, Guardrail 65WDG, Knighthawk, Quaili-Pro Prodiamine 65WDG, Stonewall 65WDG, Primeone Prodiamine 65WDG, Proclipse (4F, 65WDG), Resolute 65WDG, on-fertilizer formulations
      quinclorac	Armortech Quin Pro 75DF, Eject 75DF, Drive (75DF, XLR8), PrimeraOne Quinclorac 75DF, Quali-Pro Quinclorac 75DF	Can be used before or after seeding or over-seeding of cool-season turfgrasses for the control of crabgrass and other annual grasses.
      siduron	Tupersan (50WP, 4.6G), on-fertilizer formulations	Can be used at the time of seeding or overseeding of cool-season turf.

   2. Postemergence materials
      Another strategy for managing crabgrass and other annual grasses is the use of postemergence herbicides. The most effective and economical control programs use a preemergence herbicide and a postemergence herbicide, if needed, to clean-up weed escapes.
       

      Active Ingredient	Trade Name(s)	Comments
      fenoxaprop-ethyl	Acclaim Extra
      dithiopyr	Armortech CGC 40, Crab and Spurge Preventer, Dimension (2EW, EC, Ultra 2SC, Ultra 40WP, Ultra WSP), Dynamo 40WSP, Lifeguard, Quali-Pro Dithiopyr 40WSB, on-fertilizer formulations
      quinclorac	Armortech Quin Pro 75DF, Eject 75DF, Drive (75DF, XLR8), PrimeraOne Quinclorac 75DF, Quali-Pro Quinclorac 75DF, plus several combinations with broadleaf herbicides.	Can be used before or after seeding or over-seeding of cool-season turfgrasses for the control of crabgrass and other annual grasses.
      mesotrione	Tenacity

2. Broadleaf Weeds

   1. Preemergence materials
      Preemergence herbicide application for the control of broadleaf weeds in turf is not a common practice. Most often these weeds are controlled with postemergence broadleaf herbicides discussed in section 2B below. There are, however, some situations in which preemergence herbicides can be incorporated into an effective weed management program. Preemergence herbicides used for the control of crabgrass and other annual grass weeds (section 1A above) will effectively control many annual broadleaf weeds. The herbicides isoxaben and mesotrione are labeled for the preemergence control of many annual and perennial broadleaf weeds. These products need to be applied before weeds germinate.
       

      Active Ingredient	Trade Name(s)	Comments
      isoxaben	Gallery	The only material available exclusively for preemergence control of broadleaf weeds in cool-season turf.
      benefin, bensulide, dithiopyr, mesotrione, oxadiazon, pendimethalin, prodiamine, siduron	Several preemergence herbicides used for the control of crabgrass and other annual grass weeds will effectively control many annual broadleaf weeds – see Section IA above.

   2. Postemergence
      Annual and perennial broadleaf turf weeds can be managed with postemergence herbicides. Sprayable formulations are the most common but granular and on-fertilizer formulations are also available. Broadleaf weeds can be treated at any time of the growing season as long as weeds and cool-season turfgrasses are actively growing. Applications are best done in the fall and spring, avoiding periods when cool-season turfgrasses are heat and/or drought stressed. Winter annual broadleaf weeds that occur in late summer and fall turf seedlings can be controlled with broadleaf herbicides after the turf has received a minimum of three mowings. Postemergence broadleaf herbicides include the phenoxy herbicides (2,4-D, 2,4-DP/dichlorprop, MCPA, MCPP/mecoprop), carfentrazone, clopyralid, dicamba, fluroxapyr, quinclorac, penoxsulam, pyraflufen-ethyl, sulfentrazone and triclopyr. Broadleaf herbicide products are formulated as a single herbicide or in combinations of two, three or four herbicides, as summarized in Table 13:
      
      Table 13. Active ingredients in commercially-available postemergence herbicide products.
      Click to download Table 13

3. Yellow Nutsedge

   Yellow nutsedge is one of the most difficult to control weeds in turf. Applications for yellow nutsedge should be made soon after spring and early summer emergence with application completed before the summer solstice. Heavy infestations can be treated with glyphosate.

   Active Ingredient	Trade Name(s)	Comments
   bentazon	Basagran T&O, Nutgrass Nihilator	2 applications commonly needed. Bentazon is regulated under the Public Drinking Water Supply Protection Regulations in MA, see the Pesticide Regulations section of this guide for details.
   dimethanamid	Tower	Preemergence material for application where perennial stands of yellow nutsedge are known to exist.
   halosulfuron	Manage, SedgeHammer, Halosulfuron Pro	Addition of a non-ionic surfactant is required.
   mesotrione	Tenacity
   sulfentrazone	Dismiss, Q4 Plus, Surge, Eschelon 4SC (combination with pendimethalin)	Sulfentrazone is regulated under the Public Drinking Water Supply Protection Regulations in MA, see the Pesticide Regulations section of this guide for details.

4. Annual Bluegrass

   Annual bluegrass is a winter annual with perennial biotypes being common in certain turf situations. Annual bluegrass germination occurs primarily in very late summer and fall. Ethofumesate and bispyribac-sodium are labeled for selective postemergence control in certain cool season turfgrass species. Annual bluegrass can be controlled with preemergence crabgrass herbicides when those materials are applied in late summer and fall before germination.

   Active Ingredient	Trade Name(s)	Comments
   ethofumesate	Prograss, Poa Constrictor	Applications are best made in the fall and 2 to 3 repeat applications at 3 to 4 week intervals may be needed.
   bispyribac-sodium	Velocity SP, Velocity SG	Labeled for use only on golf courses and sod fields.
   benefin, bensulide, dithiopyr, mesotrione (suppresses growth), prodiamine, pendimethalin	Several preemergence herbicides used for the control of crabgrass and other annual grass weeds will effectively control or suppress annual bluegrass – see Section IA above.

5. Non-selective herbicides for turf renovation

   Non-selective herbicides are used to kill existing turfgrass, weeds and other vegetation before turf renovation. Using any of these herbicides for the spot-treatment of existing weeds in established turf is not recommended as turf injury or death will occur in the treated areas. The herbicide glyphosate is strongly translocated and therefore is the best option of the non-selective herbicides for use prior to turf renovation. Glufosinate is not as strongly translocated as glyphosate and therefore can be weak on perennial weeds. Glufosinate can be used when the weed population is comprised of only annual weeds. Pelargonic acid, acetic acid, citric acid, clove oil and d-limonene are contact in nature and will not control perennial weeds making them inappropriate to use in turf renovation.

   Active Ingredient	Trade Name(s)	Comments
   glufosinate	Finale	May be weak on perennial weeds.
   glyphosate	Roundup Pro Max, GlyphoMate 41, many others
   pelargonic acid	Scythe	Not appropriate for turf renovation.
   acetic acid, citric acid, clove oil, d-limonene	various materials formulated alone or in combination	Not appropriate for turf renovation.

6. Selective perennial grass control

   Turf areas are often plagued by undesirables: cool-season and warm-season perennial grasses that disrupt uniformity and can result in an unacceptable turf. These grasses include creeping bentgrass, nimblewill, orchardgrass, paspalum, purpletop, quackgrass, tall fescue, timothy and zoysiagrass. A few herbicides are labeled for the selective control of certain grasses, however, most often the area is best treated with glyphosate and reestablished by seeding or sodding.
    

   Active Ingredient	Trade Name(s)	Comments
   chlorosulfuron	Corsair	Controls tall fescue, perennial ryegrass and annual ryegrass.
   glyphosate	Roundup Pro Max, GlyphoMate 41, many others	Spot or broadcast treatment on all species.
   mesotrione	Tenacity	Controls creeping bentgrass and nimblewill.
   metsulfuron	Manor, MSM	Controls perennial ryegrass.