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Controlling Broadleaf Weeds in Turf

May 21, 2003

Yellow dandelion flowers are often welcomed by children as harbingers of spring. To turf managers, however, actively growing dandelions and other broadleaf weeds signal the need for control and preventive practices.

Weed invasions can be minimized through proper turfgrass management. Consider use, site, and budget when selecting an appropriate turfgrass. Follow correct selection with appropriate mowing, watering, fertilizing, and cultivating; all can lead to a dense, healthy turf. Reduced weed populations result because weeds have difficulty becoming established in healthy, competitive turf.

In areas where broadleaf weeds are already a problem, mow frequently to prevent seed-head production; and after properly identifying the problem weed species, initiate controls. For help with identification, check out http://www.turf.uiuc.edu. Learning the weed’s life cycle and preferred growing conditions can greatly assist with control efforts. Perhaps growing conditions can be altered to be less favorable. Mechanical removal of weeds by hand-pulling or hoeing can eliminate small numbers of weeds easily. Be sure to remove as much of the root system as possible to reduce regrowth of perennials. Persistance may be needed but will be rewarded.

Proper cultural practices can greatly reduce weed populations. However, if weed problems persist, herbicides can be used.

Postemergence herbicides can provide effective control, and now is an opportune time to apply, as many weeds are actively growing. Individual herbicides or combinations of herbicides are available. Be sure to read, understand, and follow the label directions for proper use of these chemicals. If mishandled or misapplied, these herbicides may damage or kill many desirable ornamental or edible plants in the landscape or nearby garden. Check the label for specifice guidance on where the product can or cannot be applied and for rain-free period (rain-fast) information. Follow these general recommendations when using postemergence broadleaf products.

  1. Apply these herbicides when environmental conditions are appropriate for control.
  2. a. Watch wind speeds to avoid drift. Often, early mornings are less windy than later in the day. A gentle, blowing breeze of 3 to 10 mph is recommended. Be sure the wind is blowing away from sensitive areas.

    b. Apply these herbicides when air temperatures are between 55 degrees and 85 degrees F.

    c. Adequate soil moisture is important to maintain growth and translocation of herbicides throughout the entire weed.

    d. Do not apply when precipitation is expected within 24 hours.

  3. Don’t mow for a few days before or after application, thereby allowing maximum leaf surface for interception and absorption of the herbicides.
  4. When possible, to reduce unnecessary pesticide use, make spot applications rather than treating large areas.
  5. Apply these herbicides to new turfgrass seedlings only after they have been mowed three or four times. Wait at least 30 days after application before seeding into areas treated with postemergence broadleaf herbicides.
  6. Many broadleaf weeds such as dandelion and ground ivy can also be treated effectively during active growth in autumn. Do not ignore treatment during this time when broadleaf weeds are a turf problem. In fact, autumn is an excellent time to apply these herbicides as weeds are busy preparing for winter by moving excess carbohydrates to the roots. This can aid translocation. The cooler temperatures of autumn allow for use of ester formulations because there is less risk of vapor drift. Amine formulations should be used instead when air temperatures are warmer. Finally, cool season turfgrasses are actively growing in autumn and more quickly fill in bare areas left by dying weeds.

In research conducted over several years at the University of Illinois Landscape Horticulture Research Center, several herbicides provided effective postemergence control of common broadleaf weeds such as white clover, dandelions, and plantains. These herbicides are 2,4-D + MCPP + dicamba; triclopyr + clopyralid; and 2,4-D + triclopyr. For additional information regarding other chemical weed controls or other weeds, see the 2003 Commercial Landscape and Turfgrass Pest Management Handbook. Information about common postemergence herbicides follows. Trade names are given as examples only and should not be considered endorsements of any kind.

2,4-D; MCPP (mecoprop); MCPA; and 2,4-DP (dichlorprop): These herbicides are in the phenoxy acid family. In this group, 2,4-D is the oldest and most widely used. It is effective on taprooted weeds such as dandelion and broadleaf plantain; but, by itself, 2,4-D does not control white clover, chickweed, purselane, ground ivy, or violets very well. Ester forms of 2,4-D are recommended for wild garlic and onion control. MCPA is very similar to 2,4-D but does not control the broad spectrum of weeds that 2,4 D controls. If chickweed or white clover is a problem, MCPP is a recommended control. Dichlorprop is combined with other broadleaf herbicides; control of henbit, knotweed, and spurge is usually improved when it is combined with 2,4-D.

dicamba (Banvel, Vanquish): Dicamba, a benzoic acid, works similarly to the phenoxy acid group and is effective against knotweed, purslane, and spurge. It also can be an effective control of ground ivy but does not control buckhorn or broadleaf plantains well. Dicamba is relatively mobile in the soil.

triclopyr (Turflon Ester): Less broad-spectrum than the commonly used combination of 2,4-D + MCPP + dicamba, triclopyr is very active against ground ivy and oxalis.

clopyralid (Lontrel T&O): Also less broad-spectrum than the commonly used combination of 2,4-D + MCPP + dicamba, clopyralid is very active against white clover and thistle. The manufacturer, Dow Agrosciences, has discontinued the allowed use of clopyralid on residential lawns due to residues found in compost this past July. New product labels will include this change. Existing stocks may still be used in this manner, but it is advised that users carefully read and follow label statements concerning the prohibited use of clippings from clopyralid-treated turf as compost.

quinclorac (Drive): An unusual product, as quinclorac is active against white clover, veronica, dandelion, and crabgrass.

clorsulfuron (Corsair): Used by itself or in combination products on Kentucky bluegrass or fine fescues to control a broad spectrum of weeds, it also controls tall fescue.

carfentrazone-ethyl (Speed Zone, Power Zone): With 2,4-D + MCPP + dicamba in Speed Zone; with MCPA + MCPP + dicamba in Power Zone; labeled a “reduced risk” herbicide by EPA; disrupts chlorophyll synthesis; increases speed of activity compared to traditional postemergence broadleaf herbicides.

Many postemergence combination products are manufactured to increase the spectrum of weed control. Included in this group are

2,4-D + MCPP + dicamba (Trimec Classic)

2,4-D + 2,4-DP (Weedone DPC Ester)

2,4-D + MCPP + 2,4-DP (Tri-Ester)

MCPA + MCPP + dicamba (Tri-Power)

MCPA + MCPP + dicamba (Tri-Power)

Several preemergence herbicides can be applied to control broadleaf weeds in turf. It is not too late to use these herbicides for controlling such species as prostrate spurge that require warmer soil temperatures (even up into the low 90s) to germinate. Keep in mind that these herbicides must be applied prior to germination to be effective. Existing weeds can be controlled using the methods previously discussed. General recommendations can be made when using these products in turf.

  1. Conduct any cultivation practices based on label directions; when in doubt, core-aerify or dethatch before herbicide application.
  2. Water following application according to the herbicide label direction.
  3. To lengthen the period of weed control, make a second application of the herbicide at a later date. Follow the specific label directions for rates and timing.
  4. Consult individual preemergence herbicide labels for the specific waiting period between herbicide application and overseeding or reestablishment. Avoid applying a preemergence herbicide immediately before installing sod.

Various preemergence herbicides are available for controlling broadleaf weeds:

dithiopyr (Dimension): According to the label, this herbicide controls chickweed, henbit, purslane, spurges, and yellow woodsorrel when applied before weed emergence.

isoxaben (Gallery): According to the label, this herbicide controls many weeds, including dandelion (see label for recommendations). It has no postemergence activity, so control existing weeds with post emergence spray. Although isoxaban is much more expensive than postemergence herbicides, consider using it where weeds are a persistent problem.

pendimethalin (Pre-M, Pendulum): According to the label, this herbicide controls chickweed, henbit, knotweed, prostrate spurge, purslane, and yellow woodsorrel when applied before weed emergence.

prodiamine (Barricade): According to the label, this herbicide controls common chickweed, henbit, knotweed, prostrate spurge, purslane, and yellow woodsorrel when applied beore weed emergence.

Don’t worry about depriving any children of fond springtime memories of playing the dandelion “do you like butter (boys)” game. They’ll manage. There is no shortage of dandelions in this world. It’s nice that we have several control options.

Author: Tom Voigt Michelle Wiesbrook


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