Issue 11, September 21, 2022

Fall Is Good Time for Broadleaf Weed Control in Turf

Fall Is Good Time for Broadleaf Weed Control in Turf

With the long hot days of summer coming to a close, we can look forward to cooler days in the fall. If broadleaf weeds populations are unacceptably high in turf areas you own or manage, it’s time to plan your attack.  Fall is the ideal time to control broadleaf weeds in turfgrass as winter annual weeds and cool season perennial weeds will soon be preparing for the long, cold months ahead.  

September really is an excellent time for overseeding and establishment as its temperatures are more conducive to good turf growth. With cool season lawns starting to green up again, core aerification can be used to alleviate compaction. Those areas in the lawn that are primarily broadleaf plantain and knotweed may be prime target candidates for core aerification. With cooler temperatures, comes germination of cool-season annual weeds such as chickweed and henbit. Take a scouting trip to see what is growing where.

Proper turfgrass management is the first step in minimizing weed invasions. When selecting an appropriate turfgrass, consider use, site, and budget. Then follow with appropriate mowing, watering, fertilizing, and cultivating; all can lead to a dense, healthy turf. Weeds have difficulty establishing themselves in healthy, competitive turf.  Therefore, weed populations will decrease.

In areas where broadleaf weeds are particularly a problem, mow frequently to prevent seed-head production; and after properly identifying the problem weed species, initiate controls. For assistance with identification, consult with your local University of Illinois Extension office or the booklet, “Identifying Weeds in Midwestern Turf and Landscapes” available at: 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. Persistence may be needed but will be rewarded.

Broadleaf plantain in turf. Michelle Wiesbrook, University of Illinois.

Proper cultural practices can greatly reduce weed populations. However, if weed problems persist, herbicides can be used. Postemergence herbicides can provide effective control now that many broadleaf weeds are actively growing again. 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 specific 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.
    1. 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.
    2. Apply these herbicides when air temperatures are between 55 degrees and 85 degrees F.
    3. Adequate soil moisture is important to maintain growth and translocation of herbicides throughout the entire weed.
    4. Do not apply when precipitation is expected within 24 hours.
  2. Don’t mow for a few days before or after application, thereby allowing maximum leaf surface for interception and absorption of the herbicides.
  3. When possible, to reduce unnecessary pesticide use, make spot applications rather than treating large areas.
  4. Apply these herbicides to new turfgrass seedlings only after they have been mowed three or four times unless label directions read otherwise. Wait at least 30 days after application before seeding into areas treated with postemergence broadleaf herbicides.
  5. Many broadleaf weeds such as dandelion and ground ivy are busy preparing for winter by moving excess carbohydrates to the roots. This can aid translocation of a postemergent herbicide. 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 guide, Turfgrass Weed Control for Professionals available from Purdue Extension.  University of Illinois contributes to this publication with expertise and research information. If you still have a copy, the 2014 Commercial Landscape and Turfgrass Pest Management Handbook still contains relevant information. 

Information about common postemergence herbicides follows. Trade names are given as examples only and should not be considered endorsements of any kind. This list is not all inclusive. Often combination products are offered to better control a variety of species.  

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, purslane, 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 but does not control buckhorn or broadleaf plantains well. Dicamba is relatively mobile in the soil. Carefully read and follow label directions as tree roots may pick up dicamba and sensitive species may be injured.

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

fluroxypyr (Tailspin, Vista XRT): Similar in activity to triclopyr.  Can be effective on ground ivy, dandelion, and white clover.

clopyralid (Lontrel): For use on non-residential turf, clopyralid is very active against white clover and thistle.

quinclorac (Drive XLR8): An unusual product, as quinclorac is active against white clover, veronica, dandelion, and crabgrass.

chlorsulfuron (Telar XP):  Labeled for use on unimproved industrial turf, this formulation is not to be used on lawns.  It controls a broad spectrum of weeds.

carfentrazone-ethyl (Quicksilver T&O, 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.

pyraflufen (Octane): Controls chickweed, dandelion, and white clover.  It can be used in newly seeded areas that are not under stress.

topramezone (Pylex): This product has a bleaching effect on susceptible species such as carpetweed, chickweed, and clover. 

penoxsulam (LockUp, Sapphire): This low use product can be used to control many broadleaf weeds including white clover. 

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

2,4-D + MCPP + dicamba (Triad Select, Trimec, Triplet, others)

2,4-D + MCPP + 2,4-DP (Triamine)

MCPA + MCPP + dicamba (Trimec Encore, Tri-Power)

Violets in turf. Michelle Wiesbrook, University of Illinois.

Several preemergence herbicides can be applied to control broadleaf weeds in turf. As mentioned previously, chickweed and henbit will be germinating soon. 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. A few commonly used examples include:

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. Prostrate knotweed germinates very early in the spring and late fall (November even December) applications can be effective.

pendimethalin (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 before weed emergence.

Michelle Wiesbrook, adapted from a previous article by the same author and Tom Voigt

Michelle Wiesbrook

Return to table of contents