The development and maintenance of a dense, healthy stand of
grass is the best way to reduce the incidence of broadleaf weed
problems developing in home lawns. To facilitate the production
of healthy lawns, homeowners should incorporate recommended
turfgrass selections and management practices into their
establishment and maintenance programs. These recommendations
include the use of adapted species and cultivars, adequate
fertilization programs, proper mowing practices, adequate
supplemental irrigation, and necessary insect and disease control
measures. Occasionally however, even the best cared-for lawns
are sometimes invaded by broadleaf weeds. To have a completely
weed-free lawn, the homeowner may have to resort to the careful
and selective use of braodleaf weed control herbicides.
POSTEMERGENT HERBICIDES can be used to control broadleaf weeds
(i.e., non-grassy weeds) that are not prevented with the use of
preemergent herbicides. It is essential that sensible cultural
practices be used to encourage rapid fill-in soon after the turf
has been treated with the weed control chemical, since new weeds
will quickly reinfest the areas left open by the recently-killed
weeds. For this reason, HERBICIDE USE SHOULD BE REGARDED AS ONLY
ONE TOOL IN THE TOTAL WEED CONTROL PROGRAM.
WHICH HERBICIDE TO USE? Before using a postemergent herbicide
for broadleaf weed control, it is important to identify the
weed(s) which you are attempting to control. The reason is that
not all weed species are controlled via the use of one specific
herbicide. The homeowner may need to use a combination of two or
more herbicides to obtain the desired control. If you can not
identify the weed(s) in question, seek help from garden center
personnel, your county Extension agent, or from the Plant Pest
Diagnostic Clinic (The Ohio State University campus; 614/292-
5006).
The most readily available chemicals to homeowners for
selective, postemergent control of broadleaf weeds include: 2,4-
D, 2,4-DP, MCPP, and dicamba. These chemicals are available
alone, and in various combinations with each other. Combination
products are recommended for difficult-to-control weeds or when a
variety of weed species is present in the lawn. All are
available in liquid formulations (sprayable), and often in
granular formulations (generally with a fertilizer) which can be
applied with a drop or broadcast spreader. All of the chemicals
listed above are safe for use on Kentucky bluegrass, perennial
ryegrass, tall fescue, and fine fescue lawns IF THE DIRECTIONS ON
THE LABEL ARE FOLLOWED. MCPP is the safest of the listed
herbicides to use on bentgrass lawns.
WHEN TO APPLY? Applications of herbicides intended for
postemergent broadleaf weed control will only kill those weeds
present at the time that the herbicide is applied. They DO NOT
prevent weed seeds from germinating and developing in the lawn at
a later date. It is also important to remember weeds must be
actively growing when the herbicides are applied so effective
control can be achieved. This means that spring applications
should be made from mid-April through early June, and fall
applications should be made during the months of September and
October. Herbicide applications during July and August are
strongly discouraged because not only will weed control be more
difficult to achieve but also an increased risk of causing
damage/ discoloration to the lawn.
HOW TO APPLY? Liquid and granular formulations of herbicides can
be equally effective if they are used properly. Neither should
be applied if rain is expected within 24 hours of application.
For best results, the turf should NOT be mowed or watered for at
least 24 hours following application of either granular or liquid
products. Granular herbicides will be most effective if applied
to grass that is moist (from morning dew, rainfall, or
irrigation) because the granules will adhere to the wet surfaces
of the weeds.
Care should always be exercised when applying herbicides near
trees, shrubs, flowerbeds, and vegetable gardens. Drift from
spray applications or misdirected application of granular
products can result in damage or death of these plants. It is
important that dicamba NOT be applied within the dripline of
trees or shrubs. Dicamba can be root absorbed by these plants,
possibly resulting in damage.
| Weed Control |
Life Cycle(1) |
Recommended Chemical(2) |
Time of Application |
Degree of Control |
| Bindweed |
P |
2,4-D ester or dicamba(4) |
early summer |
good |
| Black medic |
A |
dicamba(4) |
early spring |
good |
| Chickweed, common |
A |
MCPP or dicamba(4) |
spring or fall |
good |
| Chickweed, mouse-ear |
P |
MCPP or dicamba(4) |
fall or spring |
good |
| Chickory |
P |
2,4-D |
spring |
good |
| Cinquefoil |
P |
2,4-D |
fall or spring |
good |
| Dandelion |
P |
2,4-D or dicamba(4) |
fall or spring |
good |
| Dock, curly |
B |
2,4-D or dicamba(4) |
fall or spring |
good |
| Garlic or onion |
P |
2,4-D ester |
late fall, early spring |
fair |
| Ground ivy |
P |
dicamba(4,6) |
summer, fall or spring |
fair-good |
| Heal-all |
P |
2,4-D |
spring |
good |
| Henbit |
A |
dicamba(4) |
spring |
good |
| Knotweed |
A |
dicamba(4,6) |
spring to mid-summer |
good |
| Mallow roundleaf |
A |
dicamba(4) |
spring |
fair |
| Pigweed |
A |
2,4-D or MCPP |
summer |
good |
| Plantain, buckhorn |
P |
2,4-D or MCPP |
fall or spring |
fair |
| Plantain, common |
P |
2,4-D or MCPP |
fall or spring |
good |
| Poison ivy |
P |
Amitrol-T or Roundup(5) |
spring or summer |
good |
| Purslane |
A |
dicamba(4) |
spring or
fall |
good |
| Red sorrel |
P |
dicamba(4) |
spring, summer or fall |
good |
| Speedwell, creeping |
P |
2,4-D, MCPP or Dicamba |
fall or spring |
good |
| Speedwell, annual |
A |
dacthal |
spring or fall |
fair |
| Spurge, spotted |
A |
dicamba(4,6) or MCPP |
summer |
fair-good |
| Sow thistle |
A |
2,4-D or dicamba(4) |
fall |
good |
| Thistle(3) |
P |
dicamba(4) |
spring |
fair-good |
| Wild violet |
P |
dicamba(4,6) or triclopyr |
spring or fall |
fair-good |
| White clover |
P |
MCPP or dicamba(4) |
spring, summer or fall |
good |
| Wild
carrot |
B |
2,4-D or dicamba(4) |
fall or spring |
good |
| Wood sorrel (Oxalis) |
A |
2,4-D ester, MCPP or dicamba(4,6)
|
early summer |
fair-good |
| Yarrow |
P |
dicamba(4) |
spring |
fair |
|
(1) A = Annual, B = Biennial, P = Perennial.
(2) Do not use 2,4-D on golf course greens and use with caution
on other bentgrass turf.
(3) Three or more applications may be necessary to eradicate
thistle.
(4) Dicamba may accumulate in the soil with frequent or
extensive use which may result in damage to trees, shrubs, or
other ornamentals.
(5) Nonselective herbicides. Spot treat only.
(6) 2,4-D plus dichlorprop (Weedone formulations) 2,4-D plus
triclopyr (Turflon formulations) and triclopyr plus
clopyralid (Confront) are effective combinations for many
broadleaf weeds, including hard-to-control species such as
ground ivy, wood sorrel (oxalis), spotted spurge and wild
violets. |
Prepared by:
William E. Pound
Extension Agronomist
John R. Street
Extension Agronomist
-----------------
All educational programs conducted by Ohio State University Extension
are available to clientele on a nondiscriminatory basis without regard
to race, color, creed, religion, sexual orientation, national origin,
gender, age, disability or Vietnam-era veteran status.
Keith L. Smith, Associate Vice President for Ag. Adm. and
Director, OSU Extension.
TDD No. 800-589-8292 (Ohio only) or 614-292-1868
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