Group Title: Circular
Title: Selective weed control
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 Material Information
Title: Selective weed control
Series Title: Circular
Physical Description: 13 p. : ill. ; 28 cm.
Language: English
Creator: McCarty, L. B ( Lambert Blanchard ), 1958-
Florida Cooperative Extension Service
Publisher: Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida
Place of Publication: Gainesville
Publication Date: 1993
 Subjects
Subject: Weeds -- Control -- Florida   ( lcsh )
Turfgrasses -- Florida   ( lcsh )
Herbicides -- Florida   ( lcsh )
Turf management -- Florida   ( lcsh )
Golf courses -- Maintenance -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
 Notes
Statement of Responsibility: L.B. McCarty.
General Note: Title from caption.
General Note: "July 1993."
 Record Information
Bibliographic ID: UF00008567
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: ltqf - AAA6831
ltuf - AJT2172
oclc - 29205827
alephbibnum - 001857778

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UNIVERSITY OF

FLORIDA


Florida Cooperative Extension Service


Selective Weed Control'
L. B. McCarty2


Maintaining today's modern, multi-million dollar
turf complexes at the desired level of aesthetics
requires knowledge of specific weeds, their biology
and available control measures. The following
discusses current selective weed control options turf
managers have at their disposal. Weed control should
be a carefully planned and coordinated program
instead of being a hit-or-miss operation.
Understanding how and why weeds are present on a
site is more important than what control options are
available once the weed is present.

Knowledge of the safety, and effectiveness at
certain weed growth stages, tolerance or susceptibility
of treated turf species, time required for control of
species, and economics are important considerations
when trying to choose between herbicides. The most
effective herbicide is only as good as its application.
Many variables influence successful herbicide
application. These include: proper equipment,
environmental factors at the time of application;
proper and constant calibration and adequate
agitation. Most herbicide failures involve using the
wrong chemical at the wrong date, or they are applied
at an improper time or manner. It is not by failure of
the herbicide itself.

PREEMERGENCE HERBICIDES

Preemergence herbicides form the basis for a
chemical weed control program in turfgrasses and are
used primarily to control annual grasses and certain
annual broadleaf weeds. Preemergence weed control
was first suggested in 1927 and again in 1930. Some


of the first chemicals evaluated for preemergence
weed control included calcium cyanide, arsenate and
naphthylacetic acid. In 1959, the first true and
consistent preemergence herbicide was available for
turf producers. DCPA (dimethyl tetrachlorotere-
phthalate) provided more consistent control with less
damage to the turf than was previously available.
With the subsequent release of dinitroaniline
chemistry the widespread acceptance of preemergence
weed control in turfgrass was established.

" When considering any herbicide, one of the first
questions is the tolerance of the desirable turfgrass
species to the chemical in question. Table 1 lists the
most widely used turfgrass species on Florida golf
courses and their tolerance to currently available
preemergence herbicides. These herbicides such as
bensulide, and members of the dinitroaniline
herbicides family (e.g., benefin, oryzalin,
pendimethalin, prodiamine, trifluralin), should be
used only on well-established turfgrasses.

Effectiveness of Preemergence Herbicides

The effectiveness of preemergence herbicides
varies because of many factors. Included are
application timing in relation to weed seed
germination, soil types, environmental conditions
(e.g., rainfall and temperature), target weed species
and biotype, and cultural factors (e.g., aerification)
that follow application. Preemergence herbicides
generally are most effective for annual grass control
although some annual small seeded broadleaf weeds
also are suppressed. Table 2 lists the expected


1. This document is Circular 1115, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida.
Publication date: June 1993.
2. L. B. McCarty, Associate Professor, Environmental Horticulture Department; Cooperative Extension Service, Institute of Food and Agricultural
Sciences, University of Florida, Gainesville FL 32611.
The Institute of Food and Agricultural Sciences is an equal opportunity/affirmative action employer authorized to provide research,
educational information and other services only to individuals and institutions that function without regard to race, color, sex, age, handicap,
or national origin. For information on obtaining other extension publications, contact your county Cooperative Extension Service office.
Florida Cooperative Extension Service / Institute of Food and Agricultural Sciences / University of Florida / John T. Woeste, Dean


Circular 1115
July 1993






Selective Weed Control


control of common annual grass and several broadleaf
weeds for various preemergence herbicides.

An important consideration in using
preemergence herbicides is application timing. Most
preemergence herbicides act as mitotic inhibitors,
meaning they prevent cell division. Since the
germinating shoot and root tips are the two major
sites of cell division, preemergence herbicides must
contact these in the soil. Application should
therefore be timed just prior to weed seed
germination since most preemergence herbicides are
ineffective on emerged (visible) weeds. If applied too
soon, natural herbicide degradation processes may
reduce the herbicide concentration in the soil to a
level resulting in ineffective or reduced control. If
applied too late (e.g., weed seedlings are visible) the
weeds have grown above the thin layer of
preemergence herbicide located at the soil surface
resulting in the effectiveness of the materials being
drastically reduced (Figure 1).

Crabgrass germinates from February through May
when soil temperatures at a 4-inch depth reach 53 to
580F. Alternating dry and wet conditions at the soil
surface, as well as light, encourage crabgrass
germination. Goosegrass germinates at soil
temperatures of 60 to 650F. Goosegrass also requires
light for seed germination and is very competitive in
compacted soils. Normally, because of higher
temperature requirements for germination, goosegrass
germinates two to four weeks later in the spring than
crabgrass. If herbicides are applied at the time for
crabgrass control, the material will begin to
breakdown in the soil and goosegrass control will be
reduced. Therefore, when developing a goosegrass
weed control program, delay preemergence spring
herbicide application three to four weeks after the
application date targeted for crabgrass control.

Sequential or Repeat Applications

Repeat applications of preemergence herbicides
are generally necessary for full season control. Most
herbicides begin to degrade soon after application
when exposed to the environment. Usually, the level
of degradation that occurs from 6 to 16 weeks after
application reduces the herbicide concentration to the
point that poor control of later germinating weed
seeds occurs. Repeat applications are necessary at
this time for prolonged preemergence weed control.
Note: On those areas to be established with turf,,
most preemergence herbicides should not be used two


Figure 1. Preemergence herbicides form a barrier at or just
below the soil surface and are relatively ineffective on
emerged weeds.

to four months before planting. Otherwise
rootdamage and germination reduction of turfseed
may result. Table 2 lists expected control of selected
weeds with preemergence herbicides.

Core Aerification and
Preemergence Herbicides

Core aeration has not traditionally been
recommended or practiced following a preemergence
herbicide application. Core aeration was believed to
disrupt the herbicide barrier in the soil, thus allowing
weed germination. Research, however, indicates that
core aerification immediately prior to or one, two,
three, or four months after preemergence herbicide
applications does not stimulate large crabgrass
emergence. In the same study, aeration at one or two
months after application increased large crabgrass
cover five percent for oxadiazon at the low label rate
but not at the high rate. In a related study, core
aeration at one, two, or three months after an
application of oxadiazon did not decrease goosegrass
control on a 'Tifgreen' bermudagrass putting green.
Core aeration or vertical mowing immediately or one
month after an application of benefin, bensulide, or
DCPA also did not affect large crabgrass control in
either 'Tifgreen' or common bermudagrass. However,
in creeping bentgrass, significantly greater amounts of
crabgrass occurred in plots that were aerified with the
cores returned than in plots not aerified, or aerified
with the cores removed. ( o



SCIErCE
L IB r,,'..;


Page 2







Selective Weed Control


Annual Bluegrass Control
in Overseeded Bermudagrass

Annual bluegrass is the most troublesome winter
annual weed on golf courses. Its low growth habit
and ability to thrive in moist conditions and
compacted areas make it difficult to control with
management practices alone. Annual bluegrass has a
lighter green color than most grass species used to
overseed golf greens, and its produces numerous
seedheads which disrupt the playing surface. Also,
due to low heat tolerance, annual bluegrass quickly
dies in warm weather, leaving areas bare until the
bermudagrass has time to fill-in. Chemical control of
annual bluegrass is difficult to achieve due to: (1)
inability of the majority of preemergence herbicides
to selectively prevent annual bluegrass germination
while allowing the desirable overseeded grass to
become established, and (2) most postemergence
herbicides effective on annual bluegrass also damage
the desirable overseeded grass species.

Preemergence annual bluegrass control was first
noted in the 1930s when lead arsenate, an insecticide,
was discovered as an effective bluegrass control in
turf. Since then numerous preemergence herbicides
controlling annual bluegrass have been reported.

Preemergence annual bluegrass control is
currently achieved with several herbicides. Each has
its own precautions before use, and if these are not
followed, unsatisfactory results may occur. Pronamide
(Kerb) provides preemergence control of annual
bluegrass in overseeded bermudagrass. Pronamide
must be applied in advance of annual bluegrass
germination and planting of overseeding grass.
Ninety-days is the minimum recommended period
between application and overseeding. It is also
recommended that application not be made where
drainage flows onto areas planted with cool-season
grasses, or onto bermudagrass golf greens.
Superintendents who have to apply pronamide closer
than ninety days prior to overseeding can offset the
problems of ryegrass germination by applying a thin
layer of charcoal. The charcoal will bind the
pronamide and prevent it from' damaging the
overseeded ryegrass. However, the mess and dark
color associated with charcoal applications and the
risk of it not working must be considered before use.
An agricultural grade of activated charcoal should be
applied at two to four pounds per 1000 sq ft and at
least fourteen days should be allowed between
herbicide and charcoal applications. Reseeding


should be no sooner than seven days following
charcoal application.

Ethofumesate (Prograss) also provides
preemergence and early postemergence annual
bluegrass control in bermudagrass. However, to
prevent undesirable turfgrass injury, the application
rate, time, and frequency are important. If applied in
fall before bermudagrass dormancy, an immediate
cessation of bermudagrass growth occurs. A delay in
spring transition from ryegrass to bermudagrass also
occurs with early fall application. Spring green-up of
bermudagrass is also retarded with February
applications. Therefore, ethofumesate use is not
recommended in Florida due to the lack of
completely dormant bermudagrass in most areas.

Fenarimol (Rubigan), a systemic fungicide used to
control several turfgrass diseases, gradually reduces
annual bluegrass populations without adverse effects
to overseeded grasses or to bermudagrass. Application
should occur before overseeding and germination of
annual bluegrass. A treatment scheme has been
suggested consisting of one, two or three sequential
treatments, with the single or final application of the
sequential treatment being two weeks prior to
overseeding. Unlike pronamide, fenarimol does not
appear to affect either overseeded perennial ryegrass
or bermudagrass, but. the necessity of a properly
timed repeat application can be a drawback for
certain managers who have limited budgets and labor.
Inconsistent annual bluegrass control following
fenarimol treatments has been noted.

Bensulide (Betasan, Pre-San) also provides
preemergence annual bluegrass control and an
acceptable stand of ryegrasses is obtainable when
seeding is delayed four months after herbicide
application. This could, however, be influenced by
environment and management practices. The ryegrass
tolerance range is narrow. Current label directions
indicate that 100 lbs per acre of the 12.5G
formulation should be applied (12.5 lbs ai/A). This
four month waiting period allows enough bensulide to
be in the soil to give good control of the germinating
annual bluegrass but also be low enough to not
interfere with germination of the overseeded grass.
If the treated area needs to be seeded sooner than
four months after application, powdered, activated
charcoal can be used to deactivate the bensulide. The
activated charcoal should be applied at a rate of seven
pounds in 14 gallons of water per 1000 sq ft (300 lbs
in 600 gallons of water per acre). The turf should be
irrigated immediately after application to wash the


Page 3







Selective Weed Control


charcoal into the soil. Reseeding should occur no
sooner then seven days after applying the charcoal.

Benefin (Balan) also may be used in overseeded
ryegrass for preemergence annual bluegrass control.
A minimum waiting period of 45 days must be
observed between benefin application and ryegrass
overseeding. This use of benefin is suggested only on
larger areas such as golf course fairways and athletic
fields and not on golf greens.

Due to costs and potential turf injury, it is
recommended that preemergence annual bluegrass
control on golf greens in Florida be attempted only
with products containing fenarimol. Larger, less
intensively maintained areas such as fairways and
athletic fields, should have products containing
pronamide, bensulide or benefin to control the annual
bluegrass in overseeded ryegrass. All pre-cautionary
statement on each product's label should be consulted
before use.

POSTEMERGENCE HERBICIDES

Postemergence herbicides are generally effective
only on those weeds which have germinated and are
visible. Most postemergence herbicides are relatively
ineffective as preemergence herbicides. Timing of
application should be when weeds are young (two to
four leaf stage) and actively growing. At this stage,
herbicide uptake and translocation is favored, and
turfgrasses are better able to fill in voids left by the
dying weeds. Turfgrass species tolerance to
postemergence herbicides are listed in Table 3.

Broadleaf Weed Control

Broadleaf weeds in turf have traditionally been
controlled with members of the phenoxy herbicide
family (e.g., 2,4-D, dichlorprop, MCPA and
mecoprop) and benzoic acid herbicide family (e.g.,
dicamba). All are selective, systemic foliar-applied
herbicides. Few broadleaf weeds, especially
perennials, are controlled with just one of these
materials. Usually, two or three-way combinations of
these herbicides and possible repeat'applications are
necessary for satisfactory weed control. Sequential
applications should be spaced ten to fourteen days
apart.

Until recently, these various herbicide
combinations were the main chemicals for broadleaf
weed control. Chlorflurenol, chlorsulfuron,
metsulfuron, clopyralid, and triclopyr have been


introduced as alternatives to phenoxy herbicides for
broadleaf weed control. Chlorflurenol was previously
used mainly as a plant growth regulator to retard
growth of treated ornamentals and turf. It was noted
to have some broadleaf activity but usually needs to
be mixed with one of the traditional broadleaf
herbicides to increase its activity on a wider range of
weeds.

Triclopyr belongs to the Picolinic Acid herbicide
family. Compounds in this family have been noted
for their high degree of activity. These herbicides are
up to ten times more potent than 2,4-D on some
broadleaf weed species. They are rapidly absorbed by
the roots and foliage of broadleaf plants, and are
readily translocated throughout the plants via both
xylem and phloem tissues. Problems with this
herbicide family include its soil mobility and the
extreme sensitivity to it by many desirable
ornamentals. Clopyralid also is one of the newer
members of this herbicide family. It is currently being
evaluated as a potential broadleaf herbicide on cool-
season turfgrass species.

Metsulfuron, a member of the sulfonylurea
herbicide family, has some success in controlling grass
and broadleaf weeds. Its use rate is extremely low
(0.25 to 1.0 oz product/acre) and is noted for its
activity on controlling bahiagrass. Its full spectrum of
control on broadleaf weeds is not known, but shows
promise as a alternative to the phenoxy herbicides.

Chlorsulfuron, one of the first members of the
sulfonylurea herbicide family to reach the
marketplace, is labelled for selective broadleaf and
tall fescue control in certain cool-season turfgrasses.
Bermudagrass is a warm-season grass tolerant to this
material. Rates range from 1 to 5 oz product per
acre, depending on the weed species present. Table
4 lists the effectiveness of commonly used
postemergence herbicides for broadleaf weed control.

Grass Weed Control

Traditionally, for tolerant turfgrass species,
postemergence grass weed control has been through
single and repeat applications of the organic
arsenicals (e.g., MSMA, DSMA, CMA). Two to four
applications, spaced seven to ten days apart generally
are required for complete control. The rate and
number of applications necessary for weed control
usually increases as weeds mature. On cool-season
turfgrasses, organic arsenicals can be very phytotoxic,
especially when used during high temperatures


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Selective Weed Control


(>900F). Control also is reduced if rainfall occurs
within 24 hours of treatment. Recently, new
herbicide releases have provided alternatives to the
arsenicals for postemergence grass weed control.
Decreased phytotoxicity as well as reduced number of
applications are often associated with these
herbicides. The following discusses herbicides
available for various turfgrass species.

Warm-Season Turfgrasses

Bermudagrass and zoyslagrass. Postemergence
control of crabgrass species and goosegrass have been
with organic arsenicals (e.g., MSMA/DSMA). As
previously mentioned, repeat applications with a short
time interval between applications are required,
especially for goosegrass control. Increasing
phytotoxicity usually results in bermudagrass and
zoysiagrass with repeat applications.

In order to increase herbicidal activity on
goosegrass, various combinations with other
herbicides have been tested with the organic
arsenicals. High rates of metribuzin (Sencor), an
asymmetrical triazine, gives excellent control of
goosegrass, but bermudagrass has marginal tolerance.
Lower rates of metribuzin combined with arsenical
herbicides provides good to excellent goosegrass
control. However, this combination is safely used
only on well established bermudagrass that is actively
growing and also is maintained at mowing heights
greater than 1/2 inch. The use of metribuzin with
MSMA or DSMA increases activity on goosegrass but
a certain degree of phytotoxicity and a number of
escaped weeds still exist. Metribuzin also has been
shown to inhibit photosynthesis of bermudagrass for
a certain period of time.

Diclofop-methyl (Hoelon or Illoxan), a member
of the aryl-oxy-phenoxy herbicide family, has shown
excellent goosegrass control compared to the organic
arsenical and metribuzin combinations. Little damage
to bermudagrass has resulted and repeat applications
are not usually necessary. This herbicide is more
active on younger, lower mowed goosegrass. Weed
control is relatively slow, often requiring two to three
weeks to take effect. The weed control spectrum also
appears to be limited, with goosegrass being the most
susceptible grass species. Treated areas should not be
overseeded with perennial ryegrass for at least six
weeks after herbicide application. Diclofop also
should not be mixed with any other postemergence
herbicides, especially 2,4-D, MSMA, or metribuzin as


reduced goosegrass control and increased turfgrass
phytotoxicity may result.

Fenoxaprop-ethyl (Acclaim), another member of
the aryl-oxy-phenoxy herbicide family, has been shown
to control annual grass weeds, crabgrass species in
particular. Zoysiagrass and at much lower rates,
bentgrass, have acceptable tolerance to fenoxaprop.

Bahlagrass. Bahiagrass, like St. Augustinegrass,
is somewhat sensitive to most postemergence
herbicides. This sensitivity limits the choices of
materials available for use on it. Although labeled for
use on bahiagrass, most postemergence broadleaf
(e.g., 2,4-D, dicamba, and/or mecoprop) herbicides
will result in yellowing, especially if applied when
temperatures are hot or the turf is growing under
stressful conditions. Normally, the phytotoxicity is not
lethal, and recovery can be expected within one to
two weeks.

Selective postemergence grass weed control in
golf course grown bahiagrass is not currently
available. Spot treatment with a nonselective
herbicide, such as glyphosate, is the only chemical
method of control.

Cool-Season Turfgrasses

Postemergence grass weed control in cool-season
turfgrasses has previously been limited to various
members of the organic arsenicals. Specific
formulations (e.g., CMA) and rates are necessary for
use on most cool-season turfgrasses or unacceptable
levels of injury may result. Proper timing at a young
weed-growth stage, during mild environmental
conditions, and actively growing turfgrasses are
specific considerations before using any of these
herbicides.

Nutsedge Control


The predominant nutsedge weed species in
turfgrasses are yellow and purple nutsedgee. Other,
more local members of the Cyperus genus include
annual or water sedge, perennial and annual kyllinga,
globe sedge, Texas sedge, flathead sedge and
cylindrical sedge. Path or slender rush, a member of
the rush (Juncus) family, also can occur in some turf
situations.

These weeds generally thrive in soils that remain
wet for extended periods of time due to poor
drainage or excessive irrigation. The first step in


Page 5







Selective Weed Control


nutsedge weed control is, therefore, to correct the
cause of continuously wet soils. Do not over-irrigate
an area and, if necessary, provide surface and
subsurface drainage.

Yellow and purple nutsedges are low-growing
perennials resembling grasses. Nutsedges, in general,
are yellow-green to dark-green, with triangular stems
bearing three-ranked leaves-unlike the two-ranked
leaves of the grass family. The root systems are
fibrous with deep-rooted tubers or nutlets that are
*able to reproduce. Seedhead color is often used to
distinguish between these two major nutsedges. Leaf
tip shape is another distinguishing method. Leaf tips
of purple nutsedge are generally thicker and more
rounded than yellow nutsedge leaf tips which are
narrowing, forming a needle-like end. Yellow and
purple nutsedge have a great capacity to reproduce
and spread due in part to their massive underground
tuber and rhizome systems.

Historically, chemical control of most sedges was
with repeat applications of 2,4-D or the organic
arsenicals (MSMA, DSMA). Although effective, the
treatments are slow to kill the weeds and repeat


applications are generally necessary resulting in
extensive damage in certain turf species.

Selective yellow nutsedge control is now available
with bentazon (Basagran T&O) with minimum turf
damage. Control of most other nutsedges also will
result from bentazon treatments. Bentazon is a
contact material, meaning it will control only those
portions of the weeds treated with it. Complete
coverage of the weeds is, therefore, necessary for
greatest bentazon activity. Even with good herbicide
coverage, regrowth will normally occur from the roots
and tubers and repeat applications will be necessary.

Purple nutsedge can be suppressed with
imazaquin (Image). Selective broadleaf weeds, such
as wild garlic, are also controlled with imazaquin. As
with bentazon, repeat applications-possibly over
several years-will be required to control all the
underground reproductive parts with imazaquin. The
addition of MSMA increases the activity of either
bentazon or imazaquin and broadens the range of
weeds controlled. However, this should be used only
on bermudagrass or zoysiagrass and imazaquin should
be used only on actively growing turfgrass.


Page 6





Selective Weed Control


Table 1. Established turfgrass tolerance to preemergence herbicides1

Preemergence Bentgrass Bermudagrass
Herbicides Bahiagrass Bentgrass golf green Bermudagrass golf green Centipedegrass

atrazine D D D I D T

benefin T I D T D T

benefin + oryzalin T D D T D T

benefin + trifluralin T D D T D T

bensulide T T T T T T

bensulide + oxadiazon D I-T I-T T T D

DCPA T I D T D T
dithiopyr T T T T T T
ethofumesate D D D I D D

fenarimol T D D T D D
isoxaben T T D T D T
metolachlor T D D T D T

napropamide T D D T T T
oryzalin T D D T D T

oxadiazon D D D T D D
pendimethalin T D D T T T

prodiamine D I-T D T D T

pronamide D D D T D D

siduron D I I D D D

simazine D D D I D T


Page 7








Selective Weed Control


Table 1. Established turfgrass tolerance to preemergence herbicides (cont.)

Preemergence Kentucky
Herbicides bluegrass Perennial ryegrass St Augustinegrass Tall fescue Zoysiagrss

atrazine D D T D I-T
benefin T T T T T
benefin + oryzalin D D T T T
benefin + trifluralin T T T T T
bensulide T T T T T
bensulide + oxadiazon T D D T T
DCPA T T T T T
dithiopyr T T T T T
ethofumesate D T D D D
fenarimol D T D D D
isoxaben T T T T T
metolachlor D D T D D
napropamide D D T T D
oryzalin D D T T T
oxadiazon T T T T T
pendimethalin T T T T T
prodiamine T T T T T
pronamide D D D D D
siduron T T D T T
simazine D D T D I-T
1T = Tolerant at labeled rates; I = Intermediate tolerance; D = Damaging or not registered for use on this turfgrass


Page 8





Selective Weed Control


Table 2. Expected control of selective weeds with preemergence herbicides1

Preemergence Annual Common Lawn Com
Herbicides Crabgress Goosegrass Bluegrass Chickweed Henbit Burweed Speedwell

atrazine P-F P E G G E G

benefin G-E F G-E G G F G

benefin + oryzalin E G E G G -- --
benefin + trifluralin E G E G G -- --
bensulide G-E P-F F F F F F

bensulide + oxadiazon E G-E / -- -- -- --
DCPA G-E F G E F P E
dithiopyr E G-E G-E -- -- E
fenarimol P P G P P P P
isoxaben F P F G G -- --
metolachlor F-G F F-G -- -- -- --
napropamide G-E G G E P E E
oryzalin E F-G G-E G G -- --
oxadiazon G E G P P P G
pendimethalln E G-E G-E E G -- E
prodiamine G-E G-E G -- -- -- --

pronamide F P G-E E P P G
siduron F P P P P P P

simazine F P E G G E G
1E = Excellent, >89% control; G = Good, 80 to 89% control; F = Fair, 70 to 79% control, P = Poor, <70% control


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Selective Weed Control


Table 3. Turfgrass tolerance to postemergence herbicides1 __ K nuk
Postemergence Hebicides Bahiagrass Bentgrass Bermudagrass Carpetgrass Centipedegrass Kentucky bluegrass
asulam D D I-T D D D
atrazine I D I T T D
bentazon T T T T T T
bromoxynil T T T -- T T
chlorflurenol T D T -- T T
chlorsulfuron T I T D T
clopyralid D D I-T -- D T
2,4-D T D-1 T I-T D-I T
2,4 + dicamba T D-1 T I-T D-l T
2,4-D + dichlorprop T D-1 T I-T I-T T
2,4-D + mecoprop (MCPP) T I T I-T D-l T
2,4-D + MCPP + dicamba T D-* T I-T D-I T
2,4-D + triclopyr D D-I D-I I-T D T
dicamba T I T T I-T T
DSMA,MSMA D I T D D I-T
fenoxaprop I D D -- D T
imazaquin D D T I-T T D
MCPP T T T I-T D-1 T
metsulfuron D-1 D T II-T I-T
metribuzin D D T -- D D
pronamide D D T --D D
quinclorac D D T -- D T
sethoxydim D D D D-I T D
simazine I D I T T D


Page 10




Selective Weed Control


Table 3. Turfgrass tolerance to postemergence herbicides (cont)

Postemergence Herbicides St Augustinegrass Perennial ryegrass Tall fescue Zoyslagrass

asulam I D D D
atrazine T D D
bentazon T T T T
bromoxynil T T T T
chlorflurenol T T T T
chlorsulfuron D D D D
clopyralid D T T I-T
2,4-D D-I T T T
2,4 + dicamba D-l I T T
2,4-D + dichlorprop D-I I T T
2,4-D + mecoprop (MCPP) D-1 I T T
2,4-D + MCPP + dicamba D-I I T T
2,4-D + triclopyr D I T D
dicamba D-I T T T
DSMA, MSMA D I I-T I
fenoxaprop D T T I
imazaquin T D D T
MCPP D-I T T T
metsulfuron I-T D I-T I
metribuzin D D D D
pronamide D D D D
quinclorac D T T T
sethoxydim D D D I
simazine T D D I
T = Tolerant at labeled rates; I = Intermediate tolerance, use at reduced label rates; D = Damaging, do not use this herbicide
ir it is not registered for use on this turfgrass
Tolerance depends on specific product formulation, timing of its application and its applied rates


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Selective Weed Control


Table 4. Susceptibility of broadleaf weeds to turf herbicides1

Atrazine/ Mecroprop 24-D + 24-D + 2,4- + MCPP 24-D +
Weed ifecycle Simazine 2,4-D (or MCPP) Dicamba MCPP dichlorprop + dicamba triclopyr Metulfuron Quincorac

Betony, Florida P S-I I I I-S I I I-S -
Bittercress, hairy WA S I S S S S -
Bindweed, field P S-I I S S-1 S S -
Black Medie A R I S I S S -
Burclover A I-R S S S-I S R
Buttercups WA, B&P I S-I I I-R S S S -
Buttonweed, Va. P S-1 I I I S-I S-I I-R -
Carpetweed SA S S I S S S S -
Carrot, wild A, B I I S I S- S S -
Catsear P S-I I S S S S- -
Chickweed, common WA S R S-I S S S S S S R
Chickweed, mouse-ear WA, P I I-R S-1 S S S S S-1 R
Chicory P S S S S S S S
Cinquefoil, common P S-I S-I S-I S-1 S-I S-1 --
Clover, crimson SA S S S S S S S
Clover, hop WA S I S S S S S S S
Clover, white P S I S S S S S S-I S S
Daisy, English P R I S I I S -
Daisy, oxeye P, B I I I I I S-I -
Dandelion P I-R S S S S S S I-S S I
Dichondra P S-1 S I S-I S S S -
Dock, broadleaf & curly P I I I-R S I I S-I I I
Garlic, wild P S-1 R S-I S-1 S-1 S-1 S-I R
Geranium, Carolina WA S S-I S S S S S-I -
Hawkweed P S-I R S-I S-1 S-I S-I -
Healall P S R S-I S S S -
Henbit WA S I-R I S I S-1 S S S-I R
Ivy, ground P I-R I S-I I I-S S-1 R
Knawel WA R I S S-I S-1 S -


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Selective Weed Control


Table 4. Susceptibility of broadleaf weeds to turf herbicides (cont)
Atrazine/ Mecroprop 2,4 + 2,4-D + 2,4-D + MCPP 2,4- +
Weed Ufecycle Simazine 2,4-D (or MCPP) Dicamba MCPP dichlorprop + dicamba ticopyr Metsulfuron Quinclorac

Knotweed, prostrate SA S R I S S-1 S-I S R
Lambsquarter, common SA S S S S S S S-1 I
Lespedeza SA S I-R S S S-1 I S -
Mallow P I-R I S- S-1 S-I S-1 -
Mugwort P I I-R S-1 I I I -
Mustard, wild WA S S I S S S-I S I
Onion, wild P I R S-I I I S S-I R
Parsley-piert WA S R S-1 S-1 S-I R S-I S -
Pearlwort WA S-1 S-1 S-1 S-I S-I -
Pennywort, lawn P S S-I S-I S-I S-I S-1 S-1 -
Pepperweed A S S-I S S-1 S S -
Pigweed A,P S S S S S S S-I I
Plantains P I-R S I-R R S S S I-R I I
Purslane, common SA I R S I I S-I I R
Red sorrel P R S S S-I S S R
Shepherd's-purse WA S S-I S S-I S S R
Speedwell, corn WA S I-R I-R I-R I-R I-R I-R -
Spurge, postrate SA S-I I I S I S-I S-I S-I I
Spurge, spotted SA S I-R S-I S-1 S-I S-I S S-1 -
Spurweed (lawn burweed) WA S-1 I S-1 S S-1 I S -
Strawberry, India mock P R I S-I I R S-I -
Thistles B,P S-1 I S S-I S-I S I -
Violet, johnny-jumpup WA I-R I-R S-1 I-R I I-R -
Violet, wild P I-R I -R S-I I-R I I-R I-R -
Woodsorrel, yellow P I R R I I-R I-R I-R S-1 R
Yarrow P I I-R S I-R I S-1 S-I -
Yellow rocket WA S- I S-I S-I S-I S -
1A = annual; B = biennial; P = perennial; SA = summer annual; WA = winter annual; S = susceptible; I = intermediately susceptible, good control sometimes with high rates,
however a repeat treatment 3-4 weeks later each at the standard or reduced rate is usually more effective; R = resistant in most cases. Not all weeds have been tested for
susceptibility to each herbicide listed.


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