Identification and Control of
Difficult Pasture Weeds
Dr. Steve Livingston
Professor and Extension Agronomist
Texas Cooperative Extension
Corpus Christi, Texas
Topics to Cover
• Identification
• Improved pastures & introduced
grasses
• Native grasses
• Invader grasses
• Undesirable grasses
• Chemical weed control
• Keeping the stand
Everyone wants good hay, with no trash in the hay ring
Its hard to see inside the bale; weed carcasses,
brush sprouts, sticks, undesirable seed…
The time to control broadleaf weeds is when they are small
Less product needed, better control,
greater grass production
Perennial escapes often go on to produce seed.
Bermudagrass Weed Control
(establishing the stand)
• 1 qt 2,4-D amine (not labeled)
• 1-2 qt of Weedmaster for newly
established bermudagrass. Up to a
week after planting
• Roots growing in 7-10 days
• With 6 inches of stolon-growth, apply
up to 1.5 pints of Grazon P+D
Weed
Control
(Keeping the stand)
• 2-7 pounds of grass will be produced
for every pound of weeds/acre
eliminated.
• Fertilization without weed control
increases weed growth with little added
grass production.
• Many weed species germinate earlier
than spring grasses will green-up.
Invader Grasses
• Will increase during drought, dormant
periods and when grazing management is
poor.
• Often not controlled by conventional
chemical products.
• May not be totally useless, but damage the
market you are trying to build (appearance,
contamination, feeding value).
• Less productive, lower quality, etc.
• May sometimes be removed with wipers or
rollers where there is a “height differential”.
What grass has invaded this hayfield?
Johnsongrass Control
(Sorghum halepence)
A single plant can produce 80,000 seed which shatter
easily; and 275 feet of rhizomes
• Carpet Roller, Wicker, Wiper…
1 part RU or TD + 2 parts water
wipe or wick in two directions
• Spot treatment with RU or TD
• Plateau (residual supplies only)
• Maverick (roadside label)
Johnsongrass in Coastal Bermudagrass
A = Carpet Roller
B = Blade Cleaner
What is this invader grass?
Burning and mowing
don’t control smutgrass
but contribute to its
spread.
Small Smutgrass, Sporobolus indicus
• A native bunch grass of tropical Asia which has become a serious weed
problem in improved perennial pastures.
• Often infected with a black fungus, which gives a compact appearance.
• As many as 1200 seed/seedhead and 45,000 seed/plant.
• Seed spread by adhering to LS or by wind.
• Only 9% germination 1st year; most seed germinates within 2 years.
General Smutgrass Control Recommendations
1. Do not apply Velpar® within 100 feet of oak trees because it will
cause death.
2. Read the Velpar® label for complete instructions on re-application/
interval, safety and cattle withdrawal interval.
3. If the initial smutgrass density covers greater than 80% of the area,
(if 8 out of 10 regular steps touch the base of smutgrass plants),
complete renovation should be considered, since little other bahia or
bermudagrass would be available for recovery.
4. However, studies indicate that bahiagrass will do an excellent job of
recovery at 70 to 80% smutgrass infestation.
5. Perennial grasses will turn slightly yellow within 15-20 days of application,
and will turn dark green (darker than the untreated grass) in about 40 days
following the Velpar® application.
Chemical Control of Smutgrass
Broadcast spraying with 1.5 qt/A (1.0 lb a.i./A) Velpar® plus 0.1% NIS v/v to
actively growing plants between July and early September results in 90%
control of small smutgrass in perennial pastures. Greater than 90% control of
giant can be made with the 2.0 qt/A rate.
Mowing giant smutgrass to a 3-inch stubble and allowing the plants to re-grow
back to a 12-inch height before spraying with 2.0 qt/A Velpar® did not provide
better smutgrass control than a non-mowed treatment. Mowing 3X at 30-day
intervals did not improve giant smutgrass control
The timing of the Velpar® application during the summer months is extremely
important because rainflal is a necessary component of good smutgrass control.
It is equally important to read the Velpar® label for complete instructions on
application, safety, and casttle withdrawal (60 days).
What is this tall prolific grass-like pasture weed?
Cattle may graze flat sedge some when it is young and tender
Chemical Flat Sedge Control
• There are several types of sedges that are appearing in
pastures due to wet weather, flooding and poor drainage.
Sedges favor wet conditions and will grow where other
grasses cannot.. Four states have received Section 18's
for Maverick or Outrider. Maverick is a wheat pasture
herbicide and Outrider is a roadside herbicide. Neither is
labeled for bermudagrass pastures. In experimental
plots, a 1 oz/A treatment, post emergence, will cause
sedge to react in about 7 days. In 14-21 days, it is a
“crispy critter”. The best time to treat is when it is 6-8
inches tall or less. I cannot recommend these products
until a Section 18 is approved for Texas.
Practical Control Includes Mowing
• Green Flatsedge, Cyperus virens, a sedge
weed that is overtaking rangeland in Victoria
County.
• On rangeland, applications of Grazon P+D
and 2,4-D have proven effective at reducing
populations when shredded prior to
application, and where a spring and fall
application was made (see Victoria County
1998 sedge test).
Spraying Unmowed Flat Sedge
Field After Mowing
Table 1. Green Flatsedge control and economics using various
herbicides . Blake Shaw, Cooperator, Victoria County, TX 1998.
Evaluated 5/19/98
Shredded
Treatment
Rate/
AC
% BurnDown
% Kill
Un-Shred
Evaluated 11/20/98
Shredded
Herbicide
Cost (3)
Un-Shred
% Burn- % Kill Height % Kill Height
Down
(1)
$/Ac
Grazon P+D
1 qt
30
0
30
70
15
50
24
$
6.30
Grazon P+D
1 ½ qt
35
0
20
80
12
60
24
$
9.45
Grazon P+D
2 qt
50
2
30
95
12
80
18
$
12.60
Weedmaster
1 qt
40
2
30
78
12
65
24
$
6.45
Weedmaster
1 ½ qt
35
2
30
78
12
75
24
$
9.68
Weedmaster
2 qt
80
5
35
94
12
85
18
$
12.90
2,4-D
1 qt
20
0
35
60
18
65
18
$
3.14
2,4-D
1 ½ qt
25
1
30
75
12
80
18
$
4.69
2,4-D
2 qt
35
0
40
85
12
87
12
$
6.26
Remedy
½ qt
15
0
35
30
24
12
24
$
10.81
Remedy
1 qt
20
0
30
55
18
82
18
$
21.63
1 ½ qt
40
0
40
35
24
50
24
$
32.44
Remedy (2)
Check
—
0
0
0
0
28
0
28 $
(1) Height in inches of surviving Green Flatsedge.
(2) Encountered sprayer problems during application; percent
kill adversely affected.
(3) Herbicide costs:
Grazon P+D - $126.00 per 5 Gallons
Weedmaster - $64.50 per 2 ½ Gallons
2,4-D - $31.25 per 2 ½ Gallons
Remedy - $86.50 per Gallon
0.00
What is this coastal invader grass?
Bahiagrass Identification by head shape
Bahiagrass Control
Paspalum notatum
• Apply 3/10 oz/A Ally (Dupont Cimarron),
Feb-May, after green-up, but before
bahiagrass seed formation. Best
results when adequate moisture is
available.
• Apply 6 oz/A Plateau (residual supplies)
Apply after the bermudagrass has
greened-up. Most BGs will be yellowed
and will lose one cutting.
What is this invader grass?
Control of Dallisgrass
(Paspalum dilitatum)
• Plateau (residual supplies) applied at 8-12
oz/A (suppression).
• MSMA (can be toxic to some warm season
grasses)
• Glyphosate (tough on non-target plants)
• Revolver, Monument (turf only, not labeled
pasture)
•
Hayproducer’s Nightmare?
Low, thick mat of grass; not erect like coastal.
Summer Annual
Favors sandy or
well-drained soils
Flattened leaves
Purplish tinge at
bottom
Controlling Field Sandspur (sandburr)
• Plateau . Use 2 oz/A @ full greenup
• 1 pt/A glyphosate (RU) w/i 7 days of
first harvest w/no injury to
bermudagrass. (burrs have basal
leaves, but bermudagrass leaves are
basically gone)
• New spriggings; use Direx
Taking Out the Broadleaves!
• Conduct a pasture weed survey.
• Identify and spray weeds when they are
small.
• Consider 3 application periods, depending
on weed problems found: February, June
and September.
• No application will hold broadleaf weeds
indefinitely. Every rain brings new weed
populations, but many will not survive if the
pasture is being managed well.
Old Man’s Beard
Bull Thistle
Bull Nettle
Carolina Geranium
Curly Dock
Common Mallow
Woodsorrel, Chervil
Plaintain
Wild Mustard
Ground Cherry
Mexican Primrose
Texas Bindweed
Antelopehorn Milkweed
Antelope Horn Milkweed
Asclepias viridis
Controlling Milkweed
(hard after 2-4 inches tall)
1. P+D
2 qt/A, partial
( if < 4”)
2. Fuego
12.5 oz/A (slow)
3. Cimarron Max
Rate 1
4. Tordon 22
1 pt + 1 lb/A 2,4-D
5. Weedmaster
2 pt/A pre-flower
(this is a perennial)
What is this?
Texas Bullnettle Control
99
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90
80
70
60
50
40
30
20
10
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99
99
99
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94
90
LSD=10
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Broadcast Treatment – 2 pt/A
97
100
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80
70
60
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Worst of the Worst Weeds
(7 DAT Ratings, 3/27/05)
Herbicide Treatments - Livingston, 2005
Weed ID
WM D-A D-E P+D CM RDM PG SMTL SMTH
1. Western Ragweed
2
2
2
4 4
4
2. Bull Nettle
2
1
2
1 5
1
5
2
2
3. Old Man’s Beard
3
2
2
2 3
1
4
2
2
4. Silverleaf Nightshade 1
1
5
1
5. Crownbeard
1
1
1 1
1
2
2
1
6. Frostweed
3 3
7. Bladderwort
2
1
3
2 2
1
2
8. Queen’s Delight
2
1
1
2
9. Texas Woolly Croton 3
4
4
4
5
3
4
____________________________________________________________
Total Score 1-5 ratings
WM = Weedmaster, D-A = 2,4-D Amine, D-E = 2,4-D Ester, P+D is picloram and
2,4-D, CM = CimarronMax, RDM = Redeem, PG = PastureGard, SMTL = low rate
of Surmount, SMTH = high rate of Surmount
PastureGard is Death on
Bull Nettle, 14 DAT, 4/1/05
Welder Wildlife Refuge
What is this broadleaf perennial weed?
Silverleaf Nightshade
Solanum elaeagnifolium
Smoother leaf margins
Smooth Stems and midribs
Horsenettle,
Tomato Plant
Puckered leaf margins
Spiney stems and midribs
Similar flowers and berries
Horsenettle
Solanum carolinense
Controlling Solanum Species
Control Perennials @ Full Flowering
(Carbohydrates are moving downward
to the roots, making it easier to kill)
1. P + D
3. Weedmaster
1. Cimarron Max
2 qt/A
1 qt/A SLNS
2-3 qt/A HN
Yes LUR
Crotons
Doveweed
Goatweed
Croton Monanthogynus
Wooly Croton
Croton Capitatus
Texas Croton
Croton Texensis
Another type of croton
Tropic Croton
Croton glandulosus
Wooly Croton
How to Control Crotons
P+D>CM>2,4-D
1. 2,4-D Amine
(very deadly, no residual)
1-4”, ½ pt; 4-12”, 1 pt; 12-30, 1.5 pt
2. P + D
Better (has residual, 2-3 mo)
3. Fuego
weak last place
4. Ally
(very small only)
5. Cimarron Max
OK (< residual;
1 mo)
What weed is this?
Prickly leaves that are wooly white beneath
Thistle rosette
Texas Thistle
Circium texanum
Has no ray flowers
Prolific Seed Production
Controlling Texas Thistle
•
•
•
•
2,4-D Amine
P+D
Cimarron Max
WM
11
1 qt/A at rosette stage
1 qt/A E spring; 2X later
Rates 1-3 (1-4 pt/A)
2 pt/A in rosette
What is this weed found in neglected pastures
or unsprayed rangeland?
Western Ragweed
Ambrosia cumanensis
Controlling Western Ragweed
(perennial broadleaf)
1. Weedmaster ½ pt @ 1-3”
2 pt/A active growth
2. P + D
ES 1-2 pt/A < 3” tall
3-4 pt/A 3”-E Flower
HV = 1 gal/100 gal
NGT 1 gal P+D/A
This beautiful golden weed often accompanies willow baccarus in unfertilized
abandon or neglected pastures and hayfields.
Almost nothing will eat it. Resinous sap and strong smell.
Broomweed
Common Broomweed
Gutierrezia dracunculiodes
A native annual
Controlling Common Broomweed
1. Cimarron Max Rate 1
2. WeedMaster
½ pt/A @ 1-3 inches
(4 pts post branching)
1. 2,4-D Amine
(if young)
2. P + D
same rates as WM
3. Fuego
12 oz/A?
Docks
Curley Dock
Rumex crispis
Broadleaf Dock
Rumex obtusifolius
Controlling Rumex Species
(curley dock)
• Most BL pasture herbicides will kill
docks in the rosette stage. Can use
½ rate; however, when it begins to
bolt, must use high rate to control.
• Most people don’t see it when its small
P+D
ES 2 pt/A; Mid/Late Season,
3-4 pt/A (bolting to bud)
Fuego @ 8-12 A/container
Cimarron Max @ Rate 1
False Ragweed
Smooth Groundcherry
Physalis subglabrata
Beebaums (various colors)
Lemon Beebaum (Horsemint)
Monarda citriodora
Controlling Monarda
(Horsemint)
1. 2,4-D Amine 2 pt/A Pre Bloom
3 pt/A Post Bloom
2. P + D
1 qt (easy to kill)
(if young almost anything will kill it)
Delicate leaves, sharp nettle, small white to
Purple flowers. Tall plant moves from fencerow
To hayfield.
Fireweed
Resistant to low rates of atrazine or Bladex
Kill with dicamba or 2,4-D
Fireweed, Heartleaf Nettle,
Weak Nettle, Ortigula,
Dog Nettle, Burning Nettle
Urtica urins
Quiz Time; Gotcha!
If you’ve come to drink at the fountain
of knowledge, this is good for 1 CEU IPM
Good students have their markers ready!
1
What grass has invaded this hayfield?
2
What is this invader grass?
3
What is this tall prolific grass-like pasture weed?
What is this coastal invader grass?
4
What is this invader grass?
5
6
Hayproducer’s Nightmare?
7
8
What is this broadleaf perennial weed?
9
10
11
12
Prickly leaves that are wooly white beneath
13
14
15
16
17
18
18
19
Key to Preview Test
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
Johnsongrass
Smutgrass
Flat Sedge
Bahia grass
Dallis grass
Sandburr
Antelope Horn Milkweed
Bull Nettle
Horsenettle
Silverleaf Nightshade
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
Doveweed (Croton)
Texas thistle
Western Ragweed
Broomweed
Curley Dock
Wideleaf Dock
False Ragweed
Ground cherry
Horse Mint
Fireweed
The End