What to Do About Weeds
Developed by:
Susan Donaldson
University of Nevada Cooperative Extension
UNCE, Reno, Nev.
Topics to be covered
 What is a weed?
 Why worry about weeds in pastures and
landscapes?
Living n
 How weeds are regulated
 Weed biology
 Factors that lead to plant invasion
 Preventing invasion and spread of weeds
 Identifying weeds
 Control - mechanical, cultural, biological, and
chemical
 Common weeds in your area
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What’s a weed?
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UNCE, Reno, Nev.
Living n
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USDA-ARS
MSU Extension Service
1900: Arrived from Europe
I think I’ll settle
down here. This
looks like a good
place to raise a
family.
2000
Wow! The wide open continent of
North America offers great potential
for advancement.
1970
Way to go!
Today:
America, The Land of Opportunity
UNCE, Reno, Nev.
Invasive weed spread
Weed
Annual Spread
Reduced Grazing
Dyers woad
14%
38%
Canada thistle
10%
42%
Dalmation toadflax
8%
46%
Tall whitetop
9%
55%
Leafy spurge
12%
59%
Yellow starthistle
17%
65%
Spotted knapweed
24%
80%
UNCE, Reno, Nev.
Weed impacts
Decreased grazing
potential
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Economic losses
from refusals of hay
shipments
Decreased crop
yields
Cost of control
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UNCE, Reno, Nev.
Weed impacts
Decreased property
values
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Loss of wildlife and
fish habitat
Impairment of
wetland functions
Increased erosion
UNCE, Reno, Nev.
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Toxicity
Weed impacts
Increased habitat
for vermin such as
mosquitoes
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Impacts to
recreation
Altered fire regimes
Lowering of water
table depths
Etc….
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RGJ reader, Reno, Nev.
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How are weeds
regulated, and what are
your legal
responsibilities?
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The three D’s of noxious weeds
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Damaging to the economy or
environment
Difficult to control
Tend to Dominate a site
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How weeds grow
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Dicot
(Broadleaf)
•Two true leaves
•Broad leaves have
net-like veins
•Coarse tap root
Monocot
(Grass)
•One seed leaf
•Parallel veins
•Fibrous roots
Plant life cycles
Annual
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 One season for all
stages of
development
 Produce foliage,
flower seeds, then
die
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UNCE, Reno, Nev.
Yellow
starthistle
Plant life cycles
Summer annuals
 Live from spring to fall
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 Examples are foxtail, pigweed
Winter annuals
 Germinate in fall and winter
 Examples are cheatgrass and
mustard
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Plant life cycles
Biennials
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 Require two seasons for
completion of life cycle
 First year: develop roots and
low-growing leaves
 Second year: flowers, sets
seed and matures
 Examples are mullein and
musk thistle
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UNCE, Reno, Nev.
Musk thistle
Plant life cycles
Perennials
 Live more than two
years
UNCE, Reno, Nev.
Living n
 Will produce foliage,
seed, and reach
maturity year after year
 Examples are perennial
pepperweed and
Canada thistle
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Dandelion
Reproduction
Annuals and biennials
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 Seed
 Seed bank
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Reproduction
Perennials
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 Simple: Reproduce by seed and pieces of
root, such as dandelions
 Bulbous: Produce seed, bulblets and
bulbs, such as wild onion
 Creeping: Produce seeds, rhizomes
(underground stems), stolons (above
ground stems), or creeping roots
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Creeping roots of perennial
pepperweed
Living n
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UNCE, Reno, Nev.
Identifying weeds
Don’t be afraid to ask for help!
Living n
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Plant parts for
grass
identification
NRCS, Bozeman, Mont.
Plant parts for
broadleaf
identification
NRCS, Bozeman, Mont.
Have you correctly identified the
weed?
Perennial sowthistle
Spotted knapweed
Tumble
mustard
Are you really sure???
Yellow starthistle
Dandelion
How do weeds ensure their
success?
 They take advantage of the characteristics
of sites, including:
Living n
 Exposed or disturbed soil (grading road
shoulders)
 Turfgrass, range, pasture or groundcover that is
weakened by disease, pests, or poor
management
 Places where a desired species is not welladapted to its environment
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How do weeds ensure their
success?
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They are very competitive
 Grow well in spite of
interference from other plants
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UNCE, Reno, Nev.
How do weeds ensure their success?
They are
persistent
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 Will return year
after year
 Reproduce
vigorously
 Spread seeds
effectively
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UNCE, Reno, Nev.
How do weeds ensure their
success?
They are harmful
 Can alter the site
they grow in by
accumulating
salts, changing
water table
depths,
increasing
erosion,
increasing
wildfire
frequency, etc.
UNCE, Reno, Nev.
How do weeds spread?
Natural means
 Wind
Living n
 Water
 Animals
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UNCE, Reno, Nev.
How are we spreading weeds?
UNCE, Reno, Nev.
 Irrigation
 Roadside
shoulder work
 Construction/
fill dirt
 Vehicles
 Tillage
 Contaminated
seed or feed
 Livestock
management
What can we do?
Practice
Integrated Pest Management (IPM)
Living n
IPM is a sustainable approach to
managing pests that combines
biological, cultural, physical and
chemical tools in a way that
minimizes economic, health, and
environmental risks
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Hand
removal
of weeds
Living n
UC Davis
Sticky traps and
other physical traps
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Components of an IPM program
Planning
Setting action thresholds
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Monitoring and detection
Identification
Implementation
Evaluation
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ridall.com
IPM tools for weed management
(IWM)
Prevention
Eradication
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Mechanical controls
Cultural controls
Biological controls
Chemical controls
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Building a weed management plan
CONSIDER THE:
Identity of the weed
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Biology of the weed
Extent of the problem
Environmental conditions of the site
Ultimate objectives for the site
Most economical solution
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UNCE, Reno, Nev.
Method 1 of IWM:
Prevent the invasion and spread of weeds
Plant clean, weed-free seed
Avoid spreading weed seeds with manure
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Sanitize tillage and harvest equipment
prior to moving them from one field to
another
Plant and maintain desirable plant
species
Consider crop rotation to slow weed
spread
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Method 1 of IWM:
Prevent the invasion and spread of weeds
Minimize soil disturbance
and bare ground
Living n
Don’t overgraze pastures
Apply the appropriate
amount of water
Avoid driving in weedinfested areas
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USDA NRCS
Method 1 of IWM:
Prevent the invasion and spread of weeds
Don’t transport flowering plants that you
cannot identify
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Pull small patches before seed is formed
Carefully remove weeds that have
flowered
Report new infestations
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Reporting
State Weed Specialist, Department
of Agriculture
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Your local Cooperative Extension
office
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Method 2 of IWM:
Eradication
Removal of all weeds of a given species
from an area so they will not recur
unless reintroduced
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Must deplete seed bank of viable weed
seeds by controlling all seedlings
Only feasible for small, new invasions
Must revegetate the area
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Method 3 of IWM:
Mechanical Control
Cultivation
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Hoeing
Bulldozing
Burning
Hand pulling
Mowing
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CSUCE
UNCE, Reno, Nev.
Method 3 of IWM:
Mechanical control
Mulching
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Solarizing (use clear
plastic for maximum
affect)
Repeated tillage can
help reduce seed
populations
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UNCE, Reno, Nev.
Method 4 of IWM:
Cultural control
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Cultural control involves using
land management tools that
make it difficult for weeds to be
successful
 Shading
 Water and nutrient management
 Correct seeding rates
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Method 5 of IWM:
Biological control
Biological control is the
use of one organism to
suppress another
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 Can reduce pesticide use
 Agents can be free or
purchased
 Can effectively and
economically suppress
pests
 Does not eradicate a weed
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UNCE, Reno, Nev.
Method 5 of IWM:
Biological control
Characteristics of
successful biocontrol
agents:
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 Prolific
 Thrive and become
widespread in all habitats and
climates that the pest weed
occupies.
 Good colonizers of new
areas.
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NDOA
Leaf eating beetle
(Diorhabda elongata) on
tamarisk
Tamarisk biocontrol
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NDOA
Method 6 of IWM:
Chemical control
Living n
the Land
UNCE, Reno, Nev.
CSUCE
Manage pastures to minimize weeds
Herbicides
Managed grazing
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Prevention
Dense vegetation,
no bare spots
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Proper fertility
and species
USDA NRCS
Pesticides: an all-inclusive
term covering all “cides”
Herbicide
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Fungicide
Insecticide
Rodenticide
…
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Naming herbicides
Chemical name
 N-(phosphonomethyl)glycine
Living n
Common name
 Glyphosate
Trade or brand name
 RoundUp, Aquamaster,
Glypro, Rodeo, etc.
Brand
 Monsanto
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www.scotts.com
To spray or not to
spray?
Living n
the Land
To spray or not to spray?
Consider:
The goals for the site
The site conditions
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 Accessibility
 Proximity to surface water
 Depth to groundwater
 Presence of rare species
 Etc.
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Herbicide properties
Effectiveness against target species
Behavior in the environment
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Toxicity
Safety
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Twelve steps to follow before using
herbicides:
1. Identify the weeds
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2. Determine their life cycles
3. Consider all control
alternatives
4. Select the chemical based on
effectiveness, safety, and price
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Twelve steps to follow before
using herbicides:
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5. Read the label carefully and make
sure the herbicide is labeled for
the pest and the site
6. Determine the best time to apply
the chemical
7. Is the chemical restricted-useonly?
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Twelve steps to follow before
using herbicides:
Living n
8. Consider proximity to water,
nearby trees or shrubs, soil
composition, tendency to
contaminate water supplies
9. Check the weather
10. Have you read and do you have a
copy of the MSDS?
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More things to consider!
Living n
11. Are you applying the appropriate
amount by the best method?
12. Do you understand all necessary
safety requirements, and have you
followed them carefully? (gloves,
hat, eye protection, long sleeves,
long pants, shoes, etc.)
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Personal protective equipment
Living n
the Land
MU Extension
www.fadinap.org
What’s wrong with this picture?
Pesticide toxicity
Caution
Less toxic
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Warning
Danger
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More toxic
More things to consider!
UNCE, Reno, Nev.
Have you kept mixing and storage areas
away from waterbodies and wells?
Contain chemicals when
mixing
 Don’t mix on the same patch of soil
time after time
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 Try to mix on an impervious surface
 Be prepared
for spills
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Cleaning containers
 Check label for
directions
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 Follow triple-rinse
procedure
 Apply rinsate on
areas as indicated on
the label
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NEVER mix or rinse pesticides in the street!
UNCE, Reno, Nev.
Safety tips
Each time you use a pesticide, read the
directions!
Never eat, drink, or smoke while applying
pesticides or before cleaning up.
After applying pesticides, remove your clothes
and wash them; then thoroughly wash hands,
face, and body.
Safety tips
Work outdoors with good light and
ventilation when mixing or loading
pesticides.
Living n
Never mix or apply pesticides on windy
days.
If you splash or spill a pesticide while
mixing or loading, stop immediately.
Remove contaminated clothing and wash
thoroughly. Control, contain, then clean up
the spill.
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How do herbicides work?
Living n
Interfere with or disrupt biochemical
or physiological processes in
susceptible plants
Often affect a specific enzyme or
reaction
Example: amino acid inhibitors glyphosate
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Chemical control
Selective
Living n
 Kills only a specific
plant or type of plant
 Most common types
are broadleaf vs.
grass
ALWAYS READ AND FOLLOW
THE LABEL DIRECTIONS!
the Land
USDA NRCS
Chemical control
Examples of selective herbicides
 2,4-D (Weed-b-Gone, Weedar 64)
Living n
 picloram (Tordon, retricted use, persistent)
 chlorsulfuron (Telar, Glean; may be used preemergence)
 triclopyr (Garlon 3A)
ALWAYS READ AND FOLLOW THE
LABEL DIRECTIONS!
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Nonselective herbicides
Kills most or all of the vegetation in
the area covered
Living n
May be pre-mergent or postemergent
chemicals
ALWAYS READ AND FOLLOW THE
LABEL DIRECTIONS!
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Chemical control
Examples of nonselective herbicides
 glyphosate (Roundup)
Living n
 imazapyr (Arsenal; use pre-emergence
or postemergence; has a long residual in
high pH soil)
ALWAYS READ AND FOLLOW THE
LABEL DIRECTIONS!
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Herbicide Action
Preemergent herbicides
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Applied to soil
Kills plants as they
germinate and pick up
chemical in young
roots
Must be watered or
tilled in
May have some postemergent activity
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Postemergent herbicides
 Must be applied to living
plant tissue
 Little or no soil activity
Site of action
Living n
Contact Herbicide
Systemic Herbicide
 All parts of the plant
must be covered to
kill entire plant
 Applied to plant
tissue
 Usually quick acting
 Most often used for
annuals
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 Is translocated
through the plant to
the roots
 Takes time to work
 Used for perennials
Herbicide formulation
 How a product is packaged
 Active ingredients (to kill target plant)
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 Other ingredients (aid in application,
stability, absorption, inert ingredients)
 Liquid and dry formulations
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Spray adjuvants and surfactants
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 Added to spray mixes to
facilitate the mixing,
application, or effectiveness
of the herbicide
 Many herbicides require or
suggest surfactant use
 Some formulations already
include adjuvants (ex.:
Roundup Pro)
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Adjuvant types
Activators (enhance activity)
 Surfactants (nonionic, etc. – most widely
used)
 Oil adjuvants (petroleum oil concentrates)
Utility adjuvants
 Wetting agents (spreaders)
 Dyes
 Drift/foaming control agents
 pH buffers
 Water conditioners
 Etc.
Methods of application
 Foliar application
 Spot, wick, boom, aerial
 Basal bark/stump
application
 Soil application
What’s he doing
wrong?
Weed treatment in riparian areas
Select the most effective
treatment methods for the
site
Living n
If herbicides are used, be
sure the label allows
application adjacent to or
in the water
Consider wipe application
to minimize spray drift
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UNCE, Reno, Nev.
RESTRICTED USE PESTICIDE
(GROUND AND SURFACE WATER CONCERNS)
THIS PRODUCT IS A RESTRICTED-USE HERBICIDE DUE TO GROUND
AND SURFACE WATER CONCERNS. USERS MUST READ AND FOLLOW
ALL PRECAUTIONARY STATEMENTS AND INSTRUCTIONS FOR USE IN
ORDER TO MINIMIZE POTENTIAL FOR ATRAZINE TO REACH GROUND
AND SURFACE WATER.
Follow all
label
directions
GROUNDWATER ADVISORY
Atrazine can travel (seep or leach) through soil and can enter groundwater which may
be used as drinking water. Atrazine has been found in groundwater. Users are advised
not to apply atrazine to sand and loamy sand soils where the water table
(groundwater) is close to the surface and where these soils are very permeable, I.e.
well drained.
MIXING/LOADING INSTRUCTIONS
This product may not be mixed/loaded, or used within 50 ft. of all wells, including
abandoned wells, drainage wells, and sink holes. Operations that involve mixing,
loading, rinsing, or washing of this product into or from pesticide handling or
application equipment or containers within 50 ft. of any well are prohibited, unless
conducted on an impervious pad constructed to withstand the weight of the heaviest
load that may be positioned on or moved across the pad.
This product may not be mixed or loaded within 50 ft. of intermittent streams and
rivers, natural or impounded lakes and reservoirs. This product may not be applied
aerially or by ground within 66 ft. of the points where field surface water runoff enters
perennial or intermittent streams and rivers or within 200 ft. around natural or
impounded lakes and reservoirs. If this product is applied to highly erodible land, the
66-ft. buffer or setback from runoff entry points must be planted to crop, seeded with
grass or other suitable crop.
Groundwater
advisory
A 50-foot
distance from
well and water
bodies is
required
More to think about:
Are the conditions right for spraying?
Weather
Heat
Humidity
Dust
Wet plants
Timing is everything!
Early season
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Late pre-season
Season (bud or early flowering)
Post-frost
the Land
ALWAYS
read the
label and follow its
directions
Living n
the Land
Canada thistle (Cirsium arvense)
Sunflower
family
(Asteraceae)
Perennial
Dioecious
Reproduction
primarily
vegetative
through creeping
roots, some seed
Flowers white
to purple
www.wa.gov
www.wa.gov
www.ces.ncsu.edu
Canada thistle (Cirsium arvense)
Controls
Mechanical: Mowing can provide effective
control if conducted at one month intervals
Biological: One insect species available, but
only provides limited control
Fire: Controlled spring burns will slow spread
Chemical: Clopyralid + 2,4-D (Curtail),
picloram (Tordon), aminopyralid
(Milestone), chlorsulfuron (Telar), 2,4-D
Common crupina (Crupina vulgaris)
 Sunflower family
(asteraceae)
 Winter annual
 Also called
bearded creeper
 Resembles
knapweeds
 Grows to 4 feet
tall
 Urn-shaped
purple flowers
 Reproduces by
seed
Douglas Barbe, CDFA
Ray Gill, CDFA
Common crupina (Crupina vulgaris)
Controls
Mechanical: Hand pull, hoe, or till before
flowering; monitor site
Biological: No insects available; grazing
animals will avoid it
Chemical: Picloram (Tordon ), clopyralid,
triclopyr, 2,4-D + dicamba
Curly dock (Rumex crispus)
 Buckwheat family (Polygonaceae)
 Tap-rooted perennial
 Dark green alternate leaves
 Small green flowers turn reddish
brown at maturity
kaweahoaks.com
 Reproduces by seed (30,000
seeds/plant) or by root cuttings
www.psu.missouri.edu
Curly dock (Rumex crispus)
Controls
Mechanical: Prevent seed set; hand pull or
cultivate; mow to prevent flowering
Biological: Grazing not effective; no biocontrol
agents available
Cultural: Fertilize crops as needed
Chemical: 2,4-D or dicamba (Banvel) before
flower elongation; glyphosate (Roundup) at
early heading; aminopyralid (Milestone),
sulfometuron (Oust), clopyralid (Transline)
Dalmatian toadflax
(Linaria genistifolia spp. dalmatica)
 Figwort family
(Scrophulariaceae)
 Short-lived perennial
 Taproot
 Up to 5 feet tall
 Bright yellow flowers
with a spur
 Heart-shaped leaves
 Spreads by roots and
seed
UNCE, Reno, Nev.
Dalmatian toadflax
(Linaria genistifolia spp. dalmatica)
Controls
Mechanical: Hand-pull small plants, making sure to
remove lateral roots completely; mechanical controls
are not recommended for medium to large stands
Biological: Graze with sheep or goats to eliminate
seedlings; will not kill mature plants; eight insects in
use in the U.S.
Fire: Burning does not kill the roots and may stimulate
shoot growth
Chemical: Hybridization complicates chemical control;
try picloram (Tordon), picloram + 2,4-D; chlorsulfuron
(Telar), dicamba (Banvel); imazapic (Plateau)
Diffuse knapweed
(Centaurea diffusa)
Sunflower family (Asteraceae)
UNCE, Reno, Nev.
Biennial/short-lived perennial
Reproduces by seed only
 Flowers white to
pale purple
 Bracts
surrounding
flowers have
four or five
lateral spines
with one long
terminal spine
UNCE, Reno, Nev.
Diffuse knapweed (Centaurea diffusa)
Controls
Mechanical: Cutting, mowing, pulling
prior to seed set provides reduction,
but not elimination
UNCE, Reno, Nev.
Biological: Five insect species
Fire: Severe fire will effectively kill the plant
Chemical: Picloram (Tordon), clopyralid
(Transline), aminopyralid (Milestone),
imazapic (Plateau) 2,4-D, glyphosate
(Roundup)
Dodder
(Cuscuta
spp.)
USU
 Morningglory family
(Convolvulaceae)
CDFA
CSU
 Yellow to orange to
white twining plant
 Parasitic
 Especially problematic
on alfalfa
 Numerous small white
to pink flowers
 Annual; produces seed
Dodder (Cuscuta spp.)
Controls:
Mechanical: Mow, burn, remove infested
material. Destroy host plants. Use frequent
cultivation.
Cultural: Eliminate host plants
Biological: None
Chemical: Use Roundup (glyphosate) to kill
host plant; try imazethapyr (Pursuit),
pendimethalin (Prowl) or pronamide
(Kerb)
Downy brome (Bromus tectorum L.)
 Grass family (Poaceae)
 Winter annual
 Smooth erect stem; visible
ligule with frayed margin
 Reproduces by seed (up to
one billion/acre)
 Seeds are long and flat
with an awn as long as
the seed
 Mature plants turn
purple to brown as they
dry
 Increases fire frequency
UNCE, Reno, Nev.
UNCE, Reno, Nev.
Downy brome (Bromus tectorum L.)
Controls
Mechanical: Mow prior to seed set and repeat
as needed; hand pull small infestations
Biological: None available
Cultural: Graze to prevent seed set in spring;
reseed with competitive vegetation
Chemical: Glyphosate (Roundup) applied in
spring; imazapic (Plateau); preemergent,
such as Treflan or Oust, in fall or early
spring
Dyer’s woad
(Isatis tinctoria)
 Mustard family (Brassicaceae)
 Winter annual, biennial, or shortlived perennial
 Bluish-green alternate leaves
 Yellow flowers in
clusters with a flat
top
 Seeds produced in
seed pods near
mid-summer
Utah Weeds
Purdue
Dyer’s woad (Isatis tinctoria)
Controls
Mechanical: Hand-grub in rosette stage or
during flowering; mowing results in resprouting
Biological: Eurasian rust fungus stunts growth
Chemical: 2,4-D, chlorsulfuron (Telar),
metsufuron (Escort), imazapic (Plateau)
Eurasian watermilfoil
(Myriophyllum spicatum)
EWMF native
WA Dept. of Ecology





Water Milfoil family (Haloragaceae)
Submersed, rooted aquatic vine
7 to 10 feet long
Perennial
Leaves have 12 to 21 leaflet pairs vs.
fewer than 12 for native milfoil
 Leaves collapse when removed from
water
 Spreads by seeds and plant parts
UNCE, Reno, Nev.
Eurasian watermilfoil
(Myriophyllum spicatum)
Controls
Mechanical: Dredging, mowing, hand removal,
shading, bottom barriers. Will spread from
small plant fragments.
Cultural: Practice prevention; monitor boats
for contamination.
Biological: Milfoil weevil (not released in Nev.)
Chemical: 2,4-D, simazine, fluridone (Sonar;
maintain 10 to 20 ppb for 6 weeks), triclopyr
(Renovate 3)
Field bindweed (Convolvulus arvensis)
 Morningglory family
(Convolvulaceae)
 Perennial
 Alternate, arrowheadshaped leaves on
climbing stems
 Flowers are trumpetshaped and white to
pinkish
 Reproduces by seeds
which remain viable for
up to 50 years and from
rootstocks
UNCE, Reno, Nev.
Field bindweed (Convolvulus arvensis)
Controls
Mechanical: Pull vine to interrupt seed set; till
every two to three weeks during the growing
season for two to three years
Biological: Two moths are available
Cultural: Practice early detection and control
of small populations
Chemical: 2,4-D or dicamba (Banvel),
picloram (Tordon), metsulfuron (Escort),
imazapic (Plateau), glyphosate (Roundup)
Field horsetail (Equisetum arvense)
 Horsetail family
(Equisetaceae)
 Perennial
 Aerial stems
 Underground tuberbearing rootstocks
Purdue
 Stems are hollow and
jointed
 Does not flower;
reproduces by spores
Field horsetail (Equisetum arvense)
Controls
Mechanical: Prevent spore formation by
mowing or cutting; mulch; practice deep
cultivation
Biological: None
Fire: Rhizomes survive even hot fires
Chemical: Dichlobenil (Casoron), amitrole,
MCPA, chlorsulfuron (Telar)
Foxtail barley (Hordeum jubatum)
 Grass family (Poaceae)
 Perennial bunchgrass
 Leaf blades 1 to 6 inches
long
 Flower heads break into
seven-awned clusters of
three spikelets when
mature
UNCE, Reno, Nev.
 Reproduces by seed
www.anet.com
Foxtail barley (Hordeum jubatum)
Controls
Mechanical: Mow to prevent seed set
Biological: Graze early in the year
Cultural: Use good site-management
techniques; avoid overgrazing and bare
ground conditions
Chemical: Glyphosate (Roundup) or
preemergent herbicides
Hoary cress (Cardaria draba)
 Mustard family
(Brassicaceae)
 Perennial
 Small white flowers in flat
clusters
 Reproduces by seed and
creeping roots
UNCE, Reno, Nev.
Hoary cress (Cardaria draba)
Controls
Mechanical: Cultivation every 21 days
beginning early in spring and continuing until
no additional shoots or seedlings appear;
repeated disking
Biological: None known
Cultural: Plant competitive vegetation
Chemical: 2,4-D, imazapic (Plateau),
chlorsulfuron (Telar), or metsulfuron
(Escort)
Houndstongue
(Cynoglossum officinale)
NRCS, Bozeman, Mont.
www.invasive.org
agri.state.mt.us
 Borage family
(Boraginaceae)
 Biennial or short-lived
perennial
 Grows 1 to 4 feet tall
 Reddish-purple
flowers have 5 petals
 Leaves are hairy and
tongue-shaped
 Produces a single
flowering stem
 Reproduces by prickly
seed
Houndstongue
(Cynoglossum officinale)
Controls
Mechanical: Pull or dig; mow second year
plants during flowering but before seed
maturation
Biological: Currently being studied
Chemical: Picloram (Tordon), 2,4-D,
metsulfuron (Escort). chlorsulfuron (Telar),
imazapic (Plateau)
Johnsongrass
(Sorghum halepense)
 Grass family
(Poaceae)
 Most often perennial;
winter kill in cold
climates
 Grows 3 to 10 feet tall
 Leaves have
prominent, white
midvein
 Large, open reddish
panicles, up to 1 foot
long
 Spreads by seed and
rhizome
invasive.org
Johnsongrass
(Sorghum halepense)
Controls
Mechanical: Pull or dig; repeated, close
mowing can be effective; try fall plowing to
expose rhizomes to freezing temperatures
Biological: Managed grazing
Chemical: Glyphosate (Roundup),
sethoxydim (Poast), fluazifop (Fusilade
DX), imazapic (Plateau) with methylated
seed oil at late boot or bloom stage
Klamathweed (aka St. John’s wort)
(Hypericum perforatum)
 St Johnswort
family
(Clusiaceae)
 Perennial
 1 to 3 feet tall
 Transparent dots
on oblong leaves
 Yellow, fivepetaled flowers
 Spreads by seed
and creeping
stems
UNCE, Reno, Nev.
John Randall, TNC
Klamathweed (Hypericum perforatum)
Control:
Mechanical: Repeated hand pulling on new or
small infestations
Biological: Insects are available (Klamathweed
beetle, Chrysolina quadrigemina); weed is toxic
to horses
Cultural: Revegetate infested sites after control
Chemical: Apply glyphosate to actively growing
plants; 2,4-D to new seedlings (repeat
applications needed); metsulfuron (Escort®) in
pastures
Kochia (Kochia scoparia)
UNCE, Reno, Nev.
 Goosefoot family
(Chenopodiaceae)
 Annual
 1 to 8 feet tall
 Numerous narrow, hairy
leaves
 When dry, breaks off and
tumbles
Kochia (Kochia scoparia)
Control:
Mechanical: Mow just before seed set, cut, or
pull to interrupt seed production. Timing is
important.
Cultural: Avoid soil disturbance
Biological: None
Chemical: Most broadleaf herbicides are
effective, as is glyphosate
Leafy spurge (Euphorbia esula)
 Spurge family (Euphorbiaceae)
 Perennial
 Reproduces by seed and
extensive lateral root system
 Flowers yellowish-green, small,
and surrounded by paired,
heart-shaped yellowish-green
bracts
tncweeds.ucdavis.edu
CSUCE
tncweeds.ucdavis.edu
Leafy spurge (Euphorbia esula)
Controls
Mechanical: Cutting, mowing, tilling, pulling
ineffective
Biological: Thirteen insect species available;
sheep and goat grazing provides temporary
control
Fire: Ineffective due to regeneration from root
Chemical: Picloram (Tordon), 2,4-D,
glyphosate (Roundup), amitrole, dicamba,
imazapic (Plateau)
Meadow hawkweed
(Hieracium caespitosum)
 Sunflower family
(Asteraceae)
 Yellow flowers look
similar to a dandelion
flower, but are slightly
smaller and in clusters
 Perennial
Tom Forney, Oregon Dept. of Ag.
 Grows 1 to 3 feet tall
 Single stalk and leaves
are hairy
 Stems & leaves exude
milky sap when broken
 Spreads by root, stolon,
and seed
Tom Forney, Oregon Dept. of Ag.
E. Bella, USDA Forest Service.
Meadow hawkweed
(Hieracium caespitosum)
Controls
Mechanical: Not recommended; digging,
mowing, grazing or tillage stimulate growth of
new plants from fragmented roots, stolons and
rhizomes
Biological: None
Chemical: 2,4-D, dicamba, clopyralid
(Transline®), triclopyr & clopyralid (Redeem
R&P®), clopyralid & 2,4-D (Curtail®), picloram
(Tordon®), aminopyralid (Milestone®)
Mediterranean sage (Salvia aethopsis)
 Mint family (Lamiaceae)
 Biennial to perennial
 First year’s leaves are
grayish and wooly; plant
bolts in second season
with multi-branched stems
 Taproot
King Co. Weed
 Flowers are yellowishwhite
 Aromatic
 Reproduces by seed
spread as the plant
tumbles
CDFA
Mediterranean sage (Salvia aethopsis)
Controls
Mechanical: Cut the taproot 2 to 3 inches
below ground; mow repeatedly to reduce seed
production; tillage
Biological: Sage crown/root weevil
Cultural: Maintain healthy plant cover; avoid
overgrazing
Chemical: Picloram (Tordon 22K), clopyralid
(Transline), 2,4-D
Medusahead
(Taeniatherum caput-medusae)
 Grass family
(Poaceae)
 Winter annual
 Spike inflorence,
awns 1 to 4 inches
long, twisted,
minutely barbed
 Reproduces by seed
 Will outcompete
cheatgrass
UNCE, Reno, Nev.
Medusahead
(Taeniatherum caput-medusae)
Controls
Mechanical: Plowing/disking reduces stands by
50%-95% if conducted after germination
Biological: No insects; graze early in the season
Fire: Slow, hot fires can reduce a stand by 60%95%
Chemical: Glyphosate (Roundup), imazapic
(Plateau), sulfometuron methyl (Oust)
Musk thistle (Carduus nutans)
 Sunflower family
(Asteraceae)
 Biennial
 Winged stem
 Leaves have
prominent, lightcolored midrib
 Flowers deep rose,
violet, or purple
 Reproduces by seed
 Average seed
production 10,000
seeds/plant
 Seed can be viable
for 10 years
UNCE, Reno, Nev.
Musk thistle (Carduus nutans)
Controls
Mechanical: Repeated mowing, hand pulling,
or cutting can stop spread
Biological: Thistle head weevil; thistle crown
weevil
Chemical: 2,4-D, dicamba (Banvel),
glyphosate (Roundup), clopyralid
(Transline), picloram (Tordon),
chlorsulfuron (Telar), or aminopyralid
(Milestone )
Oxeye daisy
(Chrysanthemum leucanthemum)
 Sunflower family
(Asteraceae)
 Perennial
 Grows 1 to 3 feet
tall
 Spreads by seed;
26,000 seeds from
a single plant!
 Smaller flower
than ornamental
Shasta daisy
UNCE, Reno, Nev.
Oxeye daisy
(Chrysanthemum leucanthemum)
Controls
Mechanical: Hand pull or dig; remove entire
root mass and repeat
Cultural: Don’t plant as an ornamental; read
labels on seed mixes
Chemical: Aminopyralid (Milestone),
clopyralid (Transline), glyphosate on actively
growing plants (repeat)
Perennial sowthistle
(Sonchus arvensis)
 Sunflower family
(Asteraceae)
 Perennial
 Grows 2 to 4+ feet tall
 Erect, hollow stems with
milky sap
J. DiTomaso, UCD
 Leaves have prickly margins
OSU
 Yellow flowers
 Seeds spread by wind; also
spreads from creeping roots
NDSU
Perennial sowthistle (Sonchus arvensis)
Controls
Mechanical: Cultivate below 30 cm when plants
are in rosette stage; till repeatedly
Biological: Insects and nematodes; cattle and
sheep will graze the weed
Fire: Kills top growth but does not kill the roots
Chemical: 2,4-D, clopyralid + 2,4-D (Curtail),
triclopyr + clopyralid (Redeem R&P),
aminopyralid (Milestone ), amitrole
Perennial pepperweed
(Lepidium latifolium)
 Mustard family
(Brassicaceae)
 Perennial
 Prefers moist,
alkaline soils
UNCE, Reno, Nev.
 Lanceolate
leaves; upper
leaves are smaller
 White flowers
produced in June
to September
UNCE, Reno, Nev.
 Reproduces by
seed and
creeping roots
Perennial pepperweed
(Lepidium latifolium)
Controls
Mechanical: Avoid mowing, cultivation and
plowing; try repeated hand-pulling for 4+ years
Biological: Research being done on insects;
graze intensively using sheep or goats; will not
kill the weed, however
Chemical: 2,4-D amine; metsulfuron (Escort)
or chlorsulfuron (Telar); imazapyr (Arsenal,
Habitat), imazapic (Plateau)
Plumeless thistle (Carduus acanthoides)
 Sunflower family
(Asteraceae)
 Winter annual or biennial
 Mature plants are 1 to 4
feet tall
 Hairs on underside of leaf
WI DNR
 Leaf-like spines on stem
 Single flower at end of
stem
 Purple flower heads 1 to 2
inches in diameter
 Thick, fleshy taproot
 Spreads by seeds
OR Dept. of Agriculture
Plumeless thistle (Carduus acanthoides)
Controls
Mechanical: Pull or dig plants, removing top 2
inches of root; mow closely twice per season;
do not let seeds form
Biological: Thistle head weevil; thistle crown
weevil
Chemical: 2,4-D, dicamba, glyphosate,
clopyralid (Transline), picloram (Tordon),
chlorsulfuron (Telar), or aminopyralid
(Milestone)
Poison hemlock (Conium maculatum)
 Parsley family (Apiaceae)
 Biennial; may grow to 9 feet tall
 Tiny white flowers form an umbel
 Distinctive purple splotches on
hollow stems
 Tap-rooted
 Reproduces
by seed
Purdue
 Highly
poisonous,
especially
taproot
Purdue
Poison hemlock (Conium maculatum)
Controls
Mechanical: Mow prior to seed production;
hand pull while wearing gloves
Biological: Hemlock moth (defoliates)
Chemical: 2,4-D, MCPA, picloram (Tordon),
glyphosate (Roundup) or metsulfuron
(Escort); use water-labeled formulation in
riparian area
Puncturevine (Tribulus terrestris)
 Caltrop family
(Zygophyllaceae)
 Annual
 Reproduces by seed
 Can grow 15+ feet
across
 Yellow flowers occur
every few inches along
stems
 Fruits sharp pointed,
five segments, each
section contains 2 to 4
seeds
UNCE, Reno, Nev.
Puncturevine (Tribulus terrestris)
Controls
Mechanical: Dig, hoe, till, hand pull prior
to seed production; mulch 4 to 6 inches
deep
Biological: Two effective insect species
available
Chemical: 2,4-D, glyphosate (Roundup,
etc.), imazapic (Plateau), chlorsulfuron
(Telar) preemergents
Purple starthistle (Centaurea calcitrapa)
 Sunflower family
(Asteraceae)
 Biennial, rarely annual
 Flowers purple with one inch
spines
 Reproduces by seed
CDFA
 Seed can be viable for many
years
 Seedheads break off easily
King Co. Weed
Purple starthistle (Centaurea calcitrapa)
Controls
Mechanical: Hand pulling can remove small
infestations, mowing alone is ineffective
Biological: Five insect species available;
repeated grazing (cattle/sheep) can be an
effective control
Fire: May provide control if burned prior to seed
set for multiple years
Chemical: 2,4-D, picloram (Tordon), clopyralid
(Transline), triclopyr + clopyralid (Redeem
R&P), dicamba
Purple loosestrife (Lythrum salicaria)
 Loosestrife family
(Lythraceae)
 Perennial
 Flowers purple on
spikes; stems are
square
 Reproduces by
seed and
adventitious roots
TNC Weeds
 Average seed
production is 2.5
million seeds/plant
 Seed can be viable
for several years
Purple loosestrife (Lythrum salicaria)
Controls
Mechanical: Dig young plants, taking care to
remove all root fragments
Biological: Several insects available
Chemical: Glyphosate in water-labeled
formulation (Rodeo), triclopyr (Renovate),
imazapyr (Habitat), metsulfuron (Escort)
Quackgrass (Elytrigia repens L.)
 Grass family (Poaceae)
 Perennial
 1 to 3 feet tall
 Leaf blades ¼ to ½ inch
wide, flat, and pointed
 Upper surface of leaf
blade may be hairy
Univ. of Illinois
 Leaves often constricted
near tips
 Florets are awnless, or
have short, straight awns
 Reproduces by seeds and
spreading, sharp-pointed
rhizomes
Quackgrass (Elytrigia repens L.)
Controls
Mechanical: For small infestations, pull or dig;
try repeated plowing, mowing, or disking
followed by herbicide application
Biological: No insects; graze prior to other
controls
Chemical: Glyphosate (Roundup), fluazifop
(Fusilade DX), bromacil + diuron (Krovar),
amitrole, pronamide (Kerb), dichlobenil
(Casoron)
Russian knapweed (Acroptilon repens)
 Sunflower family (Asteraceae)
 Perennial
 Flowers are lavender to pink to
white
 Flowers from
June to August
 Reproduces by
seeds and
creeping roots
UNCE, Reno, Nev.
Russian knapweed (Acroptilon repens)
Controls
Mechanical: Cutting or mowing prior to seed
set provides reduction, but not elimination
Biological: One insect species
Chemical: Picloram (Tordon), clopyralid
(Transline), aminopyralid (Milestone),
imazapic (Plateau), 2,4-D, glyphosate
(Roundup)
Russian thistle (Salsola tragus)
 Goosefoot family (Chenopodiaceae)
 Annual
 Bushy, ½ foot to 3 feet tall, with
many branches
 Red or green flowers
 Reproduces by seed; seed spreads
as plants break off and tumble,
hence name “tumbleweed”
 Spreads by seeds
UNCE, Reno, Nev.
Russian thistle (Salsola spp.)
Controls
Mechanical: Mow or hoe at early stages of
growth; cultivate; pull seedlings
Cultural: Prevent soil disturbance (not a
very competitive plant)
Biological: None
Chemical: Most broadleaf herbicides are
effective, as is glyphosate as a spot spray;
apply herbicides to early growth; use
preemergents from March to May
Rush skeletonweed
(Chondrilla juncea)
 Sunflower family
(Asteraceae)
 Tap-rooted perennial
 Grows 1 to 4 feet tall
 Look for downwardlybent coarse hairs on
the base of stems
 Stems above are
smooth
 Leaves are almost
invisible except in
rosette
 Flowers are yellow and
less than one inch wide
 Spreads by seed and
roots
J. DiTomaso, UC Davis
Rush skeletonweed
(Chondrilla juncea)
Controls
Mechanical: Hand-pull small plants repeatedly
when young; do not mow or cultivate
Biological: A rust and two insects are available;
try sheep grazing
Fire: Burning probably will not kill the roots and
may stimulate shoot growth
Chemical: Picloram (Tordon), clopyralid
(Transline), MCPA, 2,4-D
Scotch thistle (Onopordum acanthium)
 Sunflower family
(Asteraceae)
 Biennial
 Grows to 8 feet
tall
 Winged stems
 Leaves are large,
hairy, and have a
grayish-green,
cottony look
 Prominent midvein
 Flowers pale
purple to violet
 Spreads by seed
UNCE, Reno, Nev.
USU Extension
Scotch thistle (Onopordum acanthium)
Controls
Mechanical: Pull, dig or remove top 2 inches of
crown before seed set; mowing does not kill the
plant and it may still flower
Biological: No insect species available, cattle and
sheep will not graze scotch thistle
Cultural: Plant competitive grasses; avoid
overgrazing
Chemical: 2,4-D, dicamba, glyphosate, clopyralid
(Transline), picloram (Tordon), chlorsulfuron
(Telar ), or aminopyralid (Milestone)
Spotted knapweed (Centaurea maculosa)
 Sunflower family
(Asteraceae)
 Short-lived perennial,
rarely biennial
 Reproduces by seed
tncweeds.ucdavis.edu
 Flowers pinkish-purple,
rarely cream
 Floral bracts tipped with
dark comb-like fringe
CSUCE
UNCE, Reno, Nev.
Spotted knapweed (Centaurea maculosa)
Controls
Mechanical: Cutting or mowing, prior to seed set
provides reduction, but not elimination
Biological: Thirteen insect species; cattle, sheep or
goat grazing useful in reduction
Fire: Variable effects, depending on severity of fire
Chemical: Picloram (Tordon), clopyralid
(Transline), aminopyralid (Milestone), imazapic
(Plateau) 2,4-D, glyphosate (Roundup)
Sulfur cinquefoil (Potentilla recta)
 Rose family
(Rosaceae)
 Perennial
 1 to 1½ feet tall
 Hairy stems
 Toothed
leaflets
King Co., WA
 Light yellow
flowers with
five notched
petals
J. DiTomaso, UC Davis
 Spreads by
seed and
shoots
Sulfur cinquefoil (Potentilla recta)
Controls
Mechanical: Dig, hand-pull or till repeatedly,
prior to seed production; mowing results in
prostrate growth form
Biological: Several insects are currently being
investigated
Chemical: Picloram (Tordon), metsulfuronmethyl (Escort), aminopyralid
(Milestone), 2,4-D
Tamarisk (Tamarix ramosissima, others)
 Tamarisk family
(Tamericaceae)
 Perennial
 Shrubby tree 5 to
20 feet tall
 Reddish-brown
bark and pink to
white flowers
 Leaves are small
and scale-like
 Reproduces by
seed and
adventitious roots
UNCE, Reno, Nev.
Tamarisk (Tamarix ramosissima, others)
Controls
Mechanical: Burn prior to herbicide
application to prepare the site; will sprout if
cut; dig out with bulldozer (not very
effective, as root fragments sprout)
Biological: Leaf-eating beetle has been
released in Nevada and Utah
Chemical: Imazapyr (Arsenal), triclopyr
(Garlon or Renovate), glyphosate in
water-labeled formulation (Rodeo)
Yellow starthistle (Centaurea solstitialis)
 Sunflower family
(Asteraceae)
 Winter annual
 Flowers yellow
with 1 inch
spines
 Reproduces by seed
UNCE, Rneo, Nev.
 Average seed production is 1,000
seeds/plant
 Seed can be viable for several
years
Yellow starthistle (Centaurea solstitialis)
Controls
Mechanical: Hand pulling can remove small
infestations, mowing alone is ineffective
Biological: Five insect species available; repeated
grazing (cattle/sheep) can be an effective control
Fire: May provide control if burned prior to seed set
for multiple years
Chemical: 2,4-D, picloram (Tordon), clopyralid
(Transline), aminopyralid (Milestone),.
chlorsulfuron (Telar), triclopyr + clopyralid
(Redeem R&P)
Yellow toadflax (Linaria vulgaris)
 Figwort family
(Scrophulariaceae)
 Perennial
 Taproot
 1 to 2 feet tall
 Narrow leaves
 Bright yellow
flowers with
bearded orange
throat
 Spreads by roots
and seed
Yellow toadflax (Linaria vulgaris)
Controls
Mechanical: Hand-pull small plants, making sure to
remove lateral roots completely; mechanical controls
are not recommended for medium to large stands
Biological: Graze with sheep to eliminate seedlings;
will not kill mature plants; eight insects in use in the
U.S.
Chemical: Hybridization complicates chemical
control; picloram (Tordon), picloram + 2,4-D,
chlorsulfuron (Telar), dicamba, imazapic (Plateau),
glyphosate (Roundup or Rodeo, depending on
the presence of surface water)
Now what?
Go home and inventory the weeds on your
property
Living n
Identify the weeds
Why do you have a weed problem? What
can you change about the way you manage
your property that will decrease the weed
population?
the Land
Then...
Determine the most appropriate
controls based on biology of the weed
and your plans for the site
Living n
Fill out your weed management plan
activity sheet
Start working!
Monitor your property for weeds on a
continual basis
the Land
Successful weed management
requires constant vigilance and care
on the part of the land manager.
CSUCE