United States Department ofAgriculture

Field Guide for Managing

Yellow Starthistle

in the Southwest

Forest 

Service

Southwestern

Region TP-R3-16-07 Revised June 2017
Cover Photos

Top left: Steve Dewey, Utah State University, Bugwood.org 

Top right: Steve Dewey, Utah State University, Bugwood.org 

Left center: Steve Dewey, Utah State University, Bugwood.org 

Bottom left: Cindy Roche, Bugwood.org

Bottom right: USDA Forest Service

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1 

Yellow starthistle (Centaurea solstitialisL.) 

Sunflower family (Asteraceae)

Yellow starthistle is an invasive plant that has been listed

as a noxious weed in Arizona and New Mexico. Thisfield

guide serves as the U.S. Forest Service’srecommendations

for management of yellow starthistle in forests, woodlands,

rangelands, and deserts associated with its Southwestern

Region. The Southwestern Region covers Arizona and

New Mexico, which together have 11 national forests. The 

Region also administers 4 national grasslands located in 

northeastern New Mexico, western Oklahoma, and the

Texas panhandle.

Description

Yellow starthistle (synonyms: golden starthistle, St.

Barnaby’s thistle, yellow cockspur) is an early maturing

winter annual. Native to Eurasia, it was introduced into

North America as a seed contaminant in the mid-1850s and 

has persistently spread across the western United States. 

Yellow starthistle is similar in appearance to two closely 

related species: C. melitensis (Malta starthistle) and C. 

sulphurea (Sicilian starthistle).

Growth Characteristics

• Grey-green to blue-green herbaceous plant covered 

in fine, white cottony hairs; winter annual and 

occasional biennial. 

• Stout, rapidly growing, vigorous taproot; may grow 

deeper than 36 inches.

• Germinates fall to spring; rosette in fall/winter,

deeply lobed leaves with fine, cottony hairs appear 

ruffled; bolts May to June with stiff, openlybranched stems, 6 to 60-inches tall with large stem

wings.

• Leaves alternate, linear to oblanceolate; margins 

smooth, toothed, or wavy. 

• Flowers May to December, yellow flowers borne at 

tips or in axils of winged stems; flower heads with 

spiny bracts form in June or July; each bract has a 

central spine up to 2 inches long with 2 to 3 pairs of 

lateral spines.

• Reproduces solely via seed; two types of smooth 

seed—one type is lighter in color with a pappus of 

barbed bristles, the other is darker without a pappus.

• Leaves and stem become straw colored as seeds 

form; flower head becomes straw colored when seeds

are mature; seeds are viable for up to 10 years.

Ecology

Impacts/Threats

Yellow starthistle is highly competitive and often develops 

dense, impenetrable stands that lower the diversity of 

desirable flora and fauna species. The presence of sharp, 

long spines on seed heads of yellow starthistle degrades

livestock grazing, wildlife habitat, and recreational

opportunities. When forced to graze mature yellow 

starthistle, livestock (especially horses) can be affected by 

an incurable neurological disorder known as “chewing 

disease.” A neurotoxic sesquiterpene lactone in starthistle

species called repin is believed to be the underlying cause 

of the disorder. However, animals typically avoid the weed

because of the sharp spines and hairs.

Site/Distribution

Yellow starthistle prefers well-drained soils, hot dry 

summers, and 10 to 60 inches of precipitation. It occurs in 

open areas in woodlands, desert scrub, chaparral,

rangeland, pastures, waste areas, cropland, and roadsides 

that generally lie below 7,500 feet in elevation. It is also 

common around residential subdivisions, agricultural land,

and recreation areas. The species is found in foothill areas

of southwestern New Mexico and elsewhere in deserts, 

uplands, rangelands, and mountains of the Southwest.

Spread

When unassisted, yellow starthistle seed rarely moves far 

from the parent plant. However, seed readily attaches to

fur, hair, or clothing. The seed can be transported afar by 

adhering to tires and undercarriages of road vehicles and

equipment. The seed may also be introduced into new 

areas through transported hay that is not certified to be 

weed free. 
2

Invasive Features

Yellow starthistle is a prolific seed producer and in dense 

stands can produce 50 to 100 million seeds per acre. It 

grows rapidly and is highly adaptable to environmental 

variation. This allows yellow starthistle to out-compete

native plant species for sunlight, space, water, and 

nutrients. Other features that facilitate invasiveness include 

a deep taproot that accesses available soil moisture, 

winged stems that dissipate heat, and formidable spines at 

maturity that deter grazing by livestock or wildlife.

Management

Due to its abundant seed production, early detection and 

eradication of yellow starthistle soon after discovery 

increases the chances for successful control. A 

commitment to repeated management actions is a must, 

and a combination of methods and repeated treatments will 

improve effectiveness. The following actions should be 

considered when planning a management approach to 

controlstarthistle:

• Maintain healthy plant communities to suppress or 

limit the impact of a starthistle infestation.

• Incorporate sound grazing management with any 

control strategy.

• Combine mechanical, cultural, biological, and 

chemical methods to control yellow starthistle

populations whenever possible.

• Include monitoring and a follow-up treatment plan 

for missed plants and seedlings.

• Map large infestations and keep annual records of 

reported infestations.

Table 1 summarizes management options for controlling 

yellow starthistle under various situations. Further details

on these management options are explained below. Choice

of individual control method(s) for starthistle depends on

many local factors including the extent of infestation, 

current land use, and site conditions (terrain, accessibility 

for treatment, microclimate, presence of non-target flora 

and fauna, etc.). Other important considerations include 

treatment effectiveness, overall cost, and the number of

years needed to achieve control. Typically, more than one

control method may be needed for a particular site.

Physical Control

Yellow starthistle reproduces solely by seed, so physical

methods should focus on reducing seed production and

preventing seed germination. These methods usually have

to be repeated and must be properly timed to be effective.

Manual Methods

Hand pulling or hoeing are most effective in a maintenance

program for an area where yellow starthistle isrelatively

sparse. Take care to remove as much of the taproot as 

possible. Anticipate that hand removal will need to be

repeated in about 2 weeks to remove missed plants or

those maturing at a later time. Care should be taken to

minimize soil disturbance and to properly dispose of plant 

debris by bagging and/or burning.

Mechanical Methods

When using machinery to manage yellow starthistle, the 

equipment should be cleaned after use to prevent 

movement ofseed into un-infested areas.

Tillage – In suitable terrain, tillage in early summer with a 

plow or disc that is repeated at a later time (about 4 to 6 

weeks) can effectively bury yellow starthistle plant parts. 

A harrow or drag pulled behind a tractor can be used to cut

and separate shoots from roots of larger mature plants.

These methods are most commonly used in agronomic or

roadside settings and should only be used when the soil 

surface isdry since fragmented plant segments in moist 

soils will regrow and possibly magnify the problem.

Mowing – Mowing is commonly used for yellow

starthistle along roadsides and in recreational areas. 

Although it can be a cost-effective method for starthistle 

control, mowing is not feasible in many locations due to 

rocks or steep terrain. Some vegetation management 

experts do not recommend mowing since plants not cut 

closely to the surface often produce side branches that can 

form additional flowers, even with repeated mowing and 

proper timing. 

Despite its limitations, mowing over a 3-year period has 

been reported to provide over 90 percent control when two 
3 

Table 1. Management options*

Site Physical Control Cultural Control Biological Control Chemical Control

Roadsides Use repeated, shallow cultivation 

and/or mowing throughout 

germination and growing periods.

Use seed and mulch certified to 

be weed-free. Gravel and other 

road materials transported into 

un-infested areas should be weed

free.

Educate road crews to identify

and report infestations along 

roads; implement requirements 

for vehicle operations in infested

areas.

Consider using flies, 

weevils, or rust fungus as

classical biocontrol agents 

(see table 2). Usefulness

of biocontrol agents may

be limited due to possible 

disturbances in agent life

cycles from roadside

operations.

Use truck spraying

equipment to apply

herbicide during early

growth. Clean equipment

to prevent spread.

Rangeland Use repeated, shallow cultivation 

and/or mowing throughout 

germination and growing periods.

If feasible, combine prescribed 

fire with herbicide spraying.

Use seed and forage hay certified 

to be weed-free; use pellets for 

horses in backcountry areas.

After passing through infested

areas, inspect and remove any 

seed from animals, clothing, and

vehicles before entering treated 

or un-infested areas.

Use prescribed grazing

during spring with an

intense, short-duration 

approach in combination 

with other control

methods. Closely manage

grazing to prevent

overuse.

Consider using flies, 

weevils, or rust fungus as 

classical biocontrol agents 

(see table 2). 

For extensive and dense 

infestations, use ground or 

aerial broadcast spraying.

For less dense 

infestations, consider 

ATV or backpack

spraying. Clean ground

equipment to prevent

spread.

Wilderness 

and other

natural

areas

Hand methods can be used by

starting at the edges of an

infestation and working toward

the center. Pull before plant 

reaches full bloom.

Use seed and forage hay certified 

to be weed-free; use pellets for 

horses in backcountry areas.

After passing through infested

areas, inspect and remove any 

seed from animals, clothing, and

vehicles before entering treated 

or un-infested areas.

Post signs warning visitorsto

inspect for and remove seeds.

Same as above. Use backpack or handheld sprayers. Broadcast

spraying by aerial or 

ground methods may be

used on thicker stands if

allowed. Clean ground 

equipment to prevent

spread.

* Choice of a particular management option must be in compliance with existing regulations for the land resource.

timely, repeated mowings are made per year. Since timing 

is critical, best results occur when mowing is completed in 

the early flowering stage before viable seed production, 

i.e., when no more than 2 to 5 percent of the spiny heads 

are in bloom. After mowing, no leaves should be left 

below the level of the cut.

Prescribed Fire

Burning from January to May can eliminate yellow 

starthistle in the seedling to early bolting stages. However, 

burning during this time is often limited since there 

generally is insufficient fine, dry fuel available to carry the 

starthistle may also be burned in early to mid-summer (late 

intense, uniform fire required for starthistlecontrol. Yellow

May to early July) during the early flower stage. Despite 

its effectiveness in selected situations, risks associated with 

burning should be thoroughly assessed in a specific 

management plan for prescribed fire. 

Cultural Control

Educational programs focused on the biology and 

identification of nonnative weed species should be

sponsored for local land managers and others to help find,

report, and monitor suspected infestations. Vehicles, 
4

humans, and livestock should be discouraged from

traveling through infested areas. A program to check and 

remove seed from vehicles and livestock should be 

implemented to help stop dispersal. Hay, straw mulch, 

seeds for planting, and other similar materials should be 

certified to be weed free before use in unaffected areas or 

areas previously treated for starthistle. Gravel and other 

road materials transported into un-infested areas should 

also be weed free.

Biological Control

Grazing

In California, properly timed spring grazing with cattle, 

goats, or sheep has been shown to reduce yellow

starthistle’s growth, canopy cover, survivability, and

reproductive capacity. This approach is based on intensive

livestock grazing of yellow starthistle after stems on 

rosettes have begun to bolt but before spiny seed heads 

develop. Cattle and sheep avoid starthistle once the flower 

heads produce spines, whereas goats continue to browse 

plants even during the flowering stage. For this reason, 

goats are popular for controlling yellow starthistle in

relatively small infestations.

Although grazing can reduce starthistle presence, owners 

of horses and other livestock should ensure that suitable 

alternative forage is available. Owners should also look for 

signs of toxicity or so-called “chewing disease” in 

starthistle stands that have flowering heads. Prescribed 

grazing with an intensive, short-duration approach can be 

part of an effective control strategy to manage starthistle, 

especially when combined with other control methods (see 

“Integrated Control Methods” at the end of this section for 

more information). A system using short periods of intense 

livestock grazing has been adopted in other countries for 

starthistle control. In this system, infested pastures are 

intensively grazed for 3 to 5 days, often by using electric 

fencing. After livestock have been moved to another part 

of the pasture, the grazed area is allowed to recover for at 

least a month before grazing is repeated. The system 

typically results in more uniform and complete forage 

utilization. In addition, desirable forage is not completely 

grazed and can rapidly recover. Ultimately, this increases

seasonal forage production and stocking capacity.

Classical Biological Control

Control with classical biocontrol agents (insects, 

pathogens, etc.) is most suitable for sites where other 

control methods are impractical. Biocontrol agents should 

be used only if infestations are large enough to sustain

agent populations. Needs of the biocontrol agent should be 

considered before implementing other weed treatments.

USDA-approved biocontrol agents listed in table 2 have 

been found to establish well in the western United States 

and contribute significantly to reduce seed production. 

Several biocontrol agents have been released in Arizona 

and New Mexico for control of yellow starthistle, but 

experience with these agents is still limited. For further 

information on biocontrol of yellow starthistle, see Wilson 

et al. (2003) in the “References and Further Information” 

section of this field guide.

Organisms (insects, pathogens, etc.) used as biocontrol 

agents in southwestern States should be adaptable to arid 

environments and local conditions. Public, tribal, and 

private land managers may obtain biocontrol agents for 

release directly from local offices of the USDA Animal 

and Plant Health Inspection Service (APHIS) when these 

agents are available. Other sources for biocontrol agents 

include locally developed insectaries or private companies.

A permit must be obtained from APHIS before biocontrol 

agents can be transported across State lines. Regulations 

and permit applications (PPQ 526 permit forms) pertaining 

to interstate shipment of biocontrol agents can be found at 

https://www.aphis.usda.gov/aphis/ourfocus/planthealth/im

port-information/permits/regulated-organism-and-soilpermits/sa_apply/ct_plantpest_howtoapply. Although 

biocontrol agents may be collected and released internally 

in a given State without an APHIS permit, the State’s 

department of agriculture or agricultural extension service 

should be consulted for any regulations relating to 

movement of these agents within the State.

Chemical Control

Yellow starthistle is best controlled with a selective, postemergent, broadleaf herbicide since these chemicals have 

little or no effect on grass species. The primary entry point 

for herbicide into the plant is through the leaves with only
5

Table 2. Classical biocontrol agents approved for yellow starthistle

Species Type of

Agent

Site of

Attack Impact on Host Use/Considerations forRelease

Bangasternus 

orientalis

weevil Flower buds/ 

seed heads

Larval feeding in the head can reduce the 

number of seeds by 40 to 60 percent.

B. orientalis is a good flier and 

disperses well. It is difficult to 

establish at sites where E. villosus is 

already established.

Chaetorellia 

australis

fly seedheads Internal larval feeding reduces the number of 

developing seeds in the bud by 80 to 100 

percent.

Disperses very well, thus it is 

widespread in most areas it was 

established. 

Eustenopus

villosus

weevil Young 

flower buds 

and 

seedheads

Adult feeding and oviposition can destroy 

young buds, which appear as brown, dry and 

tilted heads. Larval feeding in the head can 

reduce the number of seeds by 90 to 100 

percent.

It is now widely established in 

California, Oregon, Washington and 

Idaho and is abundantly available for 

collection and redistribution.

Larinus curtus weevil Pollen, 

flowers, 

seedheads

Adult feeding on pollen and flowers does 

little to damage the plant; larval feeding in 

seed heads results in seed reduction of 75 to 

100 percent.

L. curtus is a strong flier and is 

expected to disperse well on its own.

Urophora 

sirunaseva

fly Seedheads Internal larval feeding reduces the number of 

developing seeds in the head by about 50 

percent. Heads infested with this gall fly 

produce fewer seeds than heads infested 

with Chaetorellia flies.

The presence of high densities of U. 

sirunaseva at a site does not appear to 

interfere with survival of other seed

head-infesting agents.

Puccina jaceae

var.solstialis

rust fungus leaves and

stem

Stress caused by agent reduces production of 

flower heads and seed.

Released in 2004 in California, the 

rust has not demonstrated a strong 

record of persistence

minor entry through roots.

All herbicides shown in table 3 will effectively control 

yellow starthistle when properly applied. Of the 

compounds recommended, picloram and clopyralid are

the most commonly used since they provide some 

residual activity in the soil and will controlseedling 

emergence for a few months after spraying. Aquatically 

approved herbicide formulations and surfactants must

be used in or near water. Each herbicide product has

specific requirements and restrictions; therefore, it is 

important to read the label carefully and follow all

instructions when mixing and spraying.

Herbicide Application

The most effective time to spray yellow starthistle is 

usually late autumn to early spring during the seedling

to rosette stage. Spraying is also effective later in spring 

when plants have 4 to 6 inches of growth and good 

growing conditions exist. Since yellow starthistle is an

annual, it should not be sprayed during or after

flowering as these treatments will be ineffective. 

Yellow starthistle establishment is closely tied to 

rainfall events, which can complicate herbicide 

spraying. New plants can be produced throughout the 

year, and propagation from year to year can be highly

variable. Therefore, infested areas should be checked 

closely for seedling abundance before deciding to spray.

Herbicides may be applied by backpack or hand-held 

sprayers, ATV or UTV sprayers, or conventional boom 

sprayers that are pulled or attached to a tractor or truck.

Aerial application via fixed-wing airplane or helicopter 

may be warranted for large, monotypic infestations. 

Any equipment used to spray herbicide should be 

calibrated. Because herbicides listed in table 3 may 

impact desirable broadleaf and woody species, 

precautionary measures should be taken if nontarget 

species need to be protected.
6

Table 3. Herbicide recommendations

Common

Chemical Name

(active ingredient)

Product

Example(s)1

Broadcast 

Treatment

(rate per acre)

Spot Treatment 

(spray solution)2

Time of

Application Remarks

Clopyralid Reclaim 

Stinger 

Transline

0.25–0.67 pints 1–3% Fall to early spring

during early rosette

stage.

Selective broadleaf herbicide.

Most perennial grasses are

tolerant; residual.

Clopyralid + 2,4-D3 Curtail 0.25–1 pint 1–3% After most rosettes

have emerged, but

before flower heads

form.

Same as above.

Aminocyclopyrachlor

+ chlorsulfuron

Perspective 3–4.5 ounces Consult label for 

spot applications.

Lower rate for 

rosette; higher rate 

at bolting. Fall or 

spring.

Selective herbicide used on noncrop sites; may cause temporary 

injury to some grass species.

Aminocyclopyrachlor

+ metsulfuron methyl

Streamline 4.75–9.5 ounces Same as above. Same as above. Same as above.

Aminopyralid Milestone 3–5 ounces 3–5% Rosette through 

bolting stage.

Labeled for use in natural areas 

such as wildlife management

areas. No grazing restrictions.

Picloram4 Tordon 22K 1–1.5 pints 1–3% Fall to early spring,

at early rosette

stage.

Selective broadleaf herbicide; 

may pose a risk to groundwater 

in permeable soils or in areas

where the water table is near the

surface.

Picloram4 + 2,4-D3 Grazon P+D 2 quarts (1:4 

mixture)

1–3% Same as above. Same as above.

Metsulfuron methyl Escort XP 1 ounce NA Same as above. Selective broadleaf herbicide.

Most perennial grasses are

tolerant; residual.

Metsulfuron methyl + 

2,4-D3 + dicamba

Cimarron Max Rate III (1 

ounce Part A + 

4 pints Part B)

NA Same as above. Same as above.

Dicamba + 

diflufenzopyr

Overdrive 4 ounces 1–3% Same as above. Selective broadleaf herbicide; 

not for use where surface water

is present.

Triclopyr Remedy 3 pints 1–1.5% Best on seedlings to

early rosette stage.

Selective broadleaf herbicide; 

little residual.

2,4-D3 several

manufacturers

1 quart 5–10% Rosette to early bud 

in the spring.

Non-persistent; growth 

regulator; may be less effective

alone.
7 

Table 3. Herbicide recommendations (cont.)

Common

Chemical Name

(active ingredient)

Product

Example(s)1

Broadcast 

Treatment 

(rate per acre)

Spot Treatment 

(spray solution)2

Time of

Application Remarks

Imazapyr Arsenal 1 pint 1% All stages. Nonselective herbicide. In 

addition to spray drift, nontarget

plants may also be killed or 

injured by imazapyr through 

runoff, residue movement in 

soil, or root exudates from 

treated plants. Use only in areas 

where total plant control is 

desired such as roadsides.

Glyphosate Rodeo

Round Up

Rodeo: 4.5–7.5 

pints

Round Up: 1.5–

4 quarts

Rodeo: 0.75–2%

Round Up: 1–2%

One week before

reseeding.

Nonselective herbicide. Use only 

for site preparation in a reseeding

program. 

1 Trade names for products are provided for example purposes only, and other products with the same active ingredient(s) may be available. Individual product 

labels should be examined for specific information and appropriate use with yellow starthistle.

2 Spray solution is the herbicide/water ratio in a spray mix that may be used for spot treatment with backpack or hand-held sprayers. The amount of product 

applied during an annual growing season must not exceed the maximum application rate per acre as specified by the product label – refer to the product 

label for the site type and application.

3 2,4-D is a restricted use pesticide in New Mexico only. A certified applicator’s license is required for purchase and use.

4 Restricted use pesticide - A certified applicator’s license is required for purchase and use.

Integrated Control Methods

Using a combination of control methods will improve 

treatment effectiveness for yellow starthistle. The 

following treatment combinations may be used to manage 

infestations:

• Herbicide–burn – As an initial treatment, use 

herbicide in a broadcast spray for seedlings and 

young plants in the rosette stage during fall or early 

spring. The treatment will eliminate the majority of 

the yellow starthistle population and allow grasses to 

become established. The herbicide treatment can 

then be followed the next year (or possibly in 2 

years) with prescribed fire, which may require 

authorization from local air quality authorities. 

Burning is best performed when non-target grasses 

have dried but before yellow starthistle produces 

seed which is likely to occur during late May or June 

in New Mexico and Arizona. This treatment 

combination can benefit the range plant community

by increasing species diversity and enhancing the 

quality and quantity of forage. Consider introducing 

biocontrol agents after the last burn.

• Herbicide–reseed–graze – While experience in 

New Mexico and Arizona islimited, a herbicide–

reseed–graze treatment sequence has been used in

California with some success. In this approach, a 

broadcast application of glyphosate is made to the 

infested site in late winter. The area is then reseeded 

one week later with a variety of appropriate 

perennial grasses by using a no-till drill. Two weeks 

after seeding, a broadcast application of clopyralid 

is made to control pre-emergent and post-emergent 

yellow starthistle plants. Light fall grazing is

recommended for several years after planting until 

perennial plants are well established. Treated areas 

should be closely monitored to determine if further 

herbicide application is necessary.
8

Management Strategies

Strategies to contain, reduce, or eradicate yellow starthistle 

require long-term planning, integrated management, and 

follow-up monitoring. Due to yellow starthistle’s prolific

seed production, initial treatment should attempt to

eliminate live plants and disrupt flower production as 

much as possible. A high priority should be treatment of 

small or sporadic infestations on otherwise healthy sites, 

which can then be shifted to larger infestations.

Regardless of the strategy employed, the key to successful 

yellow starthistle control is persistent, long-term 

management. In many cases, 3 or more years of intensive 

management may be necessary to reduce a starthistle 

infestation significantly. Since it is ordinarily useless to 

treat an area only one time without retreatment, sufficient 

resources must be allocated for the area where control is 

attempted. After initial treatment, it is especially important 

that resources are also available to respray or retreat 

treated areas as necessary. Treated areas should be 

monitored, and secondary treatment made to control newly 

emerged or missed plants. Always encourage growth of 

perennial grasses and other desirable plant species that will 

compete with yellow starthistle for soil moisture, light, 

nutrients, and space.

References and Further

Information

Davison, J.C., E. Smith, and L.M. Wilson. 2007. Livestock 

Grazing Guidelines for Controlling Noxious Weeds

in the Western United States. Available at

http://www.cnr.uidaho.edu/rx-grazing/Livestock 

_Grazing_Guidelines%28Davison_et_al. 

%202007%29.pdf (accessed June 2010).

DiTomaso, J.M. Undated. Yellow Starthistle. UC Weed

Research Information Center Web site. Available at 

http://wric.ucdavis.edu/yst/yst.html (accessed 18

June 2010).

DiTomaso, J.M. 2001. Element Stewardship Abstractfor 

Centaurea solstitialis L. Available at http://www. 

invasive.org/weedcd/pdfs/tncweeds/centsol.pdf 

(accessed 17 June 2010).

DiTomaso, J.M. and E.A. Healy. 2007. Weeds of

California and Other Western States. University of

California Agriculture and Natural Resource 

Publication 3488. Pp. 250–260. Available at

http://books.google.com/books (accessed 17 June

2010).

Duncan, K., K. McDaniel, and M. Renz. 2005. Chemical

Weed and Brush Control for New Mexico 

Rangelands. New Mexico State University

Cooperative Extension Service. Las Cruces, NM. 

pp. 12. Available athttp://aces.nmsu.edu/pubs/ 

_circulars/CR_597.pdf (accessed 17 June 2010).

Encycloweedia Datasheets by California Department of 

Food and Agriculture. Available at

http://www.cdfa.ca.gov/phpps/IPC/weedinfo/ 

centaurea2.htm (accessed 17 June 2010).

Enloe, S.F., J.M. DiTomaso, S.B. Orloff, and D.J. Drake. 

2005. Perennial Grass Establishment Integrated 

with Clopyralid Treatment for YellowStarthistle

Management on Annual Range. WeedTechnology 

19:94-101.

Gerlach, J.D., Jr. and J.M. DiTomaso. 2000. Yellow 

Starthistle (Centaurea solstitialis). In C. C. Bossard 

et al. (eds.) Invasive Plants of California’s 

Wildlands University of California Press. Berkley, 

CA. Available at http://www.cal-ipc.org/ip/

management/ipcw/online.php (accessed 17 June 

2010).

Great Basin and Invasive Weeds: Yellow Starthistle 

(Centaurea solstitialis) fact sheet. Available at 

http://www.usu.edu/weeds/plant_species/ 

weedspecies/ystarthis.html (accessed 17 June 

2010).

Lym, R.G. 2002. Yellow Starthistle Identification and 

Control (Stop the Spread Factsheet). North Dakota 

State Univ. Extension Service Publication W-1222. 

Available at http://www.ag.ndsu.edu/pubs/plantsci/ 

weeds/w1222w.htm (accessed 17 June 2010).
9

Murphy, A. 2005. Least Wanted: Yellow Starthistle Fact 

Sheet. Plant Conservation Alliance. Available at 

http://www.nps.gov/plants/alien/fact/ceso1.htm 

(accessed 17 June 2010)

Turner, J.L., K. Duncan, and J. LeFevre. 2011. Russian 

knapweed and yellow starthistle poisoning of 

horses. Guide B-170. Cooperative Extension Serv., 

College of Agriculture, Consumer, and 

Environmental Sciences. New Mexico State Univ. 

Las Cruces, NM. Available at http://aces.nmsu.edu/ 

pubs/_b/b-710.pdf.

Whitson, T.D., et al. (ed.). 2000. Weeds of the West. 

Western Society of Weed Science in cooperation 

with Cooperative Extension Services. University of 

Wyoming, Laramie. Available at 

http://plants.usda.gov/java/invasiveOne?pubID=W

SWS (accessed 17 June 2010)

Wilson, L.M., C. Jette, J. Connett, and J.P. McCaffrey. 

2003. Biology and Biological Control of Yellow 

Starthistle. 2nd ed. USDA Forest Service FHTET1998-17. Available at http://www.cnr.uidaho.edu/

crissp/CRISSP%20pdf/StarthistleBook.pdf 

(accessed 17 June 2010). 

Zouhar, Kris. 2002. Centaurea solstitialis. In Fire Effects 

Information System. USDA, Forest Service, Rocky 

Mountain Research Station, Fire Sciences 

Laboratory (Producer). Available at 

http://www.fs.fed.us/database/feis/plants/forb/ 

censol/all.html (accessed 17 June 2010).

Suggested Web Sites

Invasive Plant Atlas of the United States. Available at: 

http://www.invasive.org/weedus/index.html.

For information about calibrating spray equipment: NMSU 

Cooperative Extension Service Guide A-613,

Sprayer Calibration. Available at 

http://aces.nmsu.edu/pubs/_a/A-613.pdf

Herbicide labels online:

http://www.cdms.net/

USDA Plants Database. 2010. Available at: 

http://plants.usda.gov/index.html.
For more information or

other field guides, contact:

USDA Forest Service 

Southwestern Region

Forest Health

333 Broadway Blvd., SE 

Albuquerque, NM 87102

Or visit the Southwestern Region’s 

website for invasive species:

http://www.fs.usda.gov/goto/r3/invasivespecies

The use of trade or firm names in this publication is for reader 

information only and does not imply endorsement of any 

product or service by the U.S. Department of Agriculture. 

Recommendations made here for 

pesticide use are not obligatory, 

nor do they imply that discussed 

uses have been registered. All 

uses of pesticides must be 

registered by appropriate State 

and/or Federal agencies before 

they can be applied. 

CAUTION: Pesticides can be 

injurious to humans, domestic 

animals, desirable plants, and fish or other wildlife—if they are 

not handled or applied properly. Use all pesticides carefully 

and lawfully. Follow recommended practices for the disposal 

of surplus pesticides and pesticide containers.