INVASIVE PLANT
YELLOW STARTHISTLE
Presented by
Bignon Elsa
NRES 641
Introduction
Outline
1-General characteristics
 2- Biology and
characteristics that makes
Yellow starthistle a good
invader
 3- Impacts
 4- Management
 5- Conclusion


1- General characteristics
 A B-
 C-
Taxonomy
Identification, description
Origin and habitat:
1-General characteristics
A- Taxonomy



Group: Dicotyledonous
Order: Asterales
Family: Asteraceae
Genus: Centaurea
Species: Centaurea solstitialis L.
SYNONYMS Yellow starthistle (YST) :
Golden starthistle, yellow cockspur, St. Barnaby's
thistle, Cottontip thistle.
1-General characteristics
B- Identification, description
Yellow starthistle (YST) ( DiTomaso,
2007):






Gray-green to blue-green plant
Deep and vigorous taproot.
Yellow flowers with spines
adjoining the base.
heights varying from 6 inches to 5
feet
rigid stems covered with a cottony
wool
Basal leaves are 2 to 3 inches long
and deeply lobed.
1-General
characteristics
1-General characteristics
COrigin
and
habitat:
C- Origin and habitat:




Origin of yellow starthistle: Eurasia. It is
native to Balkan-Asia Minor, the Middle
East and south-central Europe
(Maddox, 1981).
introduction into USA (1849) via South
America as a seed contamination in
alfalfa seed (Gerlach et al. 1998 ).
Now YST is found in 41 states and in 5
western national parks - Death Valley
National Park, Glen Canyon National
Recreation Area, Redwood National
Park, Sequoia and Kings Canyon
National Parks, and Yosemite National
Park. (Murphy, 2005)
In California, the plant infests between
10 and 15 million acres (DiTomaso,
2007) .
Absent
present
Distribution of Yellow starthistle.
Source:USDA website
1-General characteristics
C- Origin and habitat (cont.):

found typically in:
 full
sunlight
 Deep well-drained soils, (annual rainfall 10-60
inches)
 common in rangelands, pastures, hay fields,
orchards, vineyards, waterways, roadsides, and
even forests and other non-crop areas or in
disturbed areas such as roadsides. (Zimmerman et al., 2001)

2- Biology and characteristics that make
Yellow starthistle a good invader
 A-
Seed production and germination
 B-Growth
 C-Reproduction and flowering
2- Biology and characteristics that makes Yellow
starthistle a good invader
A- Seed production and germination


Winter annual plant,
germinates in early
spring
Only can reproduce by
seed  prolific seed
producer 35 to over 80
achenes per seedhead .
(Benefield et al. 2001, Maddox 1981).

A plant can produce up
to 150,000 seeds
(Zimmerman et al., 2001)
Phenological development of
yellow starthistle flowers from
pre-bloom spiny stage to petal
abscission.
Seed viability occurred at late
senescence stage.
Source: DiTomaso 1996
Time period from
flower initiation to the
development of mature
viable seed is only 8
days. (DiTomaso, 2006 )
2- Biology and characteristics that makes Yellow
starthistle a good invader
A- Seed production and germination (Cont.)

Two types of seed inYST
seedheads (DiTomaso, 1996) :
 Dark
and lack a pappus.
 Majority:
brown with a
bristly pappus ring at
the apex
yellow starthistle seeds
Source: www.cdfa.ca.gov/centaurea-solstitialis.htm
2- Biology and characteristics that makes Yellow
starthistle a good invader
A- Seed production and germination (Cont.)

Good light + good soil
moisture + good
temperature (50 °F to 70 °F)
= nearly 100% seeds can
germinate (DiTomasso et al,
2006)



90% of YST achenes are
germinable 1 week after
seed dispersal (Benefield et
al. 2001).
YST achenes depleted by
80% after 1 year
By 3 years only 3.9% still
viable (Joley et al. 1992)
Decline in seedbank. When the introduction
of new seeds is prevented, the yellow
starthistle seedbank declines almost
completely over three years.
Source: Joley et al. 1992 Dynamics of yellow starthistle
(Centaurea solstitialis) achenes in field and laboratory

2- Biology and characteristics that makes Yellow starthistle a good
invader
B- Growth



After germination, YST will dedicate
most of its energy to root growth,
leaf expansion, stem development
and flowers (Roche et al 1994).
Roots can extend more than 3 feet
into the underground.
Rapid germination + deep root
growth are traits that allow it to
compete very well against shallowrooted native plants during the hot
and dry summer months. (DiTomasso ,
24 days
after
planting
31 days
1996)
38 days
44 days
Root growth. Roots of yellow starthistle plants
grow deep rapidly, even in the rosette stage.
Source: DiTomasso et al. 2006
52 days
2- Biology and characteristics that makes Yellow starthistle a good
invader
C- Reproduction and flowering



YST begins flowering in late May and
continues through September
It has very low levels of self-fertilization
(Harrod and Taylor 1995, Maddox et al.
1996). a large amount of crossfertilization insures a high degree of
genetic variability within populations (
Dittomaso et al 2006).
Importance of Honeybees:
 Honeybees maintain high
pollination rates.
 Contribution may be >50% of the
seed set. ( Barthel et al. 2001) .

 honey bees and yellow starthistle may
act as invasive mutualists.
A honey bee foraging at a flower head
of yellow star-thistle.
Source: Haag.E, February 2009

3-Impacts
 A-
Negative impacts
 Economic
 Toxicity to
horse/ dangerous for livestock
 Roadside and recreational area
 Wildland
 Water consumption

B-Positive impacts
 Honey
 Food for ruminants
3- Impacts
A- Negative impacts
Economic
Economic



In California 0.5 million acres are
managed at about $25 per acre for a
cost of about $12.5 million annually in
management (DiTomaso et al. 2006).
YST : significant issue and
considered one of the most
serious rangeland, grassland,
and wildland weeds in the
western of the United States.
Infest grain harvested 
decrease crop quality + value.
Significant direct costs to control
YST on public lands (e.g costs of
materials
 labor for treatments

3- Impacts
A- Negative impacts
 Toxicity to horse/ Dangerous for livestock

Horses eat YST: Chronic poison
which causes neurological disorder
of the brain: nigropallidal
encephalomalacia or “chewing
disease.”




No treatments known
Most of the time the animal dies
LD : 2.3 to 2.6 kg YST/ 100 kg of
body weight per day (Cheeke and Shull ,1985).
Only horses are affected by YST.
YST sharp spines
Source/ az.gov/invasivespecies/tenmostunwanted.html
All grazing animals can have eye
damages due to the plant’s long,
sharp spines (Haag, 2009)
3- Impacts
A- Negative impacts
 Roadside and recreational area


YST is the most important roadside weed problem in
much of central and northern California . (Maddox et al.1985),
Spread along roadside with contaminated soil,
vehicles and equipments (DiTomaso et al 2006)
2- Impacts
A- Negative impacts
 Roadside and recreational area (cont)


YST can limit or impede human access if the area is
infested. (trails and campgrounds, hunting areas,
and recreational vehicle parks)
On certain military bases, YST can impact training
exercises and can impair the use of equipment (e.g.,
snagged parachutes, torn clothing)+ YST can cause
mechanical injury to humans (particularly to the
face) when the spines are encountered (Miller, 2003).
3- Impacts
A- Negative impacts
 Wildland


YST is directly responsible for transforming millions of acres of complex and
diverse native ecosystems into marginal plant communities most of time
dominated by a single species (Haag E, 2009, DiTomaso et al. 2006; Zimmerman et al., 2001).
YST affects fire frequency by changing fuel characteristics. This may impede the
reestablishment of native species because the community cannot find the initial
fire balance (DiTomaso et al.2006).
3- Impacts
A- Negative impacts
 Water consumption

YST affects soil moisture:



YST has caused losses of soil moisture resources on invaded sites of
15–25% of mean annual precipitation. (Gerlach, 2003)
Major consumer of groundwater, costs the state millions of dollars
in lost water for wildlife, agriculture and municipal uses.
Based on a conservative estimate of YST coverage in the
Sacramento River watershed: YST may cause an annual economic
loss of $16 to $75 million in water conservation costs alone. Gerlach,
(2003)

Because of its high water usage, YST threatens both human
economic interests as well as native plant ecosystems.
3- Impacts
A- Positif impacts
 Honeybee and livestock food


Yellows starthistle Honeybee.
Source: http://ecx.imagesamazon.com/images/I/41zWKE3SpzL._SL500_.jpg


The weed is regarded as an important honey
plant and late-season food source for bees in
California (Barthell et al. 2001).
YST has acceptable nutritional value as a
component of a ruminant’s diet and leaves are
highly digestible by ruminant during growing
season. (Thomsen et al. 1989).
And YST is available to cattle at a time when
most grasses and forbs are past and have poor
nutritional value. (Haag, 2009)
But


YST nutritional value declines as the plants grows.
Pasture infested contain considerably less crude
protein and total digestible nutrients compared
to uninfested pastures (Barry, 1995).

4- Management
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


A-Biopredation
B- Cultural Control
C- Chemical control
D-Integrated approach
4- Management
A- Biopredation


Biological control goal is to use natural enemies to control a target weed.Research
began in the mid 1960s and continues today. (DiTomaso et al. 2006)
Five insects (natural enemies from Europe) :




They directly or indirectly reduce seed production by attacking the flower/seed
head.
Advantages:



highly host-specific to the weed
do not attack commercially valuable crops or native plants.
Disadvantages:



three weevils (Bangasternus orientalis and Eustenopus villosus and larinus curtus)
and two flies (Urophora sirunaseva and Chaetorellia succinea).
only suppress about 50%, of YST seed production so,
they should not be considered as the exclusive method of control. ( DiTomaso et al. 2007)
Most recently the rust fungus Puccinia jaceae var. solstitialis was released in
California. It was the first pathogen approved for biological control. It completes its
entire life cycle on YST. But it has not yet demonstrated a strong record of
persistence and regeneration. (Woods et al. 2010)
4- Management
A- Biopredation (cont)
Chaetorellia succinea
Source:
californiaagriculture.ucanr.org/landingpage.
Table 1 Comparaison of adult yellow starthistle weevils
Source: www.invasive.org/weeds/starthistle/chapter2.html
4-Management
B- Cultural control

Mowing



Grazing



Mowing early growth stages may results in increased light penetration and rapid
regrowth of the weed.
Repeated mowing of plants too early in their life cycles (rosette or bolting stages)
or when branches are below the mowing height will not prevent seed production,
as flowers will develop below the mower cutting height.
Sheep, goats, or cattle eat YST before spines form on the plant.
The plant’s crude protein concentration is variable but can be sufficient to meet the
general maintenance requirements for most ruminants. ( DiTomaso et al. 2007)
Burning
good way to reduce yst if it is applied when flowers appear.
 Burning for two or more consecutive years can help deplete the soil seedbank.
Burning is also a good way to increase the recovery and density of perennial
grasses. (DiTomaso et al. 2006)
 These practices are capable of reducing YST populations, but without competition,
it will often reestablish.

4-Management
B- Cultural control (cont.)

Revegetation

Species choice is dependant of the intended use site.
(e.g: resident vegetation such as perennial
bunchgrasses or wildflowers may be advantageous
along roadsides, abandoned pastures).

other methods (cultural, biological and chemical
control) can be used simultaneously to reduce YST
while encouraging other plant species.

In all instances, choose desirable species that
are well adapted to the site and not likely to
become invasive themselves. Species that grow
well are the best competitors. ( DiTomaso et al. 2007)
4- Management
C-Chemical control
Postemergent herbicides

Aminopyralid and clopyralid : growth regulator herbicides .Use in
noncrop areas. (They are postemergent and preemergent)

2,4-D (growth regulator)
 acceptable control of YST if applied in the rosette growth stage.

Dicamba (growth regulator)
 control YST at low rates in rosette stage(0.25 lb active
ingredient/acre).
 higher rates (0.5 to 0.75 lb active ingredient/acre) are needed if
plants are larger. ( DiTomaso et al. 2007)
4- Management
C-Chemical control
Postemergent herbicides (cont)

Triclopyr (growth regulator)
 is
effective at controlling seedlings
 but is not as effective on larger plants. More mature plants
require higher concentration of active ingredient. It is foliarabsorbed and active on broadleaf species, but typically does
not harm grasses. (DiTomaso et al. 2007)

Glyphosate (amino acid inhibitor).
 It
provides effective control of yellow starthistle at 1 lb active
ingredient/acre.
 But non selective and controls most plants, including grasses.
( DiTomaso et al. 2007)
4- Management
C-Chemical control
Preemergent herbicides


Preemergent Herbicides
Chlorsulfuron and sulfometuron :registered for roadsides and other
noncrop uses. Very effective when applied at 1 to 2 oz active
ingredient/acre. ( DiTomaso et al. 2007).
4-Management
D-Integrated approach


Combinations of prescribed burning + clopyralid =
very efficient.
But: When using this method it is important that:


prescribed burn be conducted the first year (or
possibly for 2 years) and then clopyralid be applied in
the last year of the program.
Then, a control of YST after the last year of
treatment can be accomplished by mowing, spot
spraying, or hand-pulling. ( DiTomaso et al. 2007).
Conclusion




YST is an important invader in the West of the United States,
particularly in California and in some parts of Nevada.
This successful invasion results from a
 good adaptation to a favorable climate and
 Biological characteristics that make it a good competitor
 a lack of enemies in the land it invades.
The most important impact is certainly the water
consumption which costs the state millions of dollars in lost
water for wildlife, agriculture and municipal uses each year.
Many ways to control it, included both effective chemical
methods and more biological methods (cultural control and
biopredation). Both methods are effectives, but an integrated
approach can be more efficient if it is well realized.
References :

Barthell, J.F., J.M. Randall, R.W. Thorp, and A.M. Wenner. 2001. Promotion of seed set in yellow star-thistle by honey bees: evidence of an
invasive mutualism. Ecological Applications 11(6):1870–1883.

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Pitcairn M. J. 2006. Yellow Starthistle Management Guide. Published by the California invasive Plant Council.

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
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
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
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
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
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
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
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