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Centaurea solstitialis
Yellow Starthistle
Scientific classification
Kingdom:	Plantae
(unranked):	Angiosperms
(unranked):	Eudicots
(unranked):	Asterids
Order:	Asterales
Family:	Asteraceae
Tribe:	Cynareae
Genus:	Centaurea
Species:	C. solstitialis
Binomial name
Centaurea solstitialis L.

Yellow Starthistle (Centaurea solstitialis) is a member of the Asteraceae family, native to the Mediterranean region. The plant, also known as Golden Starthistle, Yellow Cockspur and St. Barnaby's Thistle (or Barnaby Thistle)^[1] is a thorny winter annual in the knapweed genus.

It is a grayish-green plant with multiple rigid stems that extend in all directions from the base, forming a bushy-looking cluster that can reach two meters in height and more than that in diameter. It produces bright yellow flowers ringed with long, sharp spines. The plant grows quickly and is very competitive. It bears a taproot that can reach a meter deep into the soil, allowing it to thrive during dry, hot summers. It is versatile in its growth patterns, and can adapt to drought or low soil moisture content by producing smaller plants with fewer seeds during dry years.

Since its introduction to California in the mid-nineteenth century,^[2] it has become a large-scale noxious weed throughout the United States, currently dominating over 15,000,000 acres (61,000 km²) in California alone.^[3]

Similar Species

Red Star thistle Centaurea calcitrapa (see article for further description), and Rough Star-thistle Centaurea aspera. ^[4]

Invasive Species

The plant grows as a normal part of the ecology in Eurasia, where it is kept in check by an assortment of natural enemies and other plants that have co-evolved with it in its native habitat. (see co-evolution)

Its introduction in North America probably occurred in California sometime after the start of the California Gold Rush, as a seed contaminant in Chilean-grown alfalfa seed, also known as Chilean clover (Trifolium macraei).^[2] After the turn of the century, Spain, France, Italy, and perhaps Turkestan were also likely sources of invasion.^[2]

It was dispersed into agricultural fields in California, and immediately took hold in the area's Mediterranean-type climate. Human factors such as mowing, domestic animal grazing, and cultivation of wildlands contributed to the success and spread of the plant. It is now a very common sight in pastures, fields, and vacant lots, and along roadsides.

By 1970,^[5] yellow starthistle had reached 23 states.^[2] According to the USDA Forest Service,^[6] as of 2006 the plant has been reported present in 41 of the 48 contiguous U.S. states, with the only exceptions being Maine, Vermont, and five of the Deep South states (Arkansas, Louisiana, Mississippi, Alabama, and Georgia). The plant is considered an invasive species in six of the 41 states: California, Oregon, Washington, Idaho, Utah, and New Jersey.

The yellow starthistle plant has the ability to create monotypic stands in fields that prevent other species from growing there. Whole fields of solid yellow starthistle are not uncommon. Its growth plasticity, competitiveness, preference for the Mediterranean climate, and lack of natural enemies and co-evolved species make it a very successful invader. The plant is a pest in field crops, prevents domestic animals' grazing in rangelands, and acts as a physical barrier to wild animal movement in wildlands. It is toxic to horses.^[7]

Chemical Control

Most herbicides used for controlling yellow starthistle are registered for rangelands, right-of-way and other non-crop areas. Many auxin-like or growth-regulator herbicides are used for post-emergence control, including 2,4-D, aminopyralid, clopyralid, dicamba, picloram and triclopyr. Alternatively, glyphosate may be used. Pre-emergence herbicides used for yellow starthistle control include chlorsulfuron and sulfometuron. Pre-emergence and post-emergence herbicides may be used effectively together to kill growing plants as well as any new seedlings that may emerge from the copious soil seed bank often produced by yellow starthistle. Controlled burning may also be used in conjunction with clopyralid application as an effective integrated approach to yellow starthistle management.^[8]

A yellow starthistle biotype resistant to picloram was discovered in a pasture near Dayton Ohio in 1988. This biotype was determined to have cross resistance to other auxin-like herbicides, especially clopyralid ^[9] Resistance was discovered to be conveyed by a single nuclear recessive gene. ^[10]

Biological Control

C. solstitialis in California, autumn 2007.

Yellow starthistle is sometimes resistant to removal methods such as mowing and burning, because of its long root system and the seeds' ability to withstand fire. The plant has been the target of biological pest control programs with positive results. Seven types of seed-feeding insect have been released (one accidentally) to control the plant.^[11] (Pitcairn 2008)

• Three species of weevil in the beetle subfamily Cleoninae effectively reduce seed production in the yellow starthistle.
  • Yellow starthistle bud weevil (Bangasternus orientalis) is a fuzzy brown weevil that lays its eggs in the flowers, and when its larvae hatch, they feed on the developing seed. ^[12]
  • Yellow starthistle hairy weevil (Eustenopus villosus) is a long-snouted, hairy-looking weevil that lays a single egg inside each flower bud. The larva then consumes the seeds within.^[13][14]
  • Yellow starthistle flower weevil (Larinus curtus) is a brownish weevil that lays eggs in the flowers as it feeds on the pollen. The larvae then eat the seeds when they hatch.^[15] This insect has failed to established dense populations in the United States (Pitcairn 2004, Pitcairn 2005).
• Four species of tephritid fruit fly also attack the seedheads of yellow starthistle.
  • Yellow starthistle peacock fly and false peacock fly (Chaetorellia australis and Chaetorellia succinea, respectively, the latter released unintentionally) are small nectar-feeding flies that deposit eggs into the seedheads, where their larvae consume the seeds and flower ovaries.^[16]
  • Banded yellow starthistle gall fly (Urophora sirunaseva) produces larvae that pupate within a woody gall within the flower and disrupt seed production.^[17]
  • Another gall fly Urophora jaculata was released in 1969 but never established.

Additionally, a variety of the rust fungus Puccinia jaceae var. solstitialis, first released in July 2003 on a ranch in the Napa Valley, has shown promise as an agent against yellow starthistle.^[18] The rust causes widespread pathology in the leaves of the plant and slow its dispersal.

Although these biocontrol agents have proven somewhat effective at controlling starthistle, there is interest in finding additional agents to further control the species. Two weevils, including Larinus filiformis, and a flowerhead feeding weevil, and Ceratapion basicorne (Illiger) (Coleoptera: Apionidae), which develops in the root crown of rosettes have been evaluated and proposed for introduction (Smith 2007). Also under evaluation are a stem-feeding flea beetle Psylliodes chalcomera (Illiger) (Coleoptera: Chrysomelidae) (Cristofaro et al. 2004a), a lacebug Tingis grisea Germar (Heteroptera: Tingidae), and a mite Aceria solstitialis de Lillo (Acari: Eriophyidae) (de Lillo et al. 2003) (Smith 2004).

References

• http://search.nal.usda.gov/bitstream/10113/21568/1/IND44130286.pdf
• Balciunas, J. K., and B. Villegas. 2001. Unintentionally released Chaetorellia succinea (Diptera: Tephritidae): Is this natural enemy of yellow starthistle a threat to safflower growers? Environ. Entomol 30: 953-963.
• Pitcairn, M. J., G. L. Piper, and E. M. Coombs. 2004. Yellow starthistle, pp. 421Ð435. In E. M. Coombs, J. K. Clark, G. L. Piper, and A. F. Cofrancesco, Jr. (eds.), Biological control of invasive plants in the United States. Oregon State University Press, Corvallis, OR.
• Pitcairn, M. J., D. M. Woods, and V. Popescu. 2005. Update on the long-term monitoring of the combined impact of biological control insects on yellow starthistle, pp. 27-30. In D. M. Woods (ed.), Biological control program annual summary, 2004. California Department of Food and Agriculture, Plant Health and Pest Prevention Services, Sacramento, CA.
• Pitcairn, M. J., B.Villegas, D. M. Woods, R. Yacoub, and D. B. Joley. 2008. Evaluating implementation success for seven seed head insects on Centaurea solstitialis in California, USA, pp. 610-616. In M. H. Julien, R. Sforza, M. C. Bon, H. C. Evans, P. E. Hatcher, H. L. Hinz, and B. G. Rector (eds.), Proceedings of the XII International Symposium on Biological Control of Weeds. La Grande Motte, Montpellier, France (in press).
• Smith, L. 2004. Prospective new agents for biological control of yellow starthistle, pp. 136-138. Proceedings 56th Annual California Weed Science Society, 12-14 January 2004, Sacramento, CA.
• Smith, L. 2007. Physiological host range of Ceratapion basicorne, a prospective biological control agent of Centaurea solstitialis (Asteraceae). Biol. Control 41: 120-133.

External links

• Images from the CalPhotos archive from a University of California, Berkeley website
• http://www.cal-ipc.org/symposia/archive/pdf/2007/4.1biocontrol-smith.pdf

From Wikispecies

Centaurea solstitialis

Taxonavigation

Classification System: APG II (down to family level)

Main Page
Cladus: Eukaryota
Regnum: Plantae
Cladus: Angiospermae
Cladus: Eudicots
Cladus: core eudicots
Cladus: Asterids
Cladus: Euasterids II
Ordo: Asterales
Familia: Asteraceae
Subfamilia: Cichorioideae
Tribus: Cardueae
Subtribus: Centaureinae
Genus: Centaurea
Species: C. solstitialis

Name

Centaurea solstitialis L.

References

• Species Plantarum 2:917. 1753
• USDA, ARS, National Genetic Resources Program. Germplasm Resources Information Network - (GRIN) [Data from 07-Oct-06]. [1]

Vernacular names

For more multimedia, look at Centaurea solstitialis on Wikimedia Commons.