Yellow Starthistle

Pest: Yellow Starthistle (Centaurea solstitialis)

Pest Type: Annual Broadleaf Weed

Major Identifying Features: Gray-green to blue-green with a deep taproot, bright yellow flower with sharp spines surrounding the base, grow 5-6 feet tall, stems and leaves are covered with a dense cottony wool

Life Cycle: Long-lived winter annual

Pest Rating: Noxious

Management Rating: Very difficult

Host/Season/Outbreak Information: Grows in open areas on roadsides, rangeland, wild lands, hay fields, pastures, and waste areas, 10-15 million acres are infested in California, grows up to 7000 feet elevation, needs a lot of light, produces up to 30000 seeds per square meter, seeds germinate from fall through spring

Damage Information: Rapidly forms infestations and depletes soil moisture, prevents other species from growing, poisonous to horses, competitive with other plants

Management Options: Prevention by checking hay and livestock (both should not be shipped to uninvested areas if animals fed on starthistles), biological control with weevils, cultural control with a single cultivation after the rainy season, with mowing, grazing, burning, revegetation, chemical control with herbicides such as Aminopyralid, Dicamba, Triclopyr, Glyphosate, Chlorosulfuron (Warning On The Use Of Chemicals), integreated approaches

Sources:

http://www.ipm.ucdavis.edu

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