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



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