Spotted Knapweed

Centaurea maculosa

Family: Asteraceae

Description and Life Cycle

A short-lived perennial, spreading mainly by seed. Mature plants are 0.3-1.5 m tall, with long, fibrous tap roots. Stems are somewhat hairy when young and highly branched. The basal and lower stem leaves are pinnately lobed; the upper leaves have smooth margins. Young leaves have a fine coating of hairs. Flowers are 1-1.5 cm long, pink to purple; bracts of the flower head are black tipped, giving the head a spotted appearance. Flowering occurs from July through to September. Seeds are black or brown, 3mm long, and topped with bristles up to half the length of the seed. The plant contains volatile oils with a distinctive smell and an extremely bitter taste.

Biological Control Agents

• Agapeta zoegana - Moth
• Chaetorellia acrolophi - Fly
• Cyphocleonus achates - Beetle (weevil)
• Larinus minutus - Beetle (weevil)
• Larinus obtusus – Beetle (weevil)
• Metzneria paucipunctella - Moth
• Pelochrista medulana – Moth
• Pterolonche inspersa – Moth
• Puccinia jaceae – Fungi – Rust
• Sclerotinia sclerotiorum – Fungus (pathogen)
• Sphenoptera jugoslavica – Beetle
• Terellia virens – Fly
• Urophora affinis – Fly
• Urophora quadrifasciata – Fly
  

References

Cranston, R., D. Ralph and B. Wikeem. 2005. Field guide to noxious and other selected weeds of British Columbia. Gov. of BC. 94 p.

Powell, G. W., A. Sturko, B. Wikeem and P. Harris. 1994. Field guide to the biological control of weeds in British Columbia. B.C. Min. For. Res. Prog.