Spotted knapweed (Centaurea maculosa)
 Native Substitutes:
 Control Methods  
Mechanical
 Chemical
 Biological
Mowing may help control; best to mow at peak flowering, and remove flowerheads from site or seed will develop from discarded flowers Effective means of control with selective herbicides, such as clopyralid, but caution in quality natural areas as it targets native forbs of the daisy and pea families as well

Thirteen insects identified
Early detection and pulling; wear gloves as can be irritating to some and scratches may fester     Two seedhead flies are most promising
Prescribed burning; only very hot burns are effective which may also damage native plants        
 
Appearance: Biennial or short-lived perennial forb, 2-3' high. Basal leaves form a rosette the first year from which grow 1-20 wiry, hoary, branched stems during the second year. Leaves: Alternate, grayish, hoary, and divided into lanceolate lobes, decreasing in size at the top. Flower: Thistle-like pink to purple flowers sit at the tips of terminal and axillary stems; bloom from July through September. Seed: Brownish, 1/4" long with small tuft of bristles; dispersal mostly stationary, over distance by rodents, livestock and commercial hay. Viable in the soil for 7 years. Root: Stout taproot.
Especially threatens dry prairie, oak and pine barrens, dunes and sandy ridges. Spotted knapweed is poisonous to other plants (phytotoxic). Spreads rapidly in artificial corridors, gravel pits, agricultural field margins and overgrazed pastures. A native of Europe and Asia it has become a serious problem in pastures and rangelands of the western states.
Wisconsin Manual of Control Recommendations for Ecologically Invasive Plants, 1997