Introduction
 Spotted and diffuse knapweed are biennials and sometimes perennials.  They were most likely introduced through contaminated alfalfa seed from Asia minor.  They may also have been introduced through soil used as ballast for ships.

Environmental Impacts
 Spotted and diffuse knapweed will take over rangeland quickly.  They, like many other noxious weeds, become easily established in disturbed areas.  Once established they will continue to spread to undisturbed areas.  Spotted and diffuse knapweed are largely unpalatable to livestock.  They have chemicals that are undesirable to livestock.  Spotted and diffuse knapweed are both noxious weeds in Nebraska.

Remedial Action
 Since spotted and diffuse knapweed favor disturbed areas a good management strategy is to make sure the land is not being disturbed.  Overgrazing is a common means of disturbance for soil.  Proper grazing management will help prevent an infestation.  Once spotted and diffuse knapweed have become established perhaps the only way to control the problem is to use chemicals and then try to establish native vegetation in place of the stand of knapweed.