Spotted Knapweedand
Diffuse Knapweed
Centaurea maculosaand
Centaurea diffusa
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.