How can you kill knapweed?

A treatment schedule with 2,4-D is a way of killing knapweed. The application must be made in October and November for the best chance of success. Even under the best of treatment schedules, it will be difficult to control the Centaurea genus member in question even though any two of controlled burn, extreme cutting and pesticide schedules tend to eliminate any non-woody or woody plant within one to three years.