The largest impact of humans on diffuse knapweed is certainly due to our efforts in controlling and eradicating its invasive populations. The several methods outlined in the control section represent a small sample of literally hundreds of approaches being tried with varying levels of effectiveness. Besides reducing the spread of diffuse knapweed, we are also providing selective pressure against the individuals that cannot withstand a certain method of control. Selective pressure, given sufficient time, can cause the adaptation or evolution of invasive species such as diffuse knapweed. If an individual diffuse knapweed plant survives control efforts because of a trait it possesses, its progeny will make up a greater portion of the population than the plants that succumbed to the control.