Editing Centaurea diffusa (section)

===Effects===
By 1998 diffuse knapweed had naturalized over {{convert|26640|km2|sqmi}} in the western US, and was increasing its range at a rate of 18% annually. Diffuse knapweed can establish itself in grassland, scrubland and riparian environments. It has little value as feed for [[livestock]], as its thistles can damage the mouth and digestive tract of animals that attempt to feed on it. A study in 1973 concluded that ranches lost approximately [[United States dollar|US$]]20/km<sup>2</sup> (8 cents per acre) of diffuse knapweed due to decreased grazing area. In an agricultural setting, it can greatly reduce crop yield and purity. {{Citation needed|date=July 2007}}