Diffuse knapweed is difficult to distinguish from spotted knapweed without looking at the bracts. This species infests only 20 acres in North Dakota, but has the potential to spread significantly. There is great potential for spread of knapweeds. In Montana and Minnesota, knapweeds infect more acres than leafy spurge. At least one of the three species has been found in 25 counties in North Dakota.
People are the major cause of knapweed spread.
Producers should exercise caution when using hay from road ditches or purchasing hay from infested areas and land managers need to learn how to identify and control these plants. Timely control now will be very cost effective compared to treating larger acreage later. For more information on the knapweeds or purple loosestrife, contact your local office of the NDSU Extension Service.