Invasive Watch: spotted knapweed

Spotted knapweed is an aggressive perennial forbthat invades rapidly and impedes the growth and development of native plant communities.

What to Look For

Spotted knapweed (Centaurea maculosa) is an invasive perennial that blooms from June to October. Distinguished by the black-tipped bracts that appear under its pink and light purple pedals, spotted knapweed commonly grows to 1 to 3 feet tall. The plant blooms from June to October and consists of multiple stems that hold up to 35 flower heads each. Each plant holds thousands of multicolored seeds.

Where Is Spotted Knapweed Found

Spotted knapweed is an aggressive forb that can be found in nearly every state in the United States. Known for infesting rangelands, this aggressive forb also gains prevalence along roads, trails and roadways as well as in pastures and other natural areas. Spreading by seed allows the spotted knapweed to disperse quickly through a number of sources, including vehicles, flowing water, wildlife, humans and livestock. It can also be carried as a contaminant in hay or crop seed.

How to Treat Spotted Knapweed

To prevent the inadvertent spread of spotted knapweed seeds, avoid traveling directly through areas in which the species is prevalent. Washing the undercarriage of vehicles that have been through weed-infested areas is also recommended. Once a plant community is established, temporary control can be provided by hand removal. While mowing will not control spotted knapweed, it may help in reducing seed production.

Supplementing mowing with the use of selective herbicides is recommended for improved control.

At only 2.85 ounces per acre, TerraVue herbicide is recommended for high-volume foliar applications before the weed flowers in the spring and early summer. Do not apply after the weed has flowered. Spot applications are also recommended for individual plants prior to infestation. 

Check treated sites regularly and re-treat if necessary. The prompt removal of new seedlings will also help limit the odds of infestation. TerraVue is a selective herbicide, meaning it will allow most native grasses to flourish while controlling spotted knapweed and many other troublesome broadleaf weeds. This selectivity offers an added measure of control against future infestations.

 

 

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™ ® Trademarks of Dow AgroSciences, DuPont or Pioneer, and their affiliated companies or their respective owners. When treating areas in and around roadside or utility rights-of-way that are or will be grazed, hayed or planted to forage, important label precautions apply regarding harvesting hay from treated sites, using manure from animals grazing on treated areas or rotating the treated area to sensitive crops. See the product label for details. TerraVue is not registered for sale or use in all states. Contact your state pesticide regulatory agency to determine if a product is registered for sale or use in your state. Always read and follow label directions.

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