Russian knapweed

Native to Mongolia, western Turkestan, Iran, Turkish Armenia, and Asia Minor, Russian knapweed is a highly competitive knapweed variety. Russian knapweed was first introduced to Canada around 1900 as a contaminant of Alfalfa seed. It is currently found in the largest concentrations in the Keremeos area, and in smaller patches in the east Kootenay region, Okanagan, Merritt, Kamloops and William’s Lake areas. Russian Knapweed thrives in any soil, but does very well in clay soil. Russian knapweed prefers open areas and well-drained soils and can become established in grasslands, open forests, and along roadsides and right-of-ways. However, it is intolerant of shade, prolonged drought, and wet sites.  

• Knapweed plants are highly competitive, forming dense colonies in disturbed or overgrazed lands.  
• Once established, knapweed can dominate an area and significantly reduce desirable vegetation.  
• Russian knapweed is particularly a threat to the stability of ranching operations. Russian knapweed can reduce available forage and crop values and may even significantly devalue the land itself.  
• Other losses include soil erosion and reductions in wildlife populations due to the decrease in forage production.  
• Grazing animals generally avoid knapweed due to its bitter taste; however, under poor-range conditions animals will graze knapweed.  
• Russian knapweed is toxic to horses and can cause the neurological disorder, chewing disease. This disease is limited to horses and does not occur in cattle, sheep or goats.  

The most effective way to ensure that your lands do not become infested with Russian knapweed is by prevention. Here are some recommendations to prevent invasion on your property: 

• Maintain grasslands in a healthy, vigorous condition to ensure a productive plant community; competitive perennial grasses and forbs utilize water, nutrients and space that would otherwise be readily available to knapweed.  
• Regularly patrol your property for knapweed plants and immediately treat new infestations before seed set. Do not leave plants to compost as they may still produce viable seed.
• Cooperate with adjacent landowners and encourage them to control knapweed and other weeds.  
• Immediately revegetate disturbed, bare soils with a suitable seed mix that provides dense, early colonization to prevent weed invasion.  
• Clean your vehicles and machinery of plant material and soil before leaving a knapweed infestation.  
• Check seed for contaminants and use only certified seed.  
• Learn to identify the different species of knapweed and other noxious weeds.  
• Do not move contaminated soils to a new area. 

• A combination of cutting and herbicides can be used to manage Russian knapweed. 
• Cutting or mowing will reduce the current year growth and may eliminate seed production, but will not kill Russian knapweed. Plants should be mowed or cut aggressively several times before plants bolt to weaken the root reserves. Wherever possible, the root system should be removed to prevent re-sprouting. 
• If plants have not yet flowered, the removed plants can be left onsite, but stems should be twisted, bent, or otherwise crimped.  
• If treatment is performed while flowers are present on stems, the plants must be bagged and removed from the site, and taken to a landfill. 
• Areas free of Russian knapweed should be monitored annually and all plants found should be destroyed immediately. 
• Before applying herbicides, read the label for full use and precautionary instructions. For further information on the selection and application of chemicals to protect your crop, contact AgriService BC at 1-888-221-7141 or email AgriServiceBC@gov.bc.ca
• A nematode biological control agent, Scubanguina picridis, has been experimented with in B.C. and Colarado but is currently not available for general distribution. Biological control agents that attack diffuse and spotted knapweed will not transfer to Russian knapweed. 
• Fire is not an effective agent against this plant.