Identification, Distribution, Impacts of Russian knapweed

1. Identification, Distribution, & Impacts of Russian knapweed Mark Renz, PhD Extension Weed Specialist NMSU

3. Russian Knapweed Identification: Lower Leaves are 2 to 4 inches long and deeply lobed. Upper leaves are smaller and less lobed with smooth margins. Flower heads occur on shoot tips, and are urn-shaped generally 1/4 to 1/2 inch in diameter with smooth papery bracts. Flower color can ranges from pink to lavender or white Roots are perennial, creeping, and have a distinct black scaly appearance.

6. Plant habit Stems erect 1-2 ft in height Lower Leaves lobed Upper leaves are smaller and less lobed with smooth margins

7. Impacts Extremely competitive plant As infestations develop they displace nearly all herbaceous resident vegetation Reduces forage for livestock Can nearly eliminate plant biodiversity Produce allelopathic chemicals that inhibit growth of other plants Compounds can hamper revegetation efforts Poisonous to horses Causes �chewing disease�, a neurological disorder that produces brain lesion and ulcers in the mouth Generally avoided by grazing animals due to bitter taste

8. Distribution Native to southern Asia (Mongolia, Iran, Armenia, Turkestan) Introduced in infested alfalfa seeds 1890s Can find it in 412 counties in 21 western states First documented in 1943 in Quay County

9. Russian Knapweed Shoot biology Root biology Reproductive biology Management options

10. Shoot biology Shoots emerge in early spring from root buds Can form dense stands 100-300 shoots/m2 Shoots densities as low as 11/m2 have significantly reduced yields in crops Infestations can persist for >100 years Can survive in low light areas (under tree canopy in riparian areas) increased leaf area

11. Root biology The main method of spread for Russian knapweed is from adventitious buds and the creeping perennial root system. Roots can grow 6 to 8 feet in one season, and expand radially up to 14 yd2 in two seasons.

12. Seed biology Russian knapweed is not a prolific seed producer. Each shoot can produce 50 to 500 seeds Seeds remain viable in the soil for 2 to 3 years (Beck 2003).

13. Russian Knapweed management Prevention, early detection and eradication are the best management tools, as large infestations are difficult to eliminate. Small establishing infestations require few resources to eradicate and typically resident plants recover from management methods eliminating the need to restore the site. The best management plan includes cultural control combined with mechanical and/or chemical control techniques. A single control strategy, such as mowing or herbicide use, is not sufficient to control old, dense infestations.

14. Common management tools Mechanical Mowing, disking can have some success if integrate with other methods Biological CLASSICAL: Subanguina picridis, Stem/leaf gall nematode. Several others being researched COMPETITION: Healthy, competitive plant community Herbicides Can be effective and economical for large infestations Need to replace open space created