LVEA in Action
Summer 2004 ____________________________________________________________________________________________
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| Russian knapweed is a
deep-rooted, perennial weed that once established is very difficult and
expensive to control. It is
found in most parts of the state of Nevada and often invades degraded
areas and dominates remaining plant communities.
Russian knapweed prefers sites that have higher precipitation
such as drainages, riparian zones, river bottoms, irrigated fields and
runoff areas. However, once
established, it is extremely drought tolerant. Primarily reproduced through vegetative growth and seed, Russian knapweed can spread quickly. A single plant’s root system, which includes laterally spreading underground shoots, can reach depths of eight feet and expand up to 12 square yards in two growing seasons. The ridged stems are erect, rather stiff branched and one to three feet high. The upper leaves are small and narrow with broken edges. The flowers are thistle-like, solitary, 1/3 to ½ inch in diameter and lavender to white in color. The plant flowers in June to August and seed is produced in later summer to early fall.
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Russian knapweed is a
serious problem in cropland as it significantly reduces economic
returns. It lowers the
quality of hay as feed and can be difficult to treat in existing
alfalfa or other broadleaf crops. The key to controlling
Russian knapweed is to stress the weed and cause it to keep expending
nutrient stores in its root system.
This can be accomplished the most successfully through proper
herbicide use and re-vegetation with an adapted perennial plant.
Without competitive plants, Russian knapweed will re-invade a
site. Perennial grasses
are preferred as competitive plants because they tolerate herbicides
that are effective against the weed.
Several herbicides that have shown their superiority in
controlling Russian knapweed are: picloram (Tordon) and clopyralid
(Stinger, Transline or Curtail). If you find an infestation or need more information about this weed, please call the Churchill County Weed and Mosquito Abatement District at 423-2828.
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