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North Dakota is being threatened by three
noxious weeds that could infest more acreage in the state and at a faster
rate than leafy spurge. Members of this trio include spotted, diffuse,
and Russian knapweed. The knapweeds already infest more acreage than
leafy spurge in Montana and Minnesota, and have been found in over 25
counties in North Dakota. Knapweeds are related to thistles and can
spread even faster. For instance, spotted knapweed infested approximately
25 acres in eight North Dakota counties in 1984; by 1997 it had spread
to more than 1000 acres in 14 counties. Diffuse knapweed can spread
as quickly as spotted knapweed, but Russian knapweed spreads much slower.
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Knapweed infestations
in North Dakota have been found primarily along highways, waterways, railroad
tracks, pipelines and recently constructed utility lines. Knapweed often
spreads to a new site by seed in hay, on vehicles, or in contaminated
seed. Watch for new infestations along any publicly traveled route, where
livestock are fed, or in disturbed areas. Control methods vary depending
on the knapweed species and proper identification is the first step towards
stopping the spread of these noxious weeds.
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People are the
major cause of knapweed spread from one location to another. Inspect vehicles,
hay, gravel, etc. carefully if they have come from a knapweed infested
area. |
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Short-lived perennial or biennial; tap-root.
Black-tipped bracts. Pink flowers, rarely cream colored
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Short-lived perennial or biennial; tap-root.
Spiny or "crab-like" bracts. White to rose, or sometimes purple
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Perennial with black, spreading roots
that form new shoots. Rounded bracts with transparent tips. Pink to lavender
flowers
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