WEED CONTROL

Weed Watch - Spotted Knapweed Spotted in Cass County
                                    
North Dakota is being invaded by a weed species that threatens to
cause more economic, livestock, and wildlife loss than leafy
spurge. This threat is spotted knapweed, a biennial weed first
introduced into the North America in the Pacific northwest from
Europe.     
                                
Spotted knapweed is an aggressive, introduced weed that rapidly
invades pasture, rangeland, fallow and CRP land. The weed is a
prolific seed producer with 1000 or more seeds per plant. Seed
remains viable in the soil five years. It has little grazing
value and eliminates other types of vegetation when it invades.   
                                      
Currently, 19 counties in North Dakota report spotted knapweed at
various levels of infestation ranging from only a few plants to
100 acres or more. The total infestation is approximately 1800
acres, which is a large increase from 1985 when an extensive
survey was conducted and found only 25 acres in 8 counties.       
                             
Spotted knapweed has purple flowers similar to Canada thistle in
color. However, spotted knapweed flowers are surrounded by stiff,
black-tipped bracts and the plant has small pale green leaves and
does not have spines. The plant is easily controlled when first
established, but spreads very quickly making delayed control
efforts time-consuming and expensive. NDSU Extension Service
Circular W-842R contains color photos of spotted knapweed and
control recommendations.  
                                    
People are the major cause of spotted knapweed spread. The weed
is often spread in hay and on vehicle undercarriages. However,
the weed can be spread through wind by the white, soft pappus
attached to the seed. Spotted knapweed is usually first noticed
on disturbed sites like road ditches, railroad right-of-ways,
recently installed utility lines and parking areas, especially
when livestock is being transported.                              
       
All North Dakotans should become familiar with the purple flower
and black bracts of this weed and report infestations to the land
manger and or county weed control officer. If everyone cooperates
in the identification and eradication program, spotted knapweed
will not have an opportunity to become "another leafy spurge."