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Diffuse knapweed (Centaut•ea diffusa) <br /> Diffuse knapweed is a biennial plant and sometimes a short-lived perennial that <br /> germinates in fall or early spring,over-winters as a rosette,and bolts and flowers <br /> in the summer.Flowers are typically white,sometimes pink,with spiny bracts <br /> beneath.After flowering,diffuse knapweed sets seed in late summer or fall,after <br /> which the plant breaks off at the base and becomes a tumbleweed spreading seed <br /> as far as the wind will carry the plant.Diffuse knapweed reproduces only by seed, <br /> and the seed can remain viable in the soil for 15 years. <br /> The most effective <br /> herbicides for controlling <br /> A close-up of the diffuse knap,�t�eci hotter diffuse knapweed are <br /> Tordon,Transline,Curtail <br /> and Redeem.Milestone is effective for controlling plants at the rosette <br /> stage. <br /> Numerous insects are available for biological control of diffuse knapweed <br /> and can provide fair to good results.The most effective have been a seed <br /> head weevil Larinus minutes and root weevils Ciphocleonus achates and <br /> Sphenoptera jugoslavic•a.For more detailed information on infestation ' <br /> size and densityto warrant an insect release and for obtaining g insects go to a <br /> Colorado Biological Pest Control Program }yf� ,�1 <br /> Mowing and grazing can suppress populations,but plants will still flower Diffuse knapkkeed ru.eu" <br /> and set seed from a reduced height.Hand pulling and digging,when <br /> feasible,is very effective.If hand pulling or digging plants that have flowered,be sure to bag and dispose the plants to prevent <br /> seed dispersal. <br /> A Top <br /> Spotted knapweed (Centaltrea macidosa) <br /> Spotted knapweed is a short-lived perennial plant that reproduces only by seed.Plants <br /> grow to 3 feet tall and produce pink to purplish flowers with prominent black spots <br /> on the bracts beneath.Spotted knapweed is closely related to diffuse knapweed but is <br /> i <br /> more prevalent at higher elevations.This noxious weed is not common in Larimer <br /> r County but has the potential to thrive here much as it has in other western states and <br /> Canadian provinces.Montana alone reports infestations covering an estimated 5 <br /> s' <br /> million acres. <br /> Because spotted knapweed is <br /> highly invasive and population <br /> levels are currently low in <br /> Larimer County,required <br /> management methods are those <br /> that can result in eradication. <br /> Insect biocontrol,mowing,and <br /> A close-up u: the.patted kuapsc•eed Eov er grazing are not acceptable forms <br /> of management.Required <br /> methods are herbicide <br /> application,digging or hand pulling. <br /> The most effective herbicides for controlling spotted knapweed are Tordon, Spotted kr,ap;�ecd <br /> Transline,Curtail and Redeem.Milestone is effective for controlling plants at <br /> the rosette stage. <br /> Spotted knapweed reproduces only by seed,so mechanical control methods should be conducted prior to seed production.Hand <br />