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Deeper tillage such as moldboard plowing,if feasible,can provide 1-2 years <br /> control. <br /> x Mowing effectively suppresses Canada thistle,and in combination with a fall <br /> herbicide application provides best control.To read more about Canada thistle <br /> see the article"Canada Thistle." <br /> smal:stand of Canada th'stle <br /> •Top <br /> Musk thistle (Cccrdtcus nutans) <br /> Musk thistle is a tap-rooted biennial that reproduces only by seed.Plants typically <br /> germinate in late summer or early fall,over-winter as a rosette,bolt and flower in the <br /> spring or early summer,disperse seed in mid-summer.Seed longevity is variable but <br /> can last up to 10 years.Mature plants are 2-8 feet tall.Musk thistle is fairly common <br /> r in Larimer County. <br /> =� Since musk thistle reproduces <br /> only by seed,management <br /> methods should be applied <br /> prior to seed set. <br /> The most effective herbicides <br /> for control of musk thistle are S <br /> A c1<r.c-t.p of the n:,:,k t.i.,tly <br /> Perspective,Milestone, a <br /> Curtail,Redeem,Transline, <br /> Tordon,and Telar.Apply <br /> anytime from rosette stage to early flower.Applications after the early ` <br /> flower stage are not beneficial since the plant can produce viable seed <br /> while dying down. <br /> A seed head weevil,Rhinocyllus con icus,released for control of musk Musk thr.tle ro,e,.tes <br /> thistle,is well dispersed throughout Colorado and further releases are <br /> unnecessary.The impact from this weevil has been cyclic,some years very effective,other years not.Other insect predators are <br /> available,but have only been marginally effective. <br /> Because population levels are low in Larimer County,required management methods are those that result in eradication like <br /> herbicide application,digging or.pulling.Grazing,mowing and insect biocontrol are not acceptable forms of treatment in Larimer <br /> County.When digging or hand pulling it is essential to dig up at least 3-4 inches of the tap-root to prevent re-growth. <br /> A Top <br /> Bull thistle (Cirsium vulgare) <br /> Bull thistle is a tap-rooted biennial that reproduces only by seed.Plants typically germinate in late summer or early fall,over- <br /> winter as a rosette,bolt and flower in the spring or early summer,disperse seed in mid-summer.Seed longevity is variable but can <br /> last up to 10 years.Mature plants are 1.5-6 feet tall.Bull thistle is not common in Larimer County but appears to be spreading. <br /> Since bull thistle reproduces only by seed,management methods should be applied prior to seed set. <br /> The most effective herbicides for control of bull thistle are Perspective,Milestone,Curtail,Redeem,Transline,Tordon,and Telar. <br /> Apply anytime from rosette stage to early flowering.Applications after the early flower stage are not beneficial since the plant can <br /> produce viable seed while dying down. <br />