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alfalfa is an effective competitor only after it is established (i.e., it will not establish in a well-
<br />developed Canada thistle community).
<br />Table 2. Herbicide options for controlling Canada thistle.
<br />All label directions and precautions must be followed.
<br />Do not use herbicides that will damage desirable species. "ae" stands for "acid equivalent."
<br />Herbicide Rate Notes Reference
<br />Picloram, e.g. May be applied on non-crop areas only. Apply whenever
<br />Tordon 22K"" 1 gUacre C. thistle is actively growing, but fall applications particu- 1,2
<br /> larl effective.
<br /> .1 qt piclo-
<br />Picloram + ram/acre 2,4-D may be used on pastures, rangeland, and non-crop
<br />4-D
<br />2 • 1 qt or 1.5- areas. Apply whenever C. thistle is actively growing, but 1,2
<br />, 2.0 ae 2,4- fall applications particularly effective.
<br /> D/acre
<br /> 4-D Cc3 1.5-
<br />2 2,4-D may be used on pastures, rangeland, and non-crop
<br />Escort+2,4-D ,
<br />20 ae/acre areas. 2,4-D should be applied in pre-bud to early bud
<br />" 1,2
<br /> sta e -10-15
<br />tall .
<br /> • /3-1 pt /
<br />Clopyralid,
<br />e.g., Stinger, acre in
<br />spring May be used on non-crop areas only. Most effective
<br />2
<br />Transline • 1 pt /acre in when applied to rosette to bud growth stages.
<br /> fall
<br /> -Apply before bud stage. Use higher rate for dense in-
<br /> festations or under poor growing conditions, e.g., drought.
<br />Clopyralid + 1.2-1.8 Ib ae' May be used on non-crop areas only.
<br />2,4-D, e.g., (or 2-3 gtsz) -Performance may be improved when preceded by 2-3
<br />" 1 2
<br />Curtail per acre mowings. Begin mowing when C. thistle is 12-15
<br />tall,
<br /> repeat ~ 1-mo. intervals. Apply Clopyralid (2-3 qts/acre)
<br /> -1 mo. after 3rd mowing. Follow regimen for 2 consecu-
<br /> tive rs.
<br /> Dicamba can be applied at any time during the growing
<br /> 2 qts/acre season to actively growing plants; however, applications
<br />Dicamba, e.g., when C. this- in the late vegetative to bud stage or in the fall may be
<br />Banvel, Van- tle is in rosette most effective if the plant has 8-12" regrowth. May be 1,2
<br />quish, Clarity stage (early used on pastures, rangeland, and non-crop areas. May
<br /> spring) be most effective when combined with 2,4-D as a split-
<br /> season a lication see below .
<br />2,4-D + 2 qts/acre Split-season treatment: Apply 2,4-D in pre-bud to early
<br />"
<br />dicamba (both) bud stage when C. thistle is -10-15
<br />tall. Apply dicamba 2
<br /> to re rowth in fall.
<br /> Dicamba can be applied at any time during the growing
<br /> season to actively growing plants; however, applications
<br />Dicamba + 2,4-D applied in the late vegetative to bud stage or in the fall may be
<br />2,4-D, e.g., ~ 1.5-2.0 most effective if the plant has 8-12" regrowth. 2,4-D may 1,2
<br />Veteran 720 ae/acre be used on pastures, rangeland, and non-crop areas.
<br /> 2,4-D should be applied in pre-bud to early bud stage
<br /> -10-15" tall .
<br />' http://www.co.larimer.co.us/gublicworks/weeds/managemenUMgtCanadaThistle.htm
<br />z Beck 2000
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