Musk thistle is a large, spiny biennial with rose-purple flower heads up to 2½ inches wide. The stems are commonly winged with spiny leaf tissue. The plant forms basal rosettes during its first year, which have deeply lobed leaves that are up to 10 inches long and 4 inches wide, and have a prominent, nearly white center vein. During the second year, an upright flowering stalk grows that has smaller, very spiny leaves. The flower heads are mostly solitary and nod at the branch tips. At the base of each flower head are numerous, spine-tipped bracts, ⅛ to ⅜ inch wide, that curve away from the heads. Blooms June through October. A single plant can produce 11,000 seeds, spread by silky parachutes.
Herbicides for Noxious Weeds
| Formulated Product/Acre | Herbicide and lb active ingredient needed/acres | Comments and Limitations |
|---|---|---|
1.5 to 2 at of 4 lb/gal 2,4-D amine, LVE, or mixed formulations | 2,4-D amine (4) 1.5 to 2 | Apply during rosette stage of growth. In spring, apply 2,4-D at 1.5 lb ae/acre. For best control in fall, apply 2,4-D LVE at 2 lb/acre. 2,4-D amine can be applied in fall, if soil moisture is favorable and air temperature exceeds 50°F |
1 to 2.5 oz Chaparral | Aminopyralid (4) + Metsulfuron (2) | Use for broadcast or spot treatment in rangeland, pastures, and CRP. Treat plant in the spring or fall. See label for recommendations for bolted to early bloom stage plants. |
Rate I Cimarron Max | Metsulfuron (2) + Dicamba (4) + 2,4-D (4) | Apply in the spring or early summer before flowering or in the fall. Add NIS or other adjuvant. |
0.25 to 0.5 oz Cimarron Plus | Metsulfuron (2) + Chlorsulfuron (2) | Apply in spring or early summer before flowing or to rosettes in the fall. Apply before the ground freezes. |
2 to 4 pt Curtail | Clopyralid (4)/ 2,4-D (4) 0.095 + 0.5 to 0.19 + 1 | For use on rangeland, permanent grass pasture, CRP, and noncropland. Apply to actively growing rosettes in the spring or fall or to bolted thistles up to the bud stage. |
0.67 pt Dicamba | Dicamba (4) 0.33 | Apply in the spring during the rosette stage of growth. Can be applied for control in fall if soil moisture is favorable and air temperature exceeds 50°F |
0.5 pt Dicamba + 0.75 qt 2,4-D amine or LVE | Dicamba (4) + 2,4-D (4) 0.25 + 0.75 | Apply in the spring during the rosette stage of growth. Can be applied for control in fall if soil moisture is favorable and air temperature exceeds 50°F |
0.25 to 0.50 oz Escort XP or Metsulfuron | Metsulfuron (2) 0.009 to 0.019 | Apply in the spring or fall to rosettes. Add 0.5 lb 2,4-D to enhance activity up to flowering. Note: Do not apply if drought conditions exist at intended time of application. |
1.2 to 1.5 pt GrazonNEXT HL | Aminopyralid (4) + 2,4-D (4) | Use for broadcast or spot treatment in rangeland, pastures, and CRP. Treat plants in the spring during rosette through bolting stage of development or in the fall. |
| 3 to 5 fl oz Milestone | Aminopyralid (4) 0.047 to 0.078 | Use for broadcast or spot treatment in rangeland, pastures, noncropland, and CRP. Treat plants in the spring during rosette through bolting stage of development or in the fall. |
| 4 oz Overdrive | Diflufenzopyr (19) / Dicamba (4) | For use on noncropland, pasture, hay, and rangeland. Apply in the spring to actively growing rosettes or bolted thistles up to the bud stage. Add NIS or MSO. |
| 4 oz Rave | Triasulfuron (2) / Dicamba (4) | Apply in spring to rosette stage or up to 5-inch tall bolted thistles. Add 0.5 lb, 2,4-D (1 pt of 4 lb/gal) for enhanced control. |
0.5 to 1 oz Telar DF | Chlorsulfuron (2) 0.023 to 0.047 | For use on rangeland, permanent grass pasture, CRP, and noncropland. Apply in spring from rosette to pre-bloom stages of growth. Do not allow spray drift to contact nearby crops or other nontarget plants; injury can occur. |
0.5 pt Tordon 22K + 1 qt of 4 lb/gal 2,4-D amine, LVE, or mixed formulations | Picloram (4) + 2,4-D (4) 0.13 + 1.0 | Tordon 22K is a restricted-use pesticide. Apply from rosette up to the flowering stage in spring after soil thawing. |
| 0.5 pt Tordon 22K | Picloram (4) 0.13 | A restricted-use pesticide. Apply during the rosette stage in the fall, before soil freezes. |