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I Management Cultural control. Combine control methods Into a management system. Maln[alning pastures and rangeland in good condtUon is a primary factor Cor musk thistle management. Favor pasture and range- land grass growth by not over-grazing and fertilizing according to soU testing recommendations. Prevent seed (omratton to successfully manage musk thistle. Mechanlcai control. Musk UtLstle will not tolerate tillage and can be removed easily by severing its root below ground with a shovel or hce. Mowing can effectively reduce seed output !l plants are cut when the terminal head is to the late-[lowerlrtg stage. Gather and burn mowed debrLs to destroy any seed that has developed. Chemical control. Several herbicides are regis- tered 1n pasture, rangeland and noncrop areas fo control musk thistle. Tordon 22K (picJoram), 13arne1 (dicamba), 2,4-D, or 13anvel plus 2,4-D are commonly used. Apply these herbicides in spring or fall to musk th1sUe rosettes. Apply Tordon at 0.125 to 0.25 pound ai/A, liarrvel at 0.5 to 2.0 pounds a1/A 2,4-D at 1.5 to 2.0 pounds al/A or 13anvel plus 2,4-D at 0.5 plus 1.0 pound al/A Cool temperattues pens than 40 F), particularly In fall, may adversely aliect 2,4-D control of musk thistle; therefore, use 2.4-D !n spring. Tordon is largely unaffected by cool temperatures: however,l3anvel can be adversely aBeeted but less than 2,4-D. l3arnel plus 2,4-D works well In spring or Call. Apply arry of these herbicides before musk th1sUe bolls or seed production stlll wID occur. Ally-Escort lmetsu3Curori) ar Te1ar (chlorsulfuroN can be used. Use Telar !n non-clop only and Ally- Escort !n pastures, rangeland or non-crop. Research from Colorado State Untversity and the Unh+ersity oC Nebraska shows Telar or Ally prevents or dramati- cally reduces, vtable seed formation when applied to spring, up to early Rower growth stages. The latest time to apply these herbicides 1s when developed terminal flowers have opened up to the size of a dime or quarter. Apply Telat at 0.75 ountt ai/A; use higher rates for dense lnfestatlons or when residual mrttrol 15 desired. Apply Ally-Escort at 0.3 ounce al/A A good agricultural surfactant at 0.25 percent v/v should be added to Ally-Escort or Telar treahnents or rnntrol is Inadequate. Ally-Escort 1s avallable for pastures and rangeland. Biological control The musk thistle seed head weevil. RfttrtocyUus mrnlcus, can be found throughout Colorado. The female deposits her eggs on the back of developing flowers and corers them wtth masticated leaf tissue. After eggs hatch, Larvae bon Into the (lower and destroy developing seed. The seed head weevil reduces seed production by 50 percent on the average, but !f used alone, 1s not an e$ective manage- ment tool. Certain herbiGdes or mowirng can be combined with the seed head weevil ft these an applied during late IIowering stages. This allows the weevlls to complete their life cycles and Insures their presence >n subsequent growing seasons. The Colo- rado Department of Agatcultun !s hying to establish another weevil. Trichostrncalus ltorridrrs. This weevU attacks the crown area of musk thistle rosettes and kllis or weakens the plant before !t bolts. This weevil J 1 1 1 1 1 1 should soon be wady (or re-distributton throughout Colorado try the Department of Agriculture. Integrating Control Methods An example of how to combine chemical and biological control methods would be to apply herbi- cides at a time that does not interfere with Insect development, that >s, allow insects to complete their life cycle. Another example is to use herbicides in areas that annY senslUve to their use and employ biological control in areas where herbicides one Impractical or environmentally unsafe. Cultural methods that favor desirable plant growth can be combined with c}rerrllcal or biological control by superhnpostng proper gr:ving management, fertility maintenance and seeding.