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NOXIOUS WEED DEPARTMENT |
Musk thistle control program |
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Description | Reduction | Control | Herbicides | Biological Control | Pictures |
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*Information provided by County Weed Directors Association of Kansas Musk thistle normally requires two years to complete its life cycle (i.e. biennial or winter annual). Occasionally, the plant completes its life cycle in one growing season (i.e. summer annual). The typical biennial musk thistle exhibits itself the first year in the form of a rosette, a cluster of tightly packed leaves laying flat on the ground. Rosettes vary in diameter from a few inches to three feet. Musk thistle overwinters as a rosette. During the rosette stage (either fall or spring) musk thistle is most susceptible to chemical control. In its second year of growth, the musk thistle plant will leave the rosette stage as its stem elongates (bolts) toward the mature, flowering plant with a large fleshy taproot that is corky and hollow near the ground surface. Chemical control is less effective during the bolted stage and chemical susceptibility continues to decline as the plant reaches maturity. The leaves of the musk thistle are deeply lobed (segmented), hairless, and are dark green with a light green mid-rib. A silver gray leaf margin is characteristic of each spine tipped lobe. The leaf base extends down the stem to give the plant a winged appearance. Musk thistle is the first of the Kansas thistles to bloom in the spring. Flowering begins in mid-May and continues through early July. Each head consists of many tightly packed rose to purple colored flowers encased in a series of spine-tipped, green bracts. The terminal (uppermost) head is 1 1/2 - 3 inches in diameter, solitary, and generally bent over or nodding. The mature plant is generally branched, with each lower branch producing one or more heads. Flowering begins with the terminal head and progresses downward. Musk thistle heads are distinguished by their "powder puff" shape. Other Kansas thistles have "shaving brush" shaped heads. Dispersal of seeds begins approximately 30 days after blooming of the head. Seeds are strawberry colored, oblong, and 1/8 inch in length. The seeds are attached to parachute-like hairs (pappus) which allow for their dispersal by wind currents. The potential for seed production is enormous. Large plants can potentially produce 15,000 seeds with approximately 50% of those being viable. Musk thistle may be found throughout the State with heaviest infestations found in the north eastern one third of the state. The first line of defense against musk thistle should be proper grazing management. Fertilization or cool-season forages is also an important practice in reducing a musk thistle invasion. Purchase feed grain or hay from reputable neighbors or dealers. Properly clean equipment before leaving an invested field. The control of musk thistle shall mean preventing the production of viable seed. Hand Digging: Dig the root at least two inches below ground level and remove all soil. Burying Flowering Heads: Pick heads that are beyond the bud stage and place in a tight container. Avoid scattering seed. Burning Flowering Heads: When burning heads, make sure the heads and seeds are destroyed; burning wet or green heads may leave viable seeds. Mowing: Mow cleanly and closely and repeat as needed for satisfactory control. Shall be approved first by the Franklin County Noxious Weed Director. The following herbicides may be used for cost-share with landowners. Other products labeled and registered for use on this noxious weed in Kansas may be used in accordance with label directions but are not available for cost-share. Apply herbicides when musk thistle plants are in the rosette stage and rapidly growing with favorable soil moisture. For ground applications apply herbicides with 10 to 20 gallons of carrier per acre. Retreat with the herbicides or cultural treatment to prevent seed production and reduce new infestations. 2, 4-D Amine or LV Ester. Apply during rosette stage of growth. 2, 4-D Amine can be used in the fall if the soil moisture is favorable and air temperature exceeds 50 F. Follow label directions and precautions. Chlorsulfuron (Telar). Apply in spring before rosette gets to pre-bloom stages of growth. Follow label directions and precautions. Dicamba (Banvel). Apply in spring during rosette stages of growth. Can be used for control in the fall if the soil moisture is favorable and air temperature exceeds 50 F. Follow label directions and precautions. Picloram (Tordon). Restricted use herbicide. Apply during rosette stage of growth in the spring or fall, prior to soil freeze-up. Follow label directions and precautions. Picloram + 2, 4-D (Tordon + 2, 4-D). Restricted use herbicide. The addition of 1.0 pound of 2, 4-D will improve the consistency of musk thistle control with picloram when environment of biological conditions are not conducive to good herbicide activity. Metsulfuron Methyl (Escort). Use rates depend on the application site. Consult the label and supplemental labels for use directions. Follow label directions and precautions. Any biological control plan must meet the requirements of K.A.R. 4-8-41. |