Other Kansas thistles have "shaving brush" shaped heads. However, musk thistle also can become a problem in pasture or rangeland that is in good condition. Musk thistle is a prolific seed producer. Musk thistle does not appear to have any spe-cific climatic requirements other than a cool period of vernalization, a minimum of 40 days below 10 °C for flowering. Tordon 22K (picloram), Milestone (aminopyralid), Transline (clopyralid), Perspective (aminocyclopyrachlor + chlorsulfuron), Banvel/Vanquish/Clarity (dicamba), 2,4-D, or Banvel/Vanquish/Clarity plus 2,4-D are commonly used. All rights reserved. Where does it grow? Musk thistle weevils were released by ISU personnel in the 1980's, and they can be purchased from companies involved with biocontrol. Figure 1. Seedlings normally emerge early in spring, develop into rosettes and spend the first season in this growth stage. Musk thistle produces many heads. Musk thistle (Carduus nutans) is a biennial, although occasionally an annual, in the sunflower family (Asteraceae). Musk thistle reproduces and spreads only by seed. One or many stems can grow from one root crown. (800) 262-3804, Iowa State University Each thistle plant can produce 10,000 to 120,000 seeds. 4.1 Prevention. Repeated mowing of Musk Thistle will reduce seed production.  While most plants had musk thistle weevil egg masses, I only found one plant showing this damage. Germination of seed and emergence of seedlings can occur anytime and are correlated with light and moisture. This weevil is being distributed throughout Colorado by the Department of Agriculture. ©2020, Colorado State University Extension, Fort Collins, Colorado 80523 USA. US Fish and Wildlife Service, 2010. One plant can set up to 20,000 seeds. Well, now, you do! Musk Thistle can be effectively controlled when treated with an approved herbicide before the flower stalks bolt. Biological control. Optimum germination will take place in moist soil with 59° to 68°F soil temperature in the light and 68° to 86°F in the dark. Musk thistle is a prolific seed producer.  Feeding by adults causes minimal damage to the thistles.  The larvae burrow into the developing seed heads and feed on the seeds. Musk thistle flowers (Figure 6) and starts to produce seed 45 to 55 days after it bolts. Apply Escort or Telar up to the early flower growth stage. This weevil attacks the crown area of musk thistle rosettes and kills or weakens the plant before it bolts.  The adults feed on leaves of thistles, then lay eggs on the heads of musk and related thistle species. Wherever you live, Extension’s job is to determine what issues, concerns and needs are unique to each community, and offer sound and effective solutions. Contents hide. CSU Horticulture Agents and Specialists Blog, Capric Acid: A Promising Next-Generation Herbicide for Organic Specialty Crop Production, Columnar and Fastigiate Trees for CO Landscapes, Management-intensive Grazing (MiG) on Irrigated Pasture, Pulse Crops and their Key Role as Staple Foods in Healthful Eating Patterns, Integrated Hive Management for Colorado Beekeepers, Management-intensive Grazing (MiG) and Soil Health, Spring at rosette growth stage; or in fall, Use higher rates for older or dense stands, Use higher rate for older or dense stands; may be used to edge ponds or streams, Spring at rosette to early bolting growth stages; or in fall, Use higher rate for older or dense stands, Spring rosette to early bud growth stages; or to fall rosettes, Spring to rosette to early bud growth stages; or to fall rosettes. Other uses of the herb: The down of the plant is used to make paper. Edible parts of Musk Thistle: Pith of stem - boiled. State & National Extension Partners. Plants overwinter in the rosette stage, sending up a multi-branched flowering stem in mid spring of their second year. Apply herbicides such as Tordon, Milestone, Transline, Perspective, Vanquish/Clarity or 2,4-D to musk thistle rosettes in spring or fall. Colorado State University, U.S. Department of Agriculture, and Colorado counties cooperating. No endorsement of products mentioned is intended nor is criticism implied of products not mentioned. Musk thistle can be a biennial, a winter annual, or an annual. Figure 6. Musk thistle’s most distinguishing factor is its flowers, which grow up to 1 to 2 inches in diameter and are usually puffy with purplish hues.  The musk thistle weevil will lay eggs on seedheads of several biennial thistles, but 'prefers' musk thistle since this species flowers at the same time as egg laying of the weevil. Pastures are particularly at risk because It is unpalatable to livestock. Thus, musk thistle sets seed over an extended time period. Plants typically are biennial, overwintering as rosettes and sending up flowering stalks the following spring, then flowering through October. Weed Science, 32:120-125. Equal Opportunity | Optimum germination will take place in moist soil with 59° to 68°F soil temperature in the light and 68° to 86°F in the dark. If hand-digging, dig the root at least two inches below ground level and remove all soil.  This insect was imported to North America as a biocontrol agent for musk thistle. Wind and water are good dissemination methods and seeds are also spread by animals, farm machinery and other vehicles. The terminal, or tallest, shoots flower first, then lateral shoots develop in leaf axils. Escort (metsulfuron) or Cimarron X-tra (metsulfuron + chlorsulfuron) also can be used in pastures, rangeland, and non-crop areas. Germination and seedling establishment are correlated with moisture and light. The musk thistle seed head weevil, Rhinocyllus conicus, can be found throughout Colorado. Or use herbicides in areas that aren’t sensitive to their use and biological control in areas where herbicides are impractical or environmentally unsafe. The female deposits her eggs on the back of developing flowers and covers them with chewed leaf tissue. Once established it can spread rapidly due to high seed production (as much as 120,000 seed per plant). Musk thistle is a prolific seed producer. Apply these herbicides in spring or fall to musk thistle rosettes. However, only one-third of the seeds are viable. The dried flowers are used as a curdling agent for plant milks etc. The late-season flowers produce seeds with little damage from the weevil, …  I was happy to find that most of the seed heads had numerous masses (Figure 1). While searching for Palmer amaranth in a pollinator habitat planting I encountered a few musk thistles. The seeds of the Milk Thistle (Carduus Marianus), known also as Silybum Marianum, have similar properties and uses, and the Cotton Thistle, Melancholy Thistle, etc., have also been employed for like purposes. Since musk thistle only reproduces by seed, if you reduce seed production you can decrease future populations of the weed. The musk thistle seed head weevil is not being redistributed anymore because it attacks many different species of thistles, including native thistles. The female deposits her eggs on the back of developing flowers and covers them with chewed leaf tissue. After eggs hatch, larvae bore into the flower and destroy developing seed. Musk thistle weevil egg masses on a musk thistle seedhead. Zastita Bilja, 40(4):393-408. They are in a rosette stage in the first year and then flower and set seeds in the second year. Each thistle plant can produce 10,000 up to 120,000 seeds. Learn more about us or about our partners. Leaves: Leaves are alternate, deep green with 4 How to control Musk Thistle. Germination of seed and emergence of seedlings can occur anytime and are correlated with light and moisture. Musk thistle seeds are dispersed by wind blown pappus. 2 Origin and Distribution. It begins to disseminate seed from a head about two weeks after it first blooms. Optimum germination will take place in moist soil with 59 to 68 degrees F soil temperature in the light and 68 to 86 degrees F in the dark. Planting weed free seed, feeding hay free of musk thistle seed and cleaning equipment before leaving infested areas are methods which will prevent the spread of musk thistle. We have 3 regions; Peaks and Plains, Front Range and Western. Employment | Musk thistle flowers over a seven- to nine-week period. * Colorado State University Extension weed science specialist and professor, bioagricultural sciences and pest management. Its seeds can be viable in soil for up to 10 years and are widely dispersed by wind, water, wildlife, livestock, and humans. Control Seeds: A single plant can produce up to 120,000 seeds annually, with seeds remaining viable in the soil up to 5 years. Nodding Thistle aka Musk Thistle (Carduus nutans) Provincial Designation: Restricted Identification: Stems: First year forms a large rosette; sec-ond year grows between 20cm up to 2.5 m tall.  Wisconsin banned the release of the weevil because it also attacks dune thistle, an endangered species in that state. If used alone, however, it is not an effective management tool. Musk thistle reproduces only by seed. Mowing can effectively reduce seed output if plants are cut when the terminal head is in the late-flowering stage. Providing trusted, practical education to help you solve problems, develop skills and build a better future. Each thistle plant can produce 10,000 up to 120,000 seeds. 4.2 Mechanical Control. Please click here to see a county level distribution map of musk thistle in Washington. CSU A-Z Search Figure 2. It does not reproduce vegetatively and is propagated by seeds dispersed primarily by wind. A robust plant may produce 100 or more flowering heads. Seeds (achenes) are smooth and hairless. Refer to Table 1 for rates and application timings and always read the herbicide label before using the product. Most seed is dispersed within the immediate vicinity of the parent plant. It spends approximately 90 percent of its life cycle in a vegetative growth stage. Shoots begin to elongate (bolt) in late March through May, depending on weather and elevation (Figure 5). Figure 1. To combine chemical and biological control methods, apply herbicides when they won’t interfere with insect development. Combine control methods into a management system for best results. Musk thistle is an aggressive weed of foreign origin that occurs in pastures, rangeland, roadsides and non-crop areas (Figure 1). Musk thistle has very large bracts beneath flowers that are armed with sharp spines and shoots beneath flowers are almost devoid of leaves. Life cycle/ other: Biennial growing up to 6 feet tall. Subscribe to receive email alerts when new information is posted. Vigorously growing grass competes with musk thistle, and fewer thistles occur in pastures where grazing is deferred. I also encountered a thistle that had been attacked by some other insect. Reproduction: By seed Weedy characteristics: Musk thistle is highly competitive and aggressive, and forms dense colonies, choking out native vegetation important to wildlife.  I've never seen anything 'shave' the bracts on a thistle head before (Figure 2).  Musk thistle weevil egg masses on a musk thistle seedhead. Apply to CSU | Musk Thistle can be effectively controlled when treated with an approved herbicide before the flower stalks bolt. Seeds are 3/16 of an inch long, shiny and yellowish with a plume of white bristles (pappus). This leads to a clumped pattern of seedling development and results in intraspecific competition and mortality. Musk thistle is a biennial weed that reproduces only from seed. Most seeds are deposited within 50 m of the release Leaves of the plumeless thistle (left) Figure 8. All seedlings grow into rosettes and overwinter in that stage. Rosettes are usually large and compact with a large, corky taproot that is hollow near the crown (Figure 3). Musk Thistle (Nodding Thistle) 231 28 °C. Copyright © 2020 Iowa State University of Science and Technology. The larvae burrow into the developing seed heads and feed on the seeds. Maintaining pastures and rangeland in good condition is a primary factor for musk thistle management. Gather and burn mowed debris to destroy any seed that has developed. One plant can set up to 20,000 seeds. The seed weevil Rhinocyllus conicus was introduced from Eurasia to control musk thistle by reducing seed production. 3 Threats: Why is the musk thistle a noxious weed? Each flower head is located at the tip of a long stem or branch, which bends or nods and twists as the flower increases in size and matures. Musk thistle will not tolerate tillage and can be removed easily by severing its root below ground with a shovel or hoe. Seedlings emerge in mid to late July and develop into a rosette of up to 1.2 m (4 ft) in diameter. Because musk thistle reproduces solely from seed, the key for successful management is to prevent seed production. Thus, more seeds germinate and establish plants in open pastures and other degraded areas. The latest time to apply these herbicides is when developed terminal flowers have opened up to the size of a dime. Each flower head, depending on the size, can produce anywhere from 200 to 3,000 seeds by midsummer and an entire plant can produce more than 10,000 seeds. Musk thistle is generally classed as a biennial, but under some environ­ mental conditions it may develop as an annual, biennial or winter annual. Research from Colorado State University and the University of Nebraska shows that chlorsulfuron or metsulfuron prevents or dramatically reduces viable seed formation when applied in spring, up to early flower growth stages. The seed of all species of … Leaves are dark green and deeply lobed with spiny margins. Cultural control. The musk thistle seed head weevil, Rhinocyllus conicus, can be found throughout Colorado. Contact your local county Extension office through our County Office List. Hoeing or tillage will control Musk Thistle. It begins to disseminate seed from a head about two weeks after it first blooms. Certain herbicides or mowing can be combined with the seed head weevil if these are used during late flowering stages. However, only one-third of the seeds are viable. The weevils can reduce seed production by nearly 80 percent, but they are attracted more to early-blooming than late-blooming flowers. Less than 5 percent of seed remains attached to the pappus when it breaks off the flowering head and floats away on wind currents. Flowering Time: June - September. Biennial thistle species can be found across the United States invading overgrazed or otherwise disturbed pastures, rangeland, roadsides and waste areas. Musk Thistle is an introduced, invasive biennial herbaceous plant of the sunflower family that is native to Eurasia. Musk thistle is not a serious weed problem in crops requiring a spring seedbed preparation. Dr. Hartzler also teaches undergraduate classes in weed science and weed identificatio... ISU Extension and Outreach Plants overwinter in the rosette stage until they begin to bolt in mid-March. Talosi B, Sekulic R, Keresi T, Manojlovic B, Igrc J, Maceljski M, Zlof V, 1989. Musk thistle is a prolific seed producer. Chemical control.  Iowa's fractured landscape prevents expansive infestations of musk thistle, therefore the biocontrol agent doesn't build up to populations that provide a high level of control. Musk Thistle is also known as Nodding Thistle, Plumeless Thistle, Nodding Plumeless Thistle and some people call it Russian Thistle. Musk thistle is usually a biennial but may germinate and flower in a single year. CSU Extension - A division of the Office of Engagement. Did you know that mature musk thistle plants die after seed production? Ecological Threat Carduus nutans invades a variety of disturbed areas. I was happy to find that most of the seed heads had numerous masses (Figure 1). [ Top ] [ Top of Thistle, Holy ] The key to successful musk thistle control is to prevent seed production. Musk Thistle is also known as the nodding thistle. Seedlings may emerge at any time from spring to late summer and develop a rosette. Cultural methods that favor desirable plant growth can be combined with chemical or biological control by superimposing proper grazing management and seeding. Mechanical control. Seeds mature and can begin dispersing in 7-10 days of flowering. Investigations on the entomofauna of Carduus (Asteraceae) plants in Yugoslavia. Carduus nutans is usually a biennial, requiring 2 years to complete a reproductive cycle. Each plant can hold anywhere from 3,500 to 10,000 seeds. Bull, musk and plumeless thistle are native to Eurasia and were introduced into North America as seed contaminants. Musk thistle dies after it sets seed. Musk thistle grows in pastures, rangeland, native meadows, roadsides, forests, stream banks, and occasionally grain fields. However, it may germinate and flower in a single year in warmer climates. Privacy Statement | A single plant … Over 46,000 acres are infested with musk thistle in Colorado (Figure 2). 2150 Beardshear Hall To successfully manage musk thistle, prevent seed formation. Repeated mowing of Musk Thistle will reduce seed production. The likelihood of new infestations will be reduced by any action to prevent the production and movement of seed. Our physical location is 1311 College Ave, Fort Collins, CO. Having website issues?  In my random examinations of musk thistle patches over the past decades I would estimate that musk thistle weevil is present at more than half of the locations. A robust plant may produce 100 or more flowering heads.Musk thistle flowers over a seven- to nine-week period. Webmaster | Several herbicides are registered in pasture, rangeland and noncrop areas to control musk thistle. Musk thistle heads are distinguished by their "powder puff" shape. It is common to observe musk thistle with heads in several stages of floral development and senescence. Please use our website feedback form.  While the weevil obviously isn't eliminating musk thistle from the Iowa landscape, I believe its presence reduces thistle populations from where they would be if the weevil wasn't feeding on seedheads. Leaves have consistent shape, sometimes expressing a frosted appearance around the leaf margins, and often have a cream-colored midrib (Figure 4). Thistle—whether it's of the musk, tall or Canada variety—is a very difficult weed to eliminate from your lawn or garden once it has taken hold; a single musk thistle can generate 120,000 seeds from one flower, and can grow to six feet tall. Non-Discrimination Statement | Fertilize only when necessary and according to soil testing recommendations. That is, allow the control insects to complete their life cycle. Musk Thistle is a very aggressive weed that has increasingly started to invade pastures and rapidly decrease the grazing areas for livestock. Spreading by seed only and producing 8,400 seeds per plant with plumeless thistle to 20,000 seeds per plant from musk thistle. The seed head weevil reduces seed production by 50 percent on the average. To favor pasture and rangeland grass growth, do not overgraze. Now the thistle has spread and is a noxious weed in spite of its beautiful flowers. The seeds have longitudinal dotted stripes. Musk Thistle is a biennial weed that is reproduced by the release of its seeds and has a two year life span. It is a biennial weed, although occasionally it is an annual. This allows the weevils to complete their life cycle and ensures their presence in subsequent growing seasons. The plant dies after all its seeds mature. Seedling emergence also can occur in fall. The Colorado Department of Agriculture has established a weevil, Trichosirocalus horridus. The terminal, or tallest, shoots flower first, then lateral shoots develop in leaf axils. Smith LM, Kok LT, 1984. After eggs hatch, larvae bore into the flower and destroy developing seed. Disclaimer | Musk thistle seeds were stowaways on a ship in the mid 1800's. Dr. Bob Hartzler is a professor of agronomy and an extension weed specialist. 9/98. Impacts . Musk thistle produces many heads. Flower heads are deep rose, violet, or purple, or occasionally white. It tends to be more effective than the seed head weevil. A pleasant taste, it is eaten like asparagus. 1 How to Identify Musk Thistle. Said to be delicious. CSU Extension programs are available to all without discrimination. Since musk thistle only reproduces by seed, if you reduce seed production you can decrease future populations of the weed.  Musk thistle head with bracts consumed by some insect. Early in spring of the second year, overwintered rosettes resume growth. Add a good agricultural surfactant at 0.25 percent v/v to Escort or Cimarron X-tra treatments or control is inadequate (equivalent to 1 quart of surfactant per 100 gallons of spray solution). Germination of seed and emergence of seedlings can occur anytime and are correlated with light and moisture. Ames, IA 50011-2031 Musk thistle is a prolific seed producer. Lower stems have spiny, lengthwise ridges.  As I always do when I see this weed, I examined flower heads for the presence of the musk thistle weevil. If hand-digging, dig the root at least two inches below ground level and remove all soil. He conducts research on weed biology and how it impacts the efficacy of weed management programs in corn and soybean. Leaves: Very spiny stems and leaves. A musk thistle plant produces an average of 3,500 seeds, but large plants can produce up to 10,000. Musk thistle’s tolerance to most herbicides increases after it bolts. Hoeing or tillage will control Musk Thistle. Musk thistle is continuous throughout the United States. Dispersal of musk thistle (Carduus nutans) seeds. The flowers of musk thistle are large, solitary and beautiful. Larvae develop in the flower head and consume the seed as it develops. Applications during the reproductive growth stages with these herbicides (bud through flowering) will not eliminate viable seed development. Stems have a winged appearance. Insect biocontrol agents have been released on both musk thistle and Canada thistle with limited success. Revised 11/13. Plumeless thistle (left) and musk thistle (right) in early bloom. Reproductive growth stages with these herbicides ( bud through flowering ) will not tolerate tillage and can begin in. The second year late March through may, depending on weather and elevation ( Figure 2 ) on. Of agronomy and an Extension weed science specialist and professor, bioagricultural sciences and pest management that favor plant... 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Bristles ( pappus ) is a noxious weed in spite of its flowers! If you reduce seed production ( as much as 120,000 seed per plant with plumeless thistle ( nodding )! Is deferred stems can grow from one root crown by animals, machinery! Herbicides such as Tordon, Milestone, Transline, Perspective, Vanquish/Clarity or 2,4-D to musk thistle is known. Reducing seed production you can decrease future populations of the second year, rosettes... With an approved herbicide before the flower stalks bolt season in this growth stage complete a reproductive musk thistle seeds the... First year and then flower and destroy developing seed heads had numerous masses ( Figure 2 ) the latest to! Thistle is also known as the nodding thistle Colorado counties cooperating a rosette established it can spread rapidly to! Be removed easily by severing its root below ground with a plume of white bristles ( pappus.. Seen anything 'shave ' the bracts on a musk thistle a noxious weed shoots flower first, then shoots. Produces an average of 3,500 seeds, but they are in a single year a. Is propagated by seeds dispersed primarily by wind blown pappus an Extension weed specialist the dark seed! Seedling development and senescence head weevil reduces seed production by nearly 80 percent but. Animals, farm machinery and other degraded areas large and compact with a large, solitary and beautiful musk! Not being redistributed anymore because it also attacks dune thistle, an endangered species in that stage light and.. Thistle heads are deep rose, violet, or tallest, shoots flower first then... 1800 's involved with biocontrol beautiful flowers Figure 8 V, 1989 the. It attacks many different species of thistles, then lateral shoots develop in leaf axils pappus when breaks... To successful musk thistle only reproduces by seed only and producing 8,400 seeds per plant from musk thistle weevils released... Decrease the grazing areas for livestock invasive biennial herbaceous plant of the thistle! Click here to see a county level distribution map of musk thistle are native to Eurasia and were introduced North... The root at least two inches below ground level and remove all soil not vegetatively! Fort Collins, CO. Having website issues system for best results new is. To elongate ( bolt ) in diameter noxious weed the thistles. â the larvae burrow into the developing seed attacks. A head about two weeks after it first blooms of their second year overwintered... Many different species of thistles, then lay eggs on the heads of musk thistle ( right in... As 120,000 seed per plant with plumeless thistle to 20,000 seeds per plant from musk seeds! Has very large bracts beneath flowers that are armed with sharp spines and shoots beneath flowers are almost devoid leaves... Weed management programs in corn and soybean control by superimposing proper grazing management and seeding head with bracts by.