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