Such natural enemies include the musk thistle rosette weevil and the musk thistle flower head weevil (Figures 3 and 4) and a musk thistle rust fungus (Figure 9). As many as 40 larvae have been found per terminal head. Larval feeding can kill a rosette outright or it can change the growth pattern of the thistle, giving rise to a shorter plant that produces fewer flower heads that are smaller and contain less seed. Musk Thistle is biennial, meaning its life cycle lasts over two years. Musk thistle Carduus nutans L. Family: Asteraceae (Composite family) Life cycle: Biennial Native status: Introduced as an ornamental for its showy flowers Habitat: Pastures, roadsides, General description: First year plants form basal rosette up to 2 ft wide; leaves deeply lobed with spine tipped margins. Flower color varies from purple to a deep reddish pink. Biennial thistles spread only by seed (achenes) that are produced in great number by all the noxious species, ran… Seeds mature and can begin dispersing in 7-10 days … Multiple seed heads develop from individual plants. About 70 percent of seeds germinate the first year and 20 percent the second year; the rest either blow away or germinate later. Populations of the musk thistle weevils have increased throughout the state through natural dispersion and through collection and recolonization. Miscellaneous:  A small percentage of musk thistleplants act as annuals, these plants flower later in the summer and are much shorter than two-year old plants. Environmental Impacts The musk and plumeless thistles are completely unpalatable to grazing livestock. This stalk bears the flowers which can produce up to 120,000 wind dispersed seeds per plant. Musk thistle reproduces entirely by seed. Texas Redbud. The pupa rests in an excavated cell in the receptacle, where it transforms into an adult. The first season the plant germinates from seed and produces a rosette of basal leaves. Musk thistle Carduus nutans, musk thistle. The fluffy purplish flowers of thistles are the only visually pleasing part of the plant, but don't be fooled; they carry the seeds that guarantee another year of thistle invasion. 2150 Beardshear Hall Musk thistle, however, can be a problem in fall-planted grains, alfalfa or clover if conditions are favorable for seedling establishment and winter survival. You can determine whether you have infestations of the flower head or rosette weevils by looking for larvae of these insects at the appropriate season (Figure 10). Big leaf Maple. Newly established thistle rosettes are inconspicuous and you may not see them until they bloom the following year. View all agriculture and environment programs, Starting a Small Business: The First Steps, Agricultural systems and natural resources, Agricultural Business and Policy Extension, Veterinary Extension and Continuing Education, Exceed - Regional Economic and Entrepreneurial Development, Mid-America Trade Adjustment Assistance Center, Missouri Procurement Technical Assistance Centers, Missouri Small Business Development Centers, Continuing Medical Education and Physician Lifelong Learning, Tai Chi for Arthritis and Falls Prevention, equal opportunity/access/affirmative action/pro-disabled and veteran employer. The musk thistle weevil lays eggs on the bracts on underside of flower, and covers them with chewed foliage. Biennials, such as musk thistle and tall thistle, germinate in summer and fall, spend the winter as rosettes, then produce many flower heads the next spring. A healthy plant is below. Pratia. The leaf margins of a flowering bull thistle plant (a) are tipped with spines, and the stems have spiny wings. A late-blooming cycle often occurs just prior to frost. When the six-foot tall plants mature, they frequently block access to water and reduce usable land significantly. The eggs are usually laid in the midrib on the underside of rosette leaves or placed directly in the rosette crown. The bolting stage begins when the seed stalk starts to form and continues until the first flower head appears. After overwintering as adults, the weevils emerge in early spring and feed on the leaves of musk thistle rosettes. 1. The disease appears as brown pinpoint pustules first on the leaves (Figure 9) and then on all parts of the musk thistle plant. Apply Escort or Telar up to the early flower growth stage. Help improve lives, communities and economies throughout the state. The site navigation utilizes arrow, enter, escape, and space bar key commands. Biology, identification, distribution and control of musk thistle, including an illustrated life cycle and photos to aid in plant and pest identification. Pasture management practices such as seeding and fertilization to increase grass and forb production increase competition with the thistle and can be substituted for spraying. The first report of an infestation of musk thistle in Missouri came from Palmyra (Marion County) in 1941. Biennials take two growing seasons to complete their life cycle. Musk thistle normally requires two years to complete its life cycle (i.e. Bull thistle gene… Figure 9Musk thistle rust fungus appears as brown pustules on the underside of leaves. The life cycle of musk thistle in Missouri is variable. The key to successful musk thistle control is to prevent seed production. The economic impact of musk thistle is greatest in pastures and rangeland. Occasionally, the plant completes its life cycle in one growing season (i.e. In warmer climates the thistle can have an annual life cycle, in other words, it will send up a stalk the same year it produces the rosette. The seed is disseminated by wind currents and can be carried many miles from its original site. Tab will move on to the next part of the site rather than go through menu items. © 1993 to document.write(new Date().getFullYear()) Curators of the University of Missouri, all rights reserved, DMCA and other copyright information. Biological and Integrated Control of Musk Thistle in Missouri. They are grayish green along the outer edge with a lighter green midrib area. Family: Composite, Asteraceae.. Habitat: Pastures, meadows, wasteland, and roadside ditches. A single taproot develops and stem elongation occur in early May. 3. Musk Thistle Musk thistle dies after it sets seed. This is one of seven noxious weeds for which Nebraska law mandates control. Although it is generally classed as a biennial (two growing seasons needed for a plant to mature), musk thistle can develop as an annual, biennial or winter annual, depending on local environmental conditions. Musk thistle's tolerance to most herbicides increases after it bolts. This approach maximizes thistle control and is least disruptive to the weevils. A third biological control agent for musk thistle is a rust fungus. Moderate infestations of musk thistle reduce pasture yields an average of 23 percent. After seed germination, the plant develops into the rosette stage (Figure 2). The rosette grows and increases in diameter until the onset of cold weather. Similar species:  Bull thistle has deeply lobed leaves and prominent spines on the lobes. The Conservation Services Division provides technical and financial support, leadership and statewide coordination, and regulatory oversight to public/private landowners and agricultural businesses statewide on an array of natural resource management challenges. Musk thistle produces many heads. Figure 7Flower head weevils lay eggs on the bracts of developing flowers. It is more difficult to determine the presence of rosette weevils. State & National Extension Partners. A single plant can produce up to 9,000 seeds. Musk thistle (Carduus nutans L.) was added to the Nebraska noxious weed list in 1959. Seed from the late bloom primarily is responsible for the limited success of seed-feeding wee - vils (Rhinocyllus conicus)introduced for biological control of musk thistle. Musk thistle’s life cycle was accelerated by warming and earlier reproductive phenology and, as a result, musk thistle’s projected annual population growth rate increased. If larvae of the rosette weevil are present, black streaks can be seen where the larvae have moved through the rosette. Larvae take about 25 to 30 days to complete development. Key ID traits:  Margins of leaves often silverish, giving them a frosted appearance. After the larvae have completed their development, they leave the rosette and pupate in the soil. To minimize adverse effects on the flower head weevil, herbicides can be applied from mid-March to late April, mowing can be done in mid-July, and herbicides can be applied again in September and October. Its large, nodding flower heads are distinctive and appear from June to August. Musk thistle (Carduus nutans) is a 3- to 8-foot biennial thistle. Occasionally, the plant completes its life cycle in one growing season (i.e. They stop feeding and begin a resting stage, called pupation, which lasts another eight to 14 days. Bull thistle (Cirsium vulgare) (Figure 2) has been present in Oklahoma for more than 40 years and occurs statewide. Missouri landowners spend between $750,000 and $1 million annually to control musk thistles with herbicides. Tillage easily eradicates rosettes established during the preceding summer or fall. biennial or winter annual). Some rosettes may extend three feet or … All biennial thistles considered noxious are native to Europe or Eurasia, and were introduced into North America as seed contaminants. Flower heads are deep rose, violet, or purple, or occasionally white. It rarely reaches infestation levels that justify treatment, probably because the insects that feed on native Circium spp. A bolted plant is one that has developed an upright stem (Figure 3). It may be necessary to sample several rosettes to determine the level of infestation by the weevil. The problem with mowing musk thistle is that not all the plants in an infestation produce terminal flower heads at the same time. Experimentally applied warming significantly increased survival and growth. Then a fleshy taproot develops, allowing the plant to overwinter. The two weevils are compatible with each other as biological control agents because they do not compete with each other. Thistles that germinate in the spring will spend the entire summer as a rosette, live through the winter, and bolt the next year in May and June. This weed, with its showy, reddish flowers, now occurs throughout the state and in 1979 was declared a noxious weed by Missouri state statute (Figure 1). The life cycle of musk thistle in Missouri is variable. Figure 3The musk thistle rosette weevil feeds on rosette leaves. In second year flower stalk elongates up to 5 ft tall; numerous pink to purple flower heads up to 2 in wide, largest of Iowa’s thistles; head surrounded by sharp bracts. The larvae tunnel into the receptacle, the swollen base of the thistle flower, where they feed (Figure 8). Found sporadically throughout Ohio. Conservation Services. A perennial life cycle means that a weed regrows season after season. Occasionally, the plant completes its life cycle in one growing season (i.e. Musk thistle is primarily a biennial or winter annual species. Identification and Life Cycle Musk thistle (Carduus nutans) is a biennial, although occasionally an annual, in the sunflower family (Asteraceae). The plant dies after all its seeds mature. Native status: Introduced as an ornamental for its showy flowers For this reason, the insect is said to produce only one generation per year in Missouri. These grow along the leaf margins and extend down the branches and stems. Musk thistle was introduced to North America as a garden flower by European colonists. This secretion gives the eggs a dirty, scale-like appearance. Chemical control can be effective if properly timed. Up and Down arrows will open main level menus and toggle through sub tier links. Where the flower head and rosette weevil are considered together, mowing can still be practiced in mid-July, but spraying should be restricted to a narrow period from September to mid-October. Musk thistle produces a basal rosette during the first year. Farmers are usually busy in the spring and may postpone chemical application until they are caught up with field work. Flowering begins in early June and continues until mid-August. They stand tall and strong, like sentries allowing no one to pass. Leaves extend down the stem giving them a 'winged' appearance. Enter and space open menus and escape closes them as well. Find several of the flower heads that formed earliest. Infestations of musk thistle often occur in areas difficult to reach and may escape notice until after flowering. Leaves are deeply and irregularly indented, with a smooth waxy surface or a somewhat hairy surface. On flowering plants, base of leaf extends down stem forming spiny wings. An integrated pest management approach to musk thistle control takes into consideration the life cycle of the musk thistle weevils in relation to the seasonal development, or phenology, of the thistle (Figure 10). The weed is found most commonly along roadsides, railroad rights-of-way and fence borders and in wastelands and pastures. Musk thistle                 Carduus nutans L. Family:  Asteraceae (Composite family) The rosette overwinters and the cold temperature causes the rosette to send up a stalk the next season, flower and produce seed. However, only one-third of the seeds are viable. In second year flower stalk elongates up to 5 ft tall; numerous pink to purple flower heads up to 2 in wide, largest of Iowa’s thistles; … Applications made after the plant bolts are too late for good control. Occasionally, the plant completes its life cycle in one growing season (i.e. Apply herbicides such as Tordon, Milestone, Transline, Perspective, Vanquish/Clarity or 2,4-D to musk thistle rosettes in spring or fall. Musk thistle is primarily a biennial or winter annual species. Since musk thistle seeds are long-lived in the soil, it is important to prevent plants from producing seed until new rosettes are no longer produced. By mid-May, most musk thistles have budded or flowered. Musk Thistle. Reproduction and Spread One plant can set up to 20,000 seeds. General description:  First year plants form basal rosette up to 2 ft wide; leaves deeply lobed with spine tipped margins. Musk Thistle. Although it is generally classed as a biennial (two growing seasons needed for a plant to mature), musk thistle can develop as an annual, biennial or winter annual, depending on local environmental conditions. As with the other thistles, it is attractive to a wide range of insects, and is the foodplant of the caterpillars of the Painted lady butterfly. In late spring, some egg laying can be found in secondary buds. The plant begins flowering in early to mid-May and continues through August. For the best experience on our site, be sure to turn on Javascript in your browser. It undergoes one generation per year. Base of flower heads is flatter than bull or Canada thistle. By 1997 it was detected in 37 counties in Missouri. All rights reserved. Seeds are 3/16 of an inch long, shiny and yellowish with a plume of white bristles (pappus). For example, an annual life cycle means that a weed goes from seed to seed in one growing season or one year. Musk thistle weevils are widely distributed in Missouri. This is the most effective stage at which to inhibit seed production and prevent rebolting. These basal leaves are characterized by having a wide, white midvein and whitish leaf margins and tips. Areas of expertise include agronomy, field crop production and management of corn, soybeans, and... ISU Extension and Outreach Musk thistle is a biennial weed that reproduces only from seed. Musk thistle is a biennial weed. 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. They feed on the underside of rosette leaves by puncturing leaf tissue. Leaves have few hairs, and typically the margins are greyish, giving the plant a 'frosted' look. Perennial Flowers + Moneyplant. biennial or winter annual). Weevil larvae feeding on seed within musk thistle flower head. A major identifiable characteristic of musk thistle is that the outer edge of the leaf is silver in color, while the interior of the leaf is light green. Although the disease does not kill the plant or reduce its seed production, it coexists with the musk thistle weevils and apparently does not interfere with their feeding on the thistle. The emergence of new-generation adults occurs from mid-May until mid-June. A musk thistle rosette is a cluster of leaves in circular form that grows flat on the ground without an upright stem (Figure 2). The adults emerge in July and seek overwintering sites under new musk thistle rosettes and ground litter and in wooded areas, where they will remain dormant until the following year. Rosettes may reestablish any time during the growing season. The rosette weevil is about 1/8 inch long with a narrow snout. If both flower head and rosette musk thistle weevils are present, mow in mid-July and spray rosettes in September and October for best weed control and least harm to the weevils. Musk thistle (Carduus nutans) is easily distinguished from other thistles in the state by its silvery leaf margins, and absence of hairs or fuzz and large, nodding flower heads. For the best experience on our site, be sure to turn on Javascript in your browser. Although treated plants may appear to be injured, with wilted leaves and twisted stems, the plants will nevertheless flower and produce viable seed. In the region of seed development, small, white, grublike larvae should be present if the thistle plant is infested with flower head weevils. Life cycle: Biennial, forming a rosette the first year and producing flowers and seed in the second.. First Year Growth Habit: A basal rosette. Hatching larvae from eggs laid on the rosettes burrow their way to the growing center or crown bud. Biennial thistles, such as musk (Carduus nutans L.), plumeless (Carduus acanthoides L.) and bull thistle [Cirsium vulgare (Savi) Tenore], are not as difficult to control as the perennial thistle species, but spread rapidly and can become severe problems in some areas. There they feed on the meristemic tissues, producing a necrotic area that enlarges and becomes evident by spring. Natives of Europe, the weevils were studied extensively to ensure that they would not damage economic plants in this country. Life cycle Musk thistle can be a biennial, a winter annual, or an annual. Entomologists with the USDA Agricultural Research Service Biological Control of Insects Research Laboratory in Columbia, Missouri, released flower head weevils in 1975 near Marshfield in Webster County; rosette weevils were released in 1979-80. The next spring, new leaves originate from crown buds. If you see incompletely filled flower heads with dead plant tissue in the center, you might suspect that musk thistle weevils are present. life cycle of the musk thistle weevils inThe relation to the seasonal development of musk thistle is shown in Figure 9.The chart shows an integrated control program using proper timing of mechanical and chemical control practices that encourages weevil populations for effective thistle control. The objectives of this study were: (a) to determine the normal life cycle of musk thistle in Nebraska; (b) to determine the variations from the normal life cycle of musk thistle; and (c) to furnish a summary of the phenology for musk thistle in southeastern Nebraska. Figure 2A. Height varies from 2 to 6 or more feet. Figure 1Musk thistle was accidentally introduced into the United States in the late 1800s and is now a noxious weed. Figure 2B. The best time to mow musk thistle is within two days after the terminal flower head blooms. Flower head weevil infestations are easiest to find when the musk thistle is blooming (June). These insects attack the earlier blooms but have completed their life cycle before the last flowers set seed. Leaves are waxy and pale green with few hairs. The life cycle of the musk thistle weevils in relation to the seasonal development of musk thistle is shown in Figure 10 (back page). Biennials take two growing seasons to complete their life cycle. Musk thistle normally requires two years to complete its life cycle (i.e. Biennials require portions of two growing seasons to reproduce. Musk thistle, Carduus nutans L., is a European weed introduced accidentally into the eastern seaboard of the United States in the mid- to late 1800s. Livestock usually won't graze infested areas but occasionally feed on the flower heads. biennial or winter annual). JavaScript seems to be disabled in your browser. summer annual). For intelligent and efficient weed control, some knowledge of the life cycles of weeds is useful. The musk thistle weevil was introduced as a biological control agent in the 1980’s and is common across the state. The larvae of the rosette weevil feed on the underside of the leaves of the rosette and on the leaves and stems of bolted plants; larvae of the flower head weevil feed in the base of the developing flower of the thistle. Left and right arrows move across top level links and expand / close menus in sub levels. Check fencerows, ditch banks and waste areas periodically for musk thistles. Cultural, mechanical, biological and chemical control methods have all been used on musk thistles with varying degrees of success in different parts of the country. Trees-Acacia. The rosette stage will last for the first season of its life and is recognizable by having many prickly leaves which spread out from its center, and which lay low to the ground. The flowers of musk thistle are large, solitary and beautiful. Ames, IA 50011-2031 The large flower heads and broad, showy bracts make this species stand out from the rest, though closely related is Plumeless Thistle (Carduus acanthoides), whose flower heads are rather smaller, with narrow bracts. You will also find 1/8- to 3/8-inch spines on the tips of the leaves. Some flower heads turn brown prematurely because many larvae are feeding in the receptacle or because larvae are feeding in the stem just below the receptacle. Birds, such as Greenfinches and Linnets, also gorge on the seeds it produces. Specific natural enemies of musk thistle can aid in regulating the spread of this weed. Knowing about Musk Thistle and Cherokee Rose life span is important as life cycles vary. Musk thistle produces an average of 10,000 seeds per plant, but under favorable conditions can produce even more. Apply 2,4-D or other registered herbicides to the musk thistle rosettes in either fall or spring. Like most of its close relatives, musk thistle is covered with sharp spines. Combine control methods into a management system for best results.Musk thistle is a… 4. 2. Each female lays an average of 100 eggs during its lifetime. Copyright © 2020 Iowa State University of Science and Technology. The effective eradication of this weed pest from an infested pasture requires dedication and perseverance because of the longevity and viability of seeds (five to seven years) in the soil. Canada thistle is much smaller and leaves are not as deeply lobed. Figure 2After seed germination, a rosette develops. Its status as a weed pest in Missouri was recognized in the early 1960s, when it became abundant in pastures, primarily in northwest and south central Missouri. Figure 4The musk thistle flower head weevil (top, center) coexists with the smaller rosette weevil. Figure 8Flower head larvae feed in the base of the flower head, exposed here. Seeds generally germinate in the fall or spring, but may germinate anytime moisture is sufficient. Yellow Wild Indigo. In areas of the state where the weevils have been present for the longest period of time, a 70-90 percent reduction in thistle population has occurred (Figure 5). It begins it's life as a seedling in spring and will turn into a rosette as the season continues. While grasping a flower head on each side, break it in half. University of Missouri Extension is an equal opportunity/access/affirmative action/pro-disabled and veteran employer. Figure 2C. 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. Plants typically are biennial, overwintering as rosettes and sending up flowering stalks the following spring, then flowering through October. Knowing about Musk Thistle and Cherokee Rose life span is important as life cycles vary. Musk thistle normally requires two years to complete its life cycle (i.e. 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. Musk Thistle Life Cycle. Additionally, mowing on poor soil may actually inhibit the competitive effect of other plants and favor survival of musk thistle seedlings. summer annual). Figure 6Rosette weevil larvae feed on the growing center of the top plant, producing a necrotic area. Few hairs on leaves. The life cycle of a weed is simply its seasonal pattern of growth and reproduction. It spends approximately 90 percent of its life cycle in a vegetative growth stage. The typical biennial musk thistle exhibits itself the first year in the from of a rosette, a cluster of tightly packed leaves laying flat on the ground. The number of larvae per head decreases as more flowers develop. Musk thistle has been reported in nearly every county in Kansas and is found primarily in pastures, rangeland, hay meadows, alfalfa, fallow, roadsides, and waste areas. Mating takes place shortly thereafter, and by the time musk thistles begin to bolt, the females are ready to lay eggs. Nodding Thistle is on the noxious weed list for Minnesota, a … Vegetables + summer annual). Figure 2. Adult weevils emerge from estivation (summer hibernation) in early October. biennial or winter annual). Its larvae feed on developing seed within the flower head. (800) 262-3804, Iowa State University Seeds are dispersed by wind, have a high germination rate under favorable conditions, and may remain viable in … common life cycle is for musk thistle to germinate in the summer, overwinter as a rosette, and begin bolting (seed stalk production) about May 1. The interior of the rosette is normally white. Use Esc key to go back to input search field. summer annual). Field thistle flowers much later in season than musk and other thistles. This thistle is devoid of leaf hairs. Flower head weevils lay eggs on the bracts of developing flowers (Figure 7) and cover each egg with a secretion of chewed plant material. The flower head weevil is about 1/4 inch long. https://www.fs.fed.us/database/feis/plants/forb/carnut/all.html These same adults overwinter and resume egg laying the following spring until about May 1. Flowers are the largest of Iowa's thistles, and have a flat receptacle covered in sharp bracts. Dr. Hartzler also teaches undergraduate classes in weed science and weed identificatio... Rebecca Vittetoe is an extension field agronomist in east central Iowa. Scouting is best performed in March and April by cutting through the rosette of the musk thistle plant. Habitat:  Pastures, roadsides. Educational programs are available for farmers, agribusiness, pesticide applicators, and certified crop advisors. 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