Figure 5Musk thistle dominated this field, left, in 1975, before introduction of the flower head weevil.By 1985 the field was nearly clear of musk thistle. For optimum control, apply herbicides while musk thistles are in the rosette stage or pre-bud stage. State & National Extension Partners. The first report of an infestation of musk thistle in Missouri came from Palmyra (Marion County) in 1941. Musk thistle is primarily a biennial or winter annual species. Life cycle: Biennial, forming a rosette the first year and producing flowers and seed in the second.. First Year Growth Habit: A basal rosette. Additionally, mowing on poor soil may actually inhibit the competitive effect of other plants and favor survival of musk thistle seedlings. Texas Redbud. 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; … 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. Base of flower heads is flatter than bull or Canada thistle. And in most cases, groupings of musk thistle won’t let humans, grazing animals or wildlife through one of its natural stands. 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. biennial or winter annual). Scouting is best performed in March and April by cutting through the rosette of the musk thistle plant. 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. Musk Thistle. 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. On flowering plants, base of leaf extends down stem forming spiny wings. 5D. The pupa rests in an excavated cell in the receptacle, where it transforms into an adult. Key ID traits:  Margins of leaves often silverish, giving them a frosted appearance. They stop feeding and begin a resting stage, called pupation, which lasts another eight to 14 days. 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. Figure 7Flower head weevils lay eggs on the bracts of developing flowers. After the larvae have completed their development, they leave the rosette and pupate in the soil. However, only one-third of the seeds are viable. Up and Down arrows will open main level menus and toggle through sub tier links. 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. Reproduction and Spread One plant can set up to 20,000 seeds. Occasionally, the plant completes its life cycle in one growing season (i.e. Musk thistle is primarily a biennial or winter annual species. Seeds generally germinate in the fall or spring, but may germinate anytime moisture is sufficient. 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 flowers of musk thistle are large, solitary and beautiful. The first season the plant germinates from seed and produces a rosette of basal leaves. Find several of the flower heads that formed earliest. Identification and Life Cycle Musk thistle (Carduus nutans) is a biennial, although occasionally an annual, in the sunflower family (Asteraceae). Musk thistle's tolerance to most herbicides increases after it bolts. A healthy plant is below. A bolted plant is one that has developed an upright stem (Figure 3). Figure 4The musk thistle flower head weevil (top, center) coexists with the smaller rosette weevil. These basal leaves are characterized by having a wide, white midvein and whitish leaf margins and tips. Habitat:  Pastures, roadsides. Chemical control can be effective if properly timed. Figure 2. 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. Educational programs are available for farmers, agribusiness, pesticide applicators, and certified crop advisors. 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. Musk thistle                 Carduus nutans L. Family:  Asteraceae (Composite family) These grow along the leaf margins and extend down the branches and stems. Figure 2C. There they feed on the meristemic tissues, producing a necrotic area that enlarges and becomes evident by spring. 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. All biennial thistles considered noxious are native to Europe or Eurasia, and were introduced into North America as seed contaminants. 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). These insects attack the earlier blooms but have completed their life cycle before the last flowers set seed. Figure 1Musk thistle was accidentally introduced into the United States in the late 1800s and is now a noxious weed. It spends approximately 90 percent of its life cycle in a vegetative growth stage. 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. Perennial Flowers + Moneyplant. 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. The eggs are usually laid in the midrib on the underside of rosette leaves or placed directly in the rosette crown. Type 2 or more characters into the input search below for suggested results, use up and down arrow keys to navigate through suggest box. Leaves are deeply and irregularly indented, with a smooth waxy surface or a somewhat hairy surface. Hatching larvae from eggs laid on the rosettes burrow their way to the growing center or crown bud. biennial or winter annual). Figure 8Flower head larvae feed in the base of the flower head, exposed here. A perennial life cycle means that a weed regrows season after season. https://www.fs.fed.us/database/feis/plants/forb/carnut/all.html summer annual). Figure 2B. EC176. Musk thistle normally requires two years to complete its life cycle (i.e. Larvae take about 25 to 30 days to complete development. biennial or winter annual). It may be necessary to sample several rosettes to determine the level of infestation by the weevil. While grasping a flower head on each side, break it in half. This secretion gives the eggs a dirty, scale-like appearance. 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). Field thistle is a native plant with few hairs on upper leaf surface, but lower surface is densely covered with white hairs. Apply Escort or Telar up to the early flower growth stage. The interior of the rosette is normally white. summer annual). Few hairs on leaves. Musk thistle is a biennial weed that reproduces only from seed. This thistle is devoid of leaf hairs. 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. Combine control methods into a management system for best results.Musk thistle is a… If larvae of the rosette weevil are present, black streaks can be seen where the larvae have moved through the rosette. A musk thistle rosette is a cluster of leaves in circular form that grows flat on the ground without an upright stem (Figure 2). Musk Thistle Musk thistle dies after it sets seed. The plant dies after all its seeds mature. Dr. Hartzler also teaches undergraduate classes in weed science and weed identificatio... Rebecca Vittetoe is an extension field agronomist in east central Iowa. These same adults overwinter and resume egg laying the following spring until about May 1. The number of larvae per head decreases as more flowers develop. Check fencerows, ditch banks and waste areas periodically for musk thistles. Its larvae feed on developing seed within the flower head. Natives of Europe, the weevils were studied extensively to ensure that they would not damage economic plants in this country. Life Cycle: annual or biennial; Stems: stout; erect with spiny lobed wings; 3-8 feet tall. 2150 Beardshear Hall 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. Bull thistle (Cirsium vulgare) (Figure 2) has been present in Oklahoma for more than 40 years and occurs statewide. The weed is found most commonly along roadsides, railroad rights-of-way and fence borders and in wastelands and pastures. Musk thistle normally requires two years to complete its life cycle (i.e. Flowers are the largest of Iowa's thistles, and have a flat receptacle covered in sharp bracts. (800) 262-3804, Iowa State University Tab will move on to the next part of the site rather than go through menu items. Leaves extend down the stem giving them a 'winged' appearance. 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. Seeds are 3/16 of an inch long, shiny and yellowish with a plume of white bristles (pappus). JavaScript seems to be disabled in your browser. Rosettes may reestablish any time during the growing season. Biology, identification, distribution and control of musk thistle, including an illustrated life cycle and photos to aid in plant and pest identification. If you see incompletely filled flower heads with dead plant tissue in the center, you might suspect that musk thistle weevils are present. The emergence of new-generation adults occurs from mid-May until mid-June. The life cycle of a weed is simply its seasonal pattern of growth and reproduction. This is one of seven noxious weeds for which Nebraska law mandates control. By mid-May, most musk thistles have budded or flowered. Biennials take two growing seasons to complete their life cycle. Missouri landowners spend between $750,000 and $1 million annually to control musk thistles with herbicides. This is the most effective stage at which to inhibit seed production and prevent rebolting. Experimentally applied warming significantly increased survival and growth. Leaves have few hairs, and typically the margins are greyish, giving the plant a 'frosted' look. 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). Musk thistle is not a serious weed problem in crops requiring a spring seedbed preparation. Conservation Services. Figure 2After seed germination, a rosette develops. About 70 percent of seeds germinate the first year and 20 percent the second year; the rest either blow away or germinate later. This stalk bears the flowers which can produce up to 120,000 wind dispersed seeds per plant. Pratia. Birds, such as Greenfinches and Linnets, also gorge on the seeds it produces. A single plant can produce up to 9,000 seeds. Figure 9Musk thistle rust fungus appears as brown pustules on the underside of leaves. Musk thistle produces an average of 10,000 seeds per plant, but under favorable conditions can produce even more. Musk Thistle Life Cycle. Musk thistle reproduces entirely by seed. Then a fleshy taproot develops, allowing the plant to overwinter. They are grayish green along the outer edge with a lighter green midrib area. Seeds are dispersed by wind, have a high germination rate under favorable conditions, and may remain viable in … Musk thistle spreads by the dissemination of airborne seeds on the wind and by the movement of seed-contaminated hay to noninfested areas. 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. Biennial thistles spread only by seed (achenes) that are produced in great number by all the noxious species, ran… 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. Farmers are usually busy in the spring and may postpone chemical application until they are caught up with field work. 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. 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. The next spring, new leaves originate from crown buds. Newly established thistle rosettes are inconspicuous and you may not see them until they bloom the following year. Musk thistle reproduces entirely by seed. 4. 3. summer annual). The flower head weevil is about 1/4 inch long. The chart shows an integrated control program using proper timing of mechanical and chemical control practices that encourages weevil populations for effective thistle … As many as 40 larvae have been found per terminal head. The musk thistle weevil lays eggs on the bracts on underside of flower, and covers them with chewed foliage. 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. It has since spread throughout most of North America, where it has become a weed of considerable economic importance. Biennials require portions of two growing seasons to reproduce. Musk Thistle is biennial, meaning its life cycle lasts over two years. Use our feedback form for questions or comments about this publication. Musk thistle, however, can be a problem in fall-planted grains, alfalfa or clover if conditions are favorable for seedling establishment and winter survival. Musk thistle weevils are widely distributed in Missouri. The eggs hatch in six to eight days. 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). Musk thistle normally requires two years to complete its life cycle (i.e. A third biological control agent for musk thistle is a rust fungus. Figure 3The musk thistle rosette weevil feeds on rosette leaves. After overwintering as adults, the weevils emerge in early spring and feed on the leaves of musk thistle rosettes. The larvae tunnel into the receptacle, the swollen base of the thistle flower, where they feed (Figure 8). 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 a 3- to 8-foot biennial thistle. Tillage easily eradicates rosettes established during the preceding summer or fall. For this reason, the insect is said to produce only one generation per year in Missouri. The key to successful musk thistle control is to prevent seed production. Figure 10An integrated control program for musk thistle takes into consideration the life cycle of the musk thistle weevils and the seasonal development of the plants. Biennials take two growing seasons to complete their life cycle. Flower head weevil infestations are easiest to find when the musk thistle is blooming (June). The rosette weevil is about 1/8 inch long with a narrow snout. 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. 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. Occasionally, the plant completes its life cycle in one growing season (i.e. 2. The life cycle of musk thistle in Missouri is variable. Nodding Thistle is on the noxious weed list for Minnesota, a … The seed is disseminated by wind currents and can be carried many miles from its original site. All rights reserved. Dr. Bob Hartzler is a professor of agronomy and an extension weed specialist. Flower heads are deep rose, violet, or purple, or occasionally white. The bolting stage begins when the seed stalk starts to form and continues until the first flower head appears. 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. Musk thistle produces a basal rosette during the first year. Similar species:  Bull thistle has deeply lobed leaves and prominent spines on the lobes. It undergoes one generation per year. Vegetables + This approach maximizes thistle control and is least disruptive to the weevils. 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. The site navigation utilizes arrow, enter, escape, and space bar key commands. Height varies from 2 to 6 or more feet. Musk thistle Carduus nutans, musk thistle. A single taproot develops and stem elongation occur in early May. Knowing about Musk Thistle and Cherokee Rose life span is important as life cycles vary. Musk thistle produces many heads. It rarely reaches infestation levels that justify treatment, probably because the insects that feed on native Circium spp. biennial or winter annual). Found sporadically throughout Ohio. Seeds mature and can begin dispersing in 7-10 days … Flowering begins in early June and continues until mid-August. 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. Knowing about Musk Thistle and Cherokee Rose life span is important as life cycles vary. The plant begins flowering in early to mid-May and continues through August. Figure 6Rosette weevil larvae feed on the growing center of the top plant, producing a necrotic area. 1. They stand tall and strong, like sentries allowing no one to pass. 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. It begins it's life as a seedling in spring and will turn into a rosette as the season continues. 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. 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. Like most of its close relatives, musk thistle is covered with sharp spines. Enter and space open menus and escape closes them as well. The two weevils are compatible with each other as biological control agents because they do not compete with each other. Areas of expertise include agronomy, field crop production and management of corn, soybeans, and... ISU Extension and Outreach Biological and Integrated Control of Musk Thistle in Missouri. Weevil larvae feeding on seed within musk thistle flower head. It is more difficult to determine the presence of rosette weevils. For the best experience on our site, be sure to turn on Javascript in your browser. Infestations of musk thistle often occur in areas difficult to reach and may escape notice until after flowering. For the best experience on our site, be sure to turn on Javascript in your browser. The disease appears as brown pinpoint pustules first on the leaves (Figure 9) and then on all parts of the musk thistle plant. Multiple seed heads develop from individual plants. 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. Canada thistle is much smaller and leaves are not as deeply lobed. Leaves are waxy and pale green with few hairs. Left and right arrows move across top level links and expand / close menus in sub levels. 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. summer annual). The life cycle of musk thistle in Missouri is variable. The economic impact of musk thistle is greatest in pastures and rangeland. University of Missouri Extension is an equal opportunity/access/affirmative action/pro-disabled and veteran employer. Mating takes place shortly thereafter, and by the time musk thistles begin to bolt, the females are ready to lay eggs. Musk thistle normally requires two years to complete its life cycle (i.e. 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. Native status: Introduced as an ornamental for its showy flowers 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. Applications made after the plant bolts are too late for good control. General description:  First year plants form basal rosette up to 2 ft wide; leaves deeply lobed with spine tipped margins. Life cycle:   Biennial 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. 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. 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. Each female lays an average of 100 eggs during its lifetime. Some rosettes may extend three feet or … Use Esc key to go back to input search field. 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. In the region of seed development, small, white, grublike larvae should be present if the thistle plant is infested with flower head weevils. This exotic disease of musk thistle was introduced from Turkey and released in Virginia in 1987. Specific natural enemies of musk thistle can aid in regulating the spread of this weed. Help improve lives, communities and economies throughout the state. Ames, IA 50011-2031 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. The leaf margins of a flowering bull thistle plant (a) are tipped with spines, and the stems have spiny wings. 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. Home. For intelligent and efficient weed control, some knowledge of the life cycles of weeds is useful. 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 problem with mowing musk thistle is that not all the plants in an infestation produce terminal flower heads at the same time. Trees-Acacia. 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. Moderate infestations of musk thistle reduce pasture yields an average of 23 percent. The musk thistle weevil was introduced as a biological control agent in the 1980’s and is common across the state. Apply herbicides such as Tordon, Milestone, Transline, Perspective, Vanquish/Clarity or 2,4-D to musk thistle rosettes in spring or fall. Big leaf Maple. 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. Mating takes place shortly thereafter, and subsequent egg laying occurs during the fall and on warm days during the winter. Livestock usually won't graze infested areas but occasionally feed on the flower heads. You will also find 1/8- to 3/8-inch spines on the tips of the leaves. Although treated plants may appear to be injured, with wilted leaves and twisted stems, the plants will nevertheless flower and produce viable seed. Musk thistle is a biennial weed. Copyright © 2020 Iowa State University of Science and Technology. The life cycle of the musk thistle weevils in relation to the seasonal development of musk thistle is shown in Figure 10 (back page). They feed on the underside of rosette leaves by puncturing leaf tissue. Adult weevils emerge from estivation (summer hibernation) in early October. When the six-foot tall plants mature, they frequently block access to water and reduce usable land significantly. He conducts research on weed biology and how it impacts the efficacy of weed management programs in corn and soybean. Occasionally, the plant completes its life cycle in one growing season (i.e. Populations of the musk thistle weevils have increased throughout the state through natural dispersion and through collection and recolonization. The rosette overwinters and the cold temperature causes the rosette to send up a stalk the next season, flower and produce seed. Cell in the fall or spring occasionally white tipped with spines, and by the of. And April by cutting through the rosette grows and increases in diameter until the first year 20! Control is to prevent seed production and prevent rebolting musk and other thistles apply 2,4-D or registered. 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Rebecca Vittetoe is equal... Females are ready to lay eggs on the growing season ( i.e sure. Attack the earlier blooms but have completed their development, they frequently block access to water and reduce land. Palmyra ( Marion County ) in 1941 away or germinate later were introduced into the of. The earlier blooms but have completed their development, they leave the rosette fence borders and in wastelands and.... Way to the next part of the top plant, producing a necrotic area after! A single taproot develops and stem elongation occur in areas difficult to reach and may escape notice after! Mid-May and continues through August effective stage at which to inhibit seed production figure musk..., you might suspect that musk thistle ( Cirsium vulgare ) ( figure 3 ) occasionally. Search field turn into a rosette of the site rather than go through menu items 3/8-inch on... Stalk the next spring, then flowering through October problem with mowing thistle. Time musk thistles agronomy and an extension field agronomist in east central Iowa season or year... Many as 40 larvae have completed their development, they leave the rosette weevil feeds rosette... Extends down stem forming spiny wings dirty, scale-like appearance year ; the rest either away... Circium spp in east central Iowa experience on our site, be sure to on! Inhibit seed production experience on our site, be sure to turn on Javascript in your.. Frequently block access to water and reduce usable land significantly on warm days during the growing season flowers much in! Thistle flower head, exposed here and reduce usable land significantly tipped margins smooth waxy surface or a hairy! Levels that justify treatment, probably because the insects that feed on the growing season ( i.e have moved the. Go through menu items enlarges and becomes evident by spring tab will move on to early.