W-1411 (Revised)

Identification and Control of INVASIVE AND TROUBLESOME WEEDS in North Dakota

Rodney G. Lym, Professor of Weed Science NDSU Department of Plant Sciences Andrea J. Travnicek, Natural Resources Specialist

N.D. Agricultural Experiment Station NDSU Extension Service

Reviewed and reprinted October 2012 his publication was made possible by Photo credits collaboration of the authors, the North All photos in the publication are by Dakota State University Extension Rodney G. Lym, North Dakota State University, T except as noted below. Service and the North Dakota Department of Page 8. Black henbane plant, rosette and Agriculture, with funding from the U.S. Forest pineapple-shaped fruit courtesy of Weeds of Service for printing. Th is publication is intended the West, Tom Whitson, editor. to help land managers properly identify and Flower photograph courtesy of Washington control noxious and invasive weeds found in State Noxious Weed Control Board. the state. Th e current list of 11 noxious weeds Page 10. Photos from Richard Old, XID Services Inc. are included, as well as species listed by various Page 14. Common tansy photos courtesy of counties as noxious. Other species included are Celestine Duncan, Weed Management either invasive weeds found in bordering states Services, Helena, Mont. with the potential to move into North Dakota or Page 18. Downy brome infestation photo courtesy are commonly misidentifi ed native species that of Leslie J. Mehrhoff , IPANE. Panicle photograph courtesy of J.C. Schou, do not require control eff orts, such as the native Biopix.dk thistles. Ligule photograph from Virginia Tech Weed Guide. Control recommendations are current at Page 22. Halogeton photos courtesy of Blake publication, but options change rapidly. Before Schaan, North Dakota Department of beginning any management program, please Agriculture, Bismarck, N.D. consult with your local county Extension agent Page. 24. Hoary cress photos from Richard Old, and/or weed offi cer for the latest chemical, XID Services Inc. cultural and biological control recommendations. Page 28. Russian knapweed bracts courtesy of Steve Dewey, Utah State University. Chemical control recommendations are updated Page 30. Spotted and diff use knapweed bracts annually and printed in the “North Dakota Weed courtesy of Steve Dewey, Utah State University. Control Guide,” Extension publication W-253, Page 32. Kochia seedling courtesy of Richard and are updated more frequently on the Web at Zollinger, North Dakota State University. www.ndsu.edu/weeds. Pages 34 and 36. Insect photos from Biological Control of Leafy Spurge CD, USDA-APHIS For the latest in biological control options, and USDA-ARS, TEAM Leafy Spurge’s IPM contact the North Dakota Department of information series No. 1. Agriculture and/or the local staff of the U.S Page 50. Marsh sowthistle fl ower photo from Department of Agriculture -Animal and Plant Richard Old, XID Services Inc. Health Inspection Service in Bismarck. Page 52. St. Johnswort photo courtesy of Corie Lund, Selfridge, N.D. Page 66. Photos from Richard Old, XID Services Inc. Pages 70 and 71. Toadfl ax photos courtesy of Steve Dewey, Utah State University.

2 WEEDS Absinth wormwood ...... 4 Baby’s breath ...... 6 Black henbane ...... 8 Chamomile, false and scentless ...... 10 Common burdock ...... 12 Common tansy ...... 14 Dame’s rocket ...... 16 Downy brome ...... 18 Field bindweed ...... 20 Halogeton ...... 22 Hoary cress ...... 24 Houndstongue ...... 26 Knapweed, Russian ...... 28 Knapweed, spotted and diffuse ...... 30 Kochia ...... 32 Leafy spurge ...... 34 Milkweed, common and showy ...... 38 Orange hawkweed ...... 40 Poison ivy ...... 42 Purple loosestrife ...... 44 Saltcedar ...... 46 Sowthistle, annual and spiny ...... 48 Sowthistle, perennial and marsh ...... 50 St. Johnswort ...... 52 Thistle, bull ...... 54 Thistle, Canada ...... 56 Thistle, Flodman ...... 60 Thistle, musk ...... 62 Thistle, plumeless ...... 64 Thistle, Scotch ...... 66 Thistle, wavyleaf ...... 68 Toadfl ax, Dalmatian and yellow ...... 70 Yellow starthistle ...... 74

3 ABSINTH WORMWOOD (Artemisia absinthium L.)

4 ABSINTH WORMWOOD

State Noxious Weed List: Yes. Why is this plant a concern? Absinth wormwood is a member of the sagebrush family, Absinth wormwood causes economic losses by reducing which is easily recognized by the strong sage odor. Th e available forage, tainting the milk of cattle that graze it, plant also is known as American or common wormwood, and medically as a pollen source for allergies and asthma. mugwort or madderwort, and wormwood sage. Unlike Absinth wormwood can reduce forage production severely other plants in the sagebrush family, absinth wormwood in pasture and rangeland and is especially troublesome dies back to the root crown each winter, with new shoots when land is overgrazed. Allergy suff erers should avoid emerging each spring. Absinth wormwood is grown in walking through absinth wormwood infestations when the herb gardens for the sage fl avor of the leaves. Th e young plant is fl owering in late July and August. fl ower heads are the source of aromatic oil used to prepare vermouth and absinth. Th e oil of absinth wormwood is also an active ingredient in antiseptic liniments. How do I control this plant? Identifi cation and growth form: Chemical. A variety of auxin-type herbicides, including products that contain clopyralid Absinth wormwood is a perennial fragrant forb or herb. (Stinger, Transline or Curtail), dicamba Th e plant commonly grows 3 to 5 feet tall at maturity. (various), Milestone (aminopyralid), 2,4-D, Absinth wormwood is woody at the base and regrows from Tordon (picloram) and glyphosate (various), the soil level each spring from a large taproot. Leaves are will control absinth wormwood. Th ese light to olive green, 2 to 5 inches long and divided two or herbicides should be applied when the plant three times into deeply lobed leafl ets. Leaves and stems are is at least 12 inches tall and actively growing. covered with fi ne, silky hairs that give the plant a grayish Herbicides applied too early in the growing appearance. Flower stalks appear at each upper leaf node season generally result in poor control. and produce numerous yellow fl ower heads 1/8 inch in Herbicides applied from late June until mid- diameter, which appear from late July through mid-August August have given better residual control the in North Dakota. Each fruit contains one seed, which is following growing season than either spring or less than 1/16 inch long, smooth, fl attened and light gray- fall treatments. If a fall treatment is desired, the brown. Th ese small seeds are scattered easily by wind, plants should be mowed in early to midsummer water and animals, and in hay. Absinth wormwood is a to promote active regrowth and to improve prolifi c seed producer but also can spread by short roots. herbicide coverage. Th e plant is most oft en found on dry soils, in overgrazed pasture and rangeland, wastelands and roadsides. Cultural. Livestock generally will not graze absinth wormwood except in early spring. Mowing and cultivation do not control this weed. Biological. No biological control agents or pathogens are available for this weed.

5 BABY’S BREATH (Gypsophila paniculata L.)

6 BABY’S BREATH

State Noxious Weed List: No. Why is this plant a concern? Baby’s breath is an ornamental plant of Eurasian origin Baby’s breath forms dense stands and displaces desirable introduced to the U.S. in the 1800s. Th e plant is a member grasses and forbs. Because of the large taproot and the of the Pinks or Carnation family and is used by the ability to produce millions of seeds in a small area, this fl oral industry as a fi ller in bouquets. Th e plant escaped plant is diffi cult to remove once it has established in an cultivation and now infests pasture and rangeland in area. Baby’s breath has been listed as a noxious weed in several areas of the West. several Western states.

Identifi cation and growth form: Baby’s breath is a perennial with widely branching stems. How do I control this plant? Th e plant oft en grows to 3 feet tall and is easily identifi ed Chemical. Baby’s breath can be controlled by the presence of many small white fl owers. Th e leaves with herbicides that contain metsulfuron occur in pairs of up to 4 inches long and end with a point. (Escort or Ally) applied during the bolt to Th e number of leaves decreases with increasing plant prefl ower growth stage. height and during fl owering. Th e fl owers are small, about 1/8 inch, and generally white and fi ve lobed, oft en with a Cultural. Hand-pulling this weed is not purple midstripe. Flowering occurs from late June to late practical because of the large taproot. Baby’s August in North Dakota. breath has not become a problem in cropland that is cultivated. Seeds are black, with two to fi ve contained in capsules, and resemble pepper. Th e seeds can germinate in 10 to 15 days Biological. No biological control agents or and plants grow rapidly. Each plant can produce 10,000 or pathogens are available for this weed. more seeds, which are spread when the branches dry, break off and are moved in the wind similar to Russian thistle and kochia. Th e plant has a large, deep taproot that allows it to grow well in dry and poor soil conditions.

7 BLACK HENBANE (Hyoscyamus niger L.)

8 BLACK HENBANE

State Noxious Weed List: No. Why is this plant a concern? Black henbane is native to Europe and was cultivated Black henbane contains alkaloids (hyoscyamine, hyoscine as a medicinal and ornamental plant. In 1670, the plant or scopolamine, and atropine) that have caused occasional escaped cultivation in the United States and became livestock poisoning. Th e plant is not usually grazed by sparingly naturalized by 1859. Black henbane has since animals unless more palatable forage is unavailable. All spread throughout much of the United States, particularly parts of the plant, including the seeds, contain the alkaloids in the Northeast, Midwest and the Rocky Mountains. that can be toxic to humans and animals if eaten. Even just Two alkaloids in black henbane tissues (hyoscyamine and smelling the fl owers can cause headaches and nausea in scopolamine) are useful sedative or anti-spasmodic drugs some people. when used under controlled conditions.

Identifi cation and growth form: How do I control this plant? Black henbane is an annual or biennial plant that can range Chemical. Herbicides recommended for in height from 1 to 3 feet. Rosette leaves are alternate and black henbane control include 2,4-D, dicamba have petioles almost as long as the leaf blades. Stems of (various), Tordon (picloram) and glyphosate. mature plants are erect, leafy, thick, coarse and widely Herbicides should be applied prior to fl owering branched. Leaves are alternate, oblong to ovate, coarsely to prevent seed production. toothed to shallowly lobed and grayish green. Th e foliage is covered with fi ne, sticky hairs and has a foul odor. Flowers Mechanical. Hand pulling, cutting or digging are funnel-shaped, fi ve-lobed, brownish yellow with dark small infestations of black henbane can be purple veins, and arranged in long, leafy, spikelike clusters. eff ective. Wear gloves and protective clothing Fruit of the plant is pineapple shaped, approximately 1 inch when handling these plants. Disking or plowing long, and contains hundreds of tiny, black seeds. should be repeated annually because seeds can persist in the soil for an extended period of Seeds germinate and develop a rosette with a large, whitish time. branched taproot the fi rst growing season. During the second growing season, the plant bolts and fl owers from Biological. No biological control agents or June to August. Th e plant produces hundreds of seeds pathogens are available for this weed. from July to October that can remain viable for fi ve years or more.

9 FALSE and SCENTLESS CHAMOMILE (Matricaria chamomilla L. and Matricaria maritima L.)

State Noxious Weed List: No. False chamomile (Matricaria chamomilla L.) and scentless chamomile (M. maritima L.) are members of the aster family and have fl owers that resemble the common daisy. Some taxonomists place these plants in the genius Anthemis. Both plants are native to Eurasia, are considered naturalized in the northern Great Plains and are common in the region. Th e most obvious diff erence between the two species is the pleasant aroma of false chamomile, while, as the name implies, scentless chamomile has very little odor when crushed.

False chamomile

False chamomile Scentless chamomile (from NRCS plants database) (from NRCS plants database)

Scentless chamomile

10 FALSE and SCENTLESS CHAMOMILE

False chamomile has been used for medicinal purposes for Several other members of the “daisy” family, hundreds of years and most oft en is consumed today as including pineapple-weed [Matricaria matricarioides chamomile tea, which reportedly has relaxation benefi ts. (Less.) Porter], oxeye daisy (Chrysanthemum As with many homeopathic medicines, chamomile is leucanthemum L.) and dog fennel or mayweed credited with curing a variety of aches and illnesses, chamomile (Anthemis cotula L.), also can become including soothing and calming of nerves, reducing weedy. Of these species, oxeye daisy has been the infl ammation and aching muscles, and reducing hay most invasive and is included on several state and fever, asthma and morning sickness. Today chamomile provincial noxious weed lists. commonly is found in air fresheners, cosmetics, insect repellents and potpourri.

How do I control these plants? Identifi cation and growth form: Chemical. Today, chamomile species can Both chamomile species are annual herbs and have be controlled easily with any sulfonylurea white daisylike fl owers. False chamomile blooms from herbicide such as Ally, Cimarron or Escort May through August, and scentless chamomile blooms (metsulfuron) and Telar (chlorsulfuron). somewhat later from June through September. Plants Bromoxynil plus MCPA and Tordon (picloram) grow 6 to 18 inches tall and commonly are found in wet also provide good chamomile control. sites, road ditches, old gardens and weedy (waste) areas. Scentless chamomile fl owers tend to be larger (1 to 1.5 Mechanical. Hand-pulling can be an inches across) than false chamomile (0.5 to 1 inch across). eff ective control method in small infestations Seeds are approximately 2 millimeters long, dark brown, of chamomile. Mowing early in the growing with three ribs on one side and a broad brown central area season or before plants fl ower will reduce on the other. Both plants have very fi nely divided leaves populations but should be repeated oft en. from 0.75 to 2.3 inches long, but scentless chamomile Shallow tillage is recommended during hot, dry generally has more leaves and appears more bushy than weather. false chamomile. Biological. Several biological control agents have been researched for scentless chamomile Why is this plant a concern? control. Th e seed-head weevil, Omphalaplon hookeri, feeds on developing seeds of the False chamomile was a candidate for the North Dakota plant, thereby reducing seed production. Th e state noxious weed list in the late 1970s and early 1980s stem-boring weevil, Microplontus edentulous, because the weed was spreading fast in cropland, especially feeds on the interior of the stem and produces in the north-central region of the state. Many farmers were hollow areas that reduce the vigor of the plant. concerned because false chamomile was tolerant to all Rhopalomyia tripleurospermii, the scentless herbicides then available for use in crops. However, with chamomile gall midge, forms a gall on the the introduction of Glean (chlorsulfuron), landowners plant, which acts as a nutrient sink that can had an eff ective herbicide for false chamomile control. interrupt and stunt the growth of the plant. Th is plant is listed on several county noxious weed lists. Research still is being conducted on these Spring and fall-emerging plants can reduce wheat yields biocontrol agents to predict eff ectiveness in by 20 percent to 60 percent if left unattended. In addition, reducing plant population. scentless chamomile has poor nutrition value and is not palatable to livestock. 11 COMMON BURDOCK [Arctium minus (Hill) Bernh.]

12 COMMON BURDOCK

State Noxious Weed List: No. Why is this plant a concern? Common burdock, also referred to as wild rhubarb, is a Th e plant is a host to powdery mildew and root rot that member of the Asteraceae or sunfl ower family. Common can spread to economically important plants. Burs of burdock is native to Europe and now is established common burdock can become entangled in the wool of throughout much of North America. A tea once was made sheep and signifi cantly damage the quality. Burs also can from the roots to treat gout and rheumatism. Th e plant become entangled in the hair of livestock, allowing seeds is able to spread to new areas by seeds that are found to be distributed to new areas. Th e burs can cause eye within burs of the plant that cling to hair, fur or clothing of disease, mouth sores and skin infections. In addition, milk passing animals or people. products may become tainted if the plant is grazed in large quantities. Identifi cation and growth form: Common burdock has been used as a medicinal herb; however, the plant has been listed as a poisonous plant Common burdock oft en is found growing along roadsides due to its diuretic eff ects. Th e bristles of the plant also may and ditch banks and in pastures and waste areas. Burdock cause localized allergic reactions for some individuals. is a taprooted biennial that reproduces only by seed. In the fi rst year of growth, the plant forms a rosette of large, heart-shaped, thickly hairy leaves similar to rhubarb. Burdock plants bolt in the second year of growth and grow How do I control this plant? 3 to 10 feet tall. Leaves of the plant are alternate and large with the broadest leaves located at the base. Leaves are dark Chemical. Burdock is controlled easily by green above and whitish green and woolly-hairy beneath herbicides such as 2,4-D, dicamba (various) with margins that are toothed or wavy. Flowers of the plant and Escort (metsulfuron). However, the plant are pink, lavender, purple or white and 0.75 inch across. usually grows in areas diffi cult to reach with Numerous fl ower heads present are borne in leaf axils or spray equipment. Herbicides are most eff ective at the end of branches. Th e heads are enclosed in a prickly when applied in the fi rst year during the rosette bur that is composed of numerous smooth or woolly bracts growth stage of the plant. that are tipped with hooked spines. Cultural. Hand-pulling or digging can be an Th e head, or bur, of the fl ower breaks off and scatters the eff ective control method for small infestations seeds. Achenes are gray to brown, mottled, oblong, about if conducted prior to seed production. 0.25 inch long, fl attened and slightly curved. Flowering and Th e plant will not survive in areas that are seed production occur from July to September. One plant tilled. Mowing or cutting can eliminate seed is capable of producing 15,000 to 60,000 seeds. production if conducted aft er the plant has bolted but prior to fl owering. Biological. Th e burdock moth Metzneria lappella Zeller provides some control of seed production. Th e larvae feed on burdock seed but damage varies greatly from year to year since the number of healthy larvae per bur ranges widely. Th e adults emerge in late June to early July and have pale brown wings approximately 0.5 inch across.

13 COMMON TANSY (Tanacetum vulgare L.)

14 COMMON TANSY

State Noxious Weed List: No. Why is this plant a concern? Common tansy, also referred to as garden tansy, golden Common tansy is an aggressive plant that can form dense buttons and bitter buttons, is a member of the Asteraceae vegetative colonies on disturbed sites and generally is or sunfl ower family. Common tansy is native to Europe found on roadsides, fence rows, pastures, vacant lands, and fi rst was introduced to the United States as early stream bank, and waste areas. Disturbances can promote as the 1600s as an ornamental plant and for medicinal the colonization and spread of the plant. Common tansy purposes. Th e plant contains alkaloids that can be toxic reduces overall pasture productivity because the plant to humans and livestock if consumed in large quantities. displaces desirable grasses and forbs and animals are However, animals rarely ingest common tansy due to the reluctant to graze it. In addition, unpleasant tasting milk strong smell of the plant. Illnesses in humans have been may result when dairy cattle graze the leaves of common reported aft er hand pulling, suggesting toxins may be tansy. Wildlife habitat also is aff ected negatively by the absorbed through unprotected skin. Common tansy still is plant. used in some medicines and is listed in the United States Pharmacopoeia as a treatment for colds and fever.

How do I control this plant? Identifi cation and growth form: Chemical. Herbicides for common tansy Common tansy is an aromatic perennial forb or herb control include Escort (metsulfuron) and Telar that commonly grows from 1.5 to 6 feet tall. Th e plant (chlorsulfuron). Chaparral (aminopyralid plus reproduces both by seed and creeping rootstocks. Roots metsulfuron) works well when infestations of the plant are fi brous and produce rhizomes. Stems of of common tansy also include thistle species. the plant are purplish-red. Leaves are alternate, smooth to Herbicides may be most eff ective when applied slightly pubescent, 2 to 10 inches long and 1.5 to 3 inches in the spring during early bud development. wide, and deeply divided into numerous narrow, toothed segments that appear fernlike. Glandular dots on the leaves Cultural. Hand-pulling or digging may of the plant produce the strong, unique odor of the plant. provide control for small infestations of Flowers of the plant are yellow, 0.25 to 0.5 inch across common tansy if the entire root system is and buttonlike in fl at-topped, dense clusters. Each head is removed. However, gloves and protective composed of mainly yellow disk fl owers that are arranged clothing should be worn to prevent absorption at the stem top in a fl at-top cluster in which the outer of toxins through the skin. Mowing can reduce fl owers bloom first. Flowering typically occurs from July to seed production if conducted during the bud September. Flower heads turn brown and maintain their stage; however, plants are able to regrow from shape at seed set. Seeds are yellowish brown with short rootstock. fi ve-toothed crowns. Biological. No biological agents or pathogens Common tansy sometimes is confused with tansy are available for this weed. ragwort (Senecio jacobaea L.). However, tansy ragwort is nonaromatic, has ray fl owers and does not have the sharp, toothed leaves found on common tansy.

15 DAME’S ROCKET (Hesperis matronalis L.)

Fall rosette

16 DAME’S ROCKET

State Noxious Weed List: No. Why is this plant a concern? Dame’s rocket is an escaped ornamental from Eurasia and Even though this common garden fl ower has been in the most oft en found along roads, streams, near woods and in U.S. since colonial times, it is now becoming invasive thickets. Th e fi rst introductions to North America began in many areas of the north-central Plains, especially in in the 1660s and the plant is now considered naturalized. woody areas. Dame’s rocket is in the same family as garlic However, infestations have been increasing rapidly in the mustard, an invasive plant that has invaded woody areas north-central states. and forests in neighboring states such as Minnesota and Wisconsin. Dame’s rocket aggressively competes with native species and has been listed as a noxious weed by the Identifi cation and growth form: USDA. Dame’s rocket is a biennial or occasionally short-term perennial herb in the mustard family. Th e plant resembles phlox, but has four petals, not fi ve. Th e plant grows 2 to 4 feet tall; the stems are erect and oft en branched. Leaves How do I control this plant? are alternate, lanceolate, sharply toothed and pubescent. Chemical. Herbicides used for mustard Dame’s rocket fl owers are found from early May through control in cropland such as MCPA and June, fragrant and generally purple but occasionally pink 2,4-D will kill Dame’s rocket and can be used or white. Seeds are produced in long pods typical of the in wooded areas as long as the herbicide is not mustard family. Dame’s rocket overwinters as a rosette. applied to the tree bark. Typical pasture and rangeland weed control herbicides such as Tordon, dicamba and Transline will not control Dame’s rocket. Cultural. Hand-pulling or digging Dame’s rocket is an eff ective control measure. Seeds remain in the soil for several years, so sites should be revisited each year to keep the plant from reestablishing. Biological. No biological control agents or pathogens are available for this weed.

17 DOWNY BROME (Bromus tectorum L.)

18 DOWNY BROME

State Noxious Weed List: No. Why is this plant a concern? Downy brome is native to the Mediterranean region and is Downy brome can thrive in a variety of habitats and the thought to have been introduced fi rst near Denver, Colo., plant quickly displaces desirable plant communities and as a contaminant in packing material. Th e plant now is lowers plant diversity. Downy brome can be a ready fuel distributed widely throughout North America. Downy source for fi res because the plant grows in high densities brome oft en is found as a contaminant in grass and crop and dries down very early in the season. Downy brome is seed and is diffi cult to separate from the desirable species. palatable to livestock but only for a brief period during the spring and early summer. Th e seeds have long awns that may cause sores in the mouth and eyes of livestock that Identifi cation and growth form: graze it and reduce wool values when it attaches to sheep Downy brome is an annual or winter annual grass that can as they walk through an infested area. Downy brome can range in height from 4 to 30 inches. Seedlings are bright become especially weedy in winter wheat. green with conspicuously hairy leaves. Stems are erect, slender and glabrous or slightly hairy. Foliage and seed heads of mature plants oft en change color from green to purple to brown or tan as the plant dries. A single downy How do I control this plant? brome plant can be comprised of one or two tillers or as Chemical. Several herbicides, including many as 20 tillers. Infl orescence is dense, slender, usually Everest (fl ucarbazone), Olympus drooping, one-sided, and 2 to 6 inches in length. Spikelets (propoxycarbazone) and Beyond (imazamox), are nodding, slender and up to 0.75 inch long. Plants have are labeled for downy brome control in fi ve to eight oretsfl per spikelet. Long, straight awns are cropland. Plateau (imazapic) applied in the attached to fl orets that are 3/8 to 5/8 inch long and are fall will control downy brome in pasture and usually purple at maturity. rangeland. Seedlings germinate in the fall or winter at very high Mechanical. Hand-pulling small infestations rates as soon as moisture conditions are favorable. Downy may eliminate current seed production. brome grows rapidly until late fall when the soil freezes, Disking is oft en ineff ective, unless tilled 4 although above-ground growth may continue during warm to 6 inches deep in order to bury seeds and or rainy conditions. Th e root system oft en will continue prevent germination. Mowing may reduce plant to develop throughout the winter. In the spring, the plant production but seeds already may be viable and develops rapidly and produces heads in late April to early plants may regenerate new culms if conducted May, fl owers within a week and produces seed by mid to during the early growth stage. late June. Downy brome is a prolifi c seed producer with production ranging from 25 to 5,000 seeds per plant. Biological. No biological control agents or pathogens are available for this weed.

19 FIELD BINDWEED (Convolvulus arvensis L.)

State Noxious Weed List: No. Field bindweed (creeping jenny) is a member of the morning glory family and is well-adapted to the North Dakota climate and environment. Field bindweed is a native of Europe and western Asia and was introduced to this country during colonial days when it was referred to as devilgut. Field bindweed primarily is a problem in the dryland farming areas of the Great Plains and Western states. Field bindweed is found in both cropland and pasture and rangeland in North Dakota.

Identifi cation and growth form: Field bindweed is a long-lived perennial that produces a dense ground cover. Th e twining stems vary from 1.5 to 6 feet or more in length. Leaf size and shape are variable, but generally the leaves are 1 to 2 inches long, smooth and shaped like an arrowhead. Flowers are funnel-shaped, about 1 inch diameter and white or pink. Th e fl ower stalk has two small bracts located 0.5 to 2 inches below the fl ower. Th e bracts, along with leaf shape and smaller fl ower size, distinguish fi eld bindweed from hedge bindweed. Field bindweed also may be confused with wild buckwheat because of similarities in leaf shape and vining habit. However, wild buckwheat is an annual rather than a perennial and has a very small (about 1/8 inch diameter) greenish-white fl ower. Roots of established plants may extend 20 to 30 feet laterally and be excavated as deep as 30 feet below the surface. Buds along the root system can send up shoots that start new plants. Th e root system contains a large quantity of carbohydrates that provide energy for both above- and below-ground plant growth. Buds located all along the root can send up new shoots or establish a new patch when roots are cut and moved, such as from cultivation. Seeds of fi eld bindweed vary from dark to brownish gray and are about 1/8 inch long. Th e fruit is a small, round capsule that contains up to four hard-coated seeds that can remain viable for at least 50 years. Field bindweed produces numerous seed in growing seasons with high temperatures and low rainfall and humidity. Field bindweed can be spread by seed, root fragments carried by farm implements, infested soil adhering to the roots of nursery stock, root growth from infested areas and by animals. 20 FIELD BINDWEED

Why is this plant a concern? make harvesting diffi cult by clogging machinery. Dense Field bindweed has a deep root system that competes fi eld bindweed infestations may reduce crop yields by 50 with crop plants for water and nutrients. Vines climb on percent to 60 percent. Land infested with fi eld bindweed is plants and shade crops, cause lodging of small grains and reduced in value.

How do I control this plant? Established fi eld bindweed is diffi cult to control. heat stress usually have smaller leaves with a thicker An eff ective control program should prevent seed cuticle and slower biological processes than plants production, kill roots and root buds, and prevent growing in more favorable conditions. As plant infestation by seedlings. Th is plant is very persistent stress increases, herbicide uptake and translocation and a successful control program must be more decreases, which in turn decreases herbicide persistent. performance. Th is is the reason why fi eld bindweed is harder to control in the more semiarid area of central Th e best control of fi eld bindweed is obtained with a and western North Dakota than in the eastern region. combination of cultivation, selective herbicides, and competitive crops or forage grasses. Cultural. Intensive cultivation controls newly emerged seedlings, may kill young fi eld bindweed Chemical. Long-term control of fi eld bindweed infestations and contributes to control of established from herbicides depends on movement of a suffi cient stands. Timely cultivations deplete the root reserves amount of herbicide through the root system to of established plants and stimulate dormant seeds to kill the roots and root buds. Th is requires use of germinate. systemic (movement throughout the plant) herbicides. Examples of herbicides that will reduce fi eld bindweed Intensive cultivation alone is not practical because infestations are products that contain dicamba crops cannot be grown during the tillage period, and (various), Paramount (quinclorac), Tordon (picloram) repeated tillage exposes the soil to erosion. However, and glyphosate (various). applying herbicides in combination with cultivation has been successful in reducing both fi eld bindweed Successful control of fi eld bindweed requires a long- infestations and the number of tillage operations. term management program. A herbicide applied once never will eliminate established stands; rather, Biological. Two non-native insects have been several re-treatments are required to control fi eld released to control fi eld bindweed with very minimal bindweed and keep it suppressed. Because of long seed success. Th e bindweed gall mite (Aceria malherbae) viability and tremendous food reserves stored in the is microscopic in size and feeding by nymphs causes roots, repeated chemical and/or mechanical control galling of fi eld bindweed stems. Th e larvae of the measures must be used. bindweed moth (Tyta luctuosa) feed at night on fi eld bindweed fl owers and leaves. Several native insects Herbicides should be applied when fi eld bindweed occasionally feed on this weed but damage to the is growing actively and stems are at least 12 inches plant has not been long-lived. No insect has been long. Herbicide performance can vary greatly due to released to feed on fi eld bindweed roots, which would environmental conditions in which the plants have be the most likely method of success in controlling been exposed. Plants growing under moisture or this weed.

21 HALOGETON [Halogeton glomeratus (M. Bieb.) C. A. Mey.]

22 HALOGETON

State Noxious Weed List: No. Why is this plant a concern? Halogeton is a poisonous, noxious weed introduced from Halogeton contains soluble sodium oxalates that are Eurasia and fi rst was reported in Nevada in 1934. Since poisonous to sheep and cattle. Th e plant is not palatable then it has spread to millions of acres in the western U.S., when green but may be consumed in toxic quantities in especially in range and wildlands. Th is plant oft en is found late summer, fall and winter. Dried plants may contain 30 in alkaline soils and semiarid regions, particularly when to 40 percent sodium oxalate, and the lethal dose for an the areas have been disturbed by overgrazing, off -road adult sheep is reached when the animal consumes 0.3 to vehicles, new roads and similar disturbances. Halogeton 0.5 percent of total body weight in a short time. Cattle are was reported in North Dakota for the fi rst time in 2009, not likely to eat enough to be poisoned unless feed is short. but because of the size of the infestations, it likely has been Sheep can develop a tolerance to halogeton through time in the state for some time. and consume this weed without illness if foliage from other plants is also part of the diet. Identifi cation and growth form: Halogeton is an annual weed in the goosefoot family and grows from a only a few inches to more than 24 inches tall, How do I control this plant? depending on location and moisture. Each plant has about Chemical. 2,4-D will control plants if applied fi ve main stems that grow out and then up from the crown, very early in the spring prior to fl owering. branching out similarly to Russian thistle, which this plant Escort (metsulfuron) is very eff ective and can resembles. Th e blue-green leaves are small and sausage- be applied throughout the growing season. shaped, and have a short bristle or spine at the end. Th e Plateau (imazapic) also will control this fl owers are found in the leaf axils, greenish and not showey. weed and can be applied both pre- and post- Even though the plant is an annual, the taproot can grow emergence. Spike (tebuthiuron) provides total nearly 2 feet down and out from the crown. Mature plants vegetation control for several years and may be have red stems. Th e brown-black seeds are contained in desirable for use on railroad ballast and oil fi eld a bracted pouch that oft en are mistaken for fl owers and locations, where halogeton oft en is found. give the plant a “wooly” appearance at maturity. Halogeton produces as many as 75 seeds per inch of stem and seeds Cultural. Halogeton is an early invader of are viable from one year (early season production) to more disturbed sites. Avoid overgrazing an area and than 10 years (developed aft er mid-August). reseed disturbed sites to native grasses and forbs to prevent halogeton from becoming established. Halogeton competes poorly with established perennial vegetation. Biological. No biological control agents or pathogens are available for this weed.

23 HOARY CRESS [Cardaria draba (L.) Desv.]

24 HOARY CRESS

State Noxious Weed List: No. Why is this plant a concern? Hoary cress (also called whitetop) is native to the Balkan Hoary cress is an aggressive plant that can form dense Peninsula, Armenia, Turkey, Israel, Syria, Iraq and Iran. monocultures on disturbed land. Disturbances such as Th e plant is widely introduced and naturalized throughout grazing, cultivation and especially irrigation can promote Europe and all other continents. Hoary cress fi rst was the colonization and spread of the plant. Hoary cress can introduced to the United States at Long Island, N.Y., in displace native plant species, thereby reducing biodiversity 1862 through a ship’s ballast or contaminated seed. and forage production. Whitetop contains glucosinolates that can be toxic to cattle but livestock only graze hoary cress in the spring if more palatable forage is not available. Identifi cation and growth form: Hoary cress is a deep-rooted perennial forb that can grow up to 2 feet tall. Stems of the plant are erect, branching above, glabrous or slightly to densely pubescent below, How do I control this plant? and appear gray. Hoary cress has both basal and stem Chemical. Hoary cress is in the mustard leaves. Basal leaves have scattered to dense pubescence, family so herbicides commonly used to control are irregularly toothed to entire and taper to a short stalk mustards generally work well on this weed. that attaches to the crown of the plant near the ground. Escort or Ally (metsulfuron), Oust or Telar Middle and upper stem leaves are sparsely pubescent, have (chlorsulfuron), MCPA and 2,4-D have been two lobes clasping the stem and are grayish green. Flowers used to control the plant. However, timing of of the plant are white, four-petaled and borne on slender herbicide application is important and should stalks. Seed capsules are shaped like an inverted heart and be done in early spring or in the fall aft er seed usually contain two seeds. Th e seeds are oval or round at germination. one end, narrow to a blunt point at the other and reddish- brown. Mechanical. Digging can provide control for small infestations of hoary cress if the entire Seedlings of hoary cress germinate in the fall and root system is removed. Hand-pulling generally overwinter as rosettes. Th e perennial root system is is not eff ective because the root system may not established the following spring and consists of vertical be entirely removed. Cultivation is the major and lateral roots. Both root types can produce adventitious factor for the spread of the plant because root buds that develop into rhizomes and new shoots. Plants fragments that are left behind can produce fl ower from May to June and begin producing seeds by new plants. Cultivation can eradicate plants if July. A single plant can produce between 1,200 and 4,800 cultivations are repeated frequently throughout seeds each year, with a single fl owering stem capable of the growing season for a period of two to four producing as many as 850 seeds. Seeds can remain viable years. in the soil for approximately three years. Biological. No biological control agents or pathogens are available for this weed.

25 HOUNDSTONGUE (Cynoglossum offi cinale L.)

26 HOUNDSTONGUE

State Noxious Weed List: No. state; however, animals will eat the dried plant in hay. Sheep are more resistant to the pyrrolizidine alkaloids than Houndstongue is a biennial poisonous herb that is native other livestock, while horses, especially when confi ned to to Eurasia. Th e plant is a member of the Borage family, small areas infested with houndstongue, are more likely which includes more commonly known plants such as to ingest toxic levels. Fatal liver disease in horses occurred Virginia Bluebells, Forget-Me-Nots and the fi ddlenecks. following two weeks of feeding hay with as little as 6 Houndstongue commonly is found in disturbed areas, percent houndstongue. including roadsides, trails, and in pasture and woodlands following soil disturbance or overgrazing.

Identifi cation and growth form: How do I control this plant? Houndstongue is a biennial that forms a rosette the fi rst Prevention is the best method to keep year of growth and bolts and fl owers the second season. houndstongue from invading North Dakota. Th e plant only reproduces from seed, but can spread Use only certifi ed weed seed-free hay and great distances because the barbs on the nutlets cling to eradicate new infestations before the plant can clothing, machinery and animals. Th e leaves are oblong, spread. very pubescent and rough, which resembles a hound’s Chemical. Escort (metsulfuron) is very tongue. Plants bolt during early summer, the second year eff ective for controlling houndstongue and can of growth, to a height of 1 to 4 feet and fl ower in mid-June. be applied throughout the growing season. Th e fl owers are small, arranged in clusters and not showy. First-year houndstongue rosettes are easily Flower color ranges from red to burgundy. Each fl ower controlled with 2,4-D applied from late May produces three to four nutlets, which are fl at and tear-drop to mid-June. Second-year plants are much less shaped with a very hard seed coat and numerous barbs. susceptible to 2,4-D. Plateau (imazapic) at high Plants generally are found along trails and roadsides, rates will control houndstongue both pre- and on the edge of wooded areas and in disturbed habitats. post-emergence, but grass injury, especially to Infestations oft en establish near areas where cattle and the cool season species is likely when Plateau is other livestock rub against something such as fence posts applied at the maximum rate. and trees or shrubs. Biological. A root weevil, Mogulones cruciger, has been released for control of houndstongue Why is this plant a concern? in Canada. Th e insect has become well- established in Alberta and has greatly reduced Houndstongue tends to be a nuisance weed rather than the houndstongue infestation in that province. a noxious plant unless infestations grow to become large However, this biological control agent has patches. Th e nutlets oft en become imbedded in the wool not been approved for release in the U.S. or hair of livestock, which can cause a loss of value of the Several other insects are being evaluated for wool and/or increase costs to remove the burs. Eye damage biological control of houndstongue, including can occur if burs become embedded in the eye or eyelids. a seed weevil (M. borraginis), a stem weevil Th e burs can be problematic for hikers, hunters and (M. trisignatus), a root beetle (Longitarsus fi shermen and also to their pets. quadriguttatus) and a root fl y (Cheilosia Houndstongue contains alkaloids that are especially toxic pasquorum); however, initial results are not to cattle and horses. Th e plant is rarely eaten in the green nearly as promising as those of the root weevil.

27 RUSSIAN KNAPWEED [Acroptilon repens (L.) DC.] syn. (Centaurea repens L.)

28 RUSSIAN KNAPWEED

State Noxious Weed List: Yes. Why is this plant a concern? Russian knapweed is the most widespread of the Russian knapweed can spread rapidly and is very knapweeds in North Dakota. It also is the only perennial of competitive with native species. Russian knapweed will the noxious knapweeds and is the most diffi cult to control. reduce forage production to near zero as the site oft en Russian knapweed oft en is found in poorly drained and becomes a monoculture. Russian knapweed also will infest saline/alkaline soils with supplemental water sources roadsides, pasture and rangeland and is the only knapweed such as rivers and streams. Th is persistent weed oft en is in the state that causes signifi cant losses in cropland. found in southwestern North Dakota, but increasingly infestations have been found statewide. Russian knapweed grows especially well in areas with supplemental water sources such as the Little Missouri and Heart rivers in How do I control this plant? North Dakota. Russian knapweed is one of the most diffi cult perennial weeds to control. If the plant is found Identifi cation and growth form: in cropland, then a combination of cultivation and herbicide treatments will suppress the Russian knapweed is a long-lived, deep-rooted perennial plant. However, herbicides at labeled rates with growth characteristics similar to Canada thistle. for cropland use will not control Russian Th e weed emerges in the spring from roots and grows to knapweed. 2 to 3 feet tall and is shrublike with spreading branches. Once established, Russian knapweed spreads mainly by Chemical. Tordon (picloram) is one of the underground root stocks as seed production is limited most eff ective herbicides used for Russian compared with other knapweed species. Th e leaves are knapweed control. Th e best control is obtained alternate and lobed lower on the plant while upper leaves when picloram is applied following several are entire. Flowering occurs from June to September and hard frosts (mid-October). Russian knapweed fl owers vary from light pink to lavender. Th e stems die plants may be dormant with gray stems and no back to the soil surface each year. leaves, but control the following spring is nearly 100 percent. Application in mid-September Two key characteristics distinguish Russian knapweed or during fl owering in midsummer provides from spotted and diff use knapweed. First, the fl owers shorter-term control than late applications. have rounded bracts with transparent tips that are quite Other herbicides used for Russian knapweed diff erent in appearance than the dark bracts of spotted and control include Escort (metsulfuron) and diff use knapweed. Second, the root of this perennial is dark Milestone (aminopyralid). brown to black, scaly as if the plant had been burned, and can grow to depths of greater than 20 feet. Th e fl owers of Cultural. Livestock generally will not graze Russian knapweed vary from light pink to lavender. Russian knapweed. Mowing and cultivation do not control this weed. Biological. Exploration and evaluation of biocontrol agents for Russian knapweed are in progress.

29 SPOTTED and DIFFUSE KNAPWEED [Centaurea stoebe spp. micranthos (Gugler) Hyek] and (C. diff usa Lam.)

Diffuse knapweed fl ower with spiny bracts

Spotted and diffuse knapweed

Spotted knapweed fl ower with black bracts

30 SPOTTED and DIFFUSE KNAPWEED

State Noxious Weed List: Yes. Why is this plant a concern? (both species). Spotted and diff use knapweed are aggressive, introduced Th e knapweeds are one of the most rapidly spreading weed species that rapidly invade pasture, rangeland and invasive species in the western U.S. Knapweeds already fallow land and cause a serious decline in forage and crop infest more acreage than leafy spurge in Montana and production. Spotted knapweed has few natural enemies Minnesota, and have been found in more than 25 counties and is not preferred by livestock as forage. Knapweed in North Dakota. Knapweeds are related to thistles and can infestations in North Dakota largely can be traced to seed spread even faster. For instance, spotted knapweed infested or hay brought in from neighboring states. Researchers approximately 25 acres in eight North Dakota counties in Montana have observed that spotted knapweed may in 1984 and had spread to more than 1,000 acres in 14 remain in a confi ned location for several years and then counties by 1997. Aggressive control programs have kept spread rapidly to adjacent areas. Controlling spotted and the infestation at approximately 1,200 acres since then, but diff use knapweed plants when they are fi rst observed more than half the counties in the state now have spotted and monitoring the site for several years to prevent knapweed infestations. Diff use knapweed can spread as reinfestation from seed are important quickly as spotted knapweed but has been kept in check in North Dakota and infests less than 300 acres. How do I control these plants? Identifi cation and growth form: Chemical and Cultural. Spotted and diff use Both are short-lived perennials or sometimes biennial knapweed confi ned to small, well-defi ned areas plants reproducing solely by seed. Seed remains viable should be pulled by hand or treated with a in the soil fi ve years or more, so infestations may occur herbicide as soon as detected to avoid spread a number of years aft er vegetative plants have been of the weed. First, all visible knapweed plants eliminated. Th e seeds can germinate from spring through should be removed and destroyed by burning early fall. Seedlings emerging in the fall oft en overwinter or mulching. Th en the areas should be treated as a rosette of leaves, resuming growth again in the spring. with a herbicide to prevent reinfestation from Th e plants grow 2 to 4 feet tall with one or more stems. Th e seedlings. Th e most eff ective herbicides for leaves are pale green and 3 to 4 inches long. Rosette leaves spotted and diff use knapweed control include are deeply lobed. Th e physical appearance of these two Milestone (aminopyralid ), Tordon (picloram) knapweed species is similar, except diff use knapweed is and dicamba (various). Treat an extra 10 to 15 generally shorter and more highly branched. Plants fl ower feet around the knapweed patches to control from early July through August and produce 1,000 or more seedlings. A careful follow-up program is seeds per plant. necessary to control missed plants and seedlings. Many attempts to control knapweed have failed Th ese species are distinguished by the bracts below the because follow-up treatments were not applied. fl ower. Spotted knapweed has stiff , black-tipped bracts while diff use knapweed has a rigid terminal spine about Biological. In general, the knapweed one-third of an inch long with four to fi ve pairs of shorter, infestations are small enough that herbicide lateral spines (crablike). If the plant is not fl owering, search and hand removal are the best and most cost- for last season’s fl ower stalk and identify the plant based eff ective treatments in North Dakota. Biological on the fl ower bracts. Both species have pink to light purple control agents have been introduced in and occasionally white fl owers. neighboring states to control spotted knapweed with limited success.

31 KOCHIA (Kochia scoparia L.)

32 KOCHIA

State Noxious Weed List: No. Why is this plant a concern? Kochia, also referred to as fi reweed, summer-cypress or Although kochia has been grown as a drought-resistant Mexican fi rebush, is a member of the Chenopodiaceae forage and may have reclamation value on disturbed or goosefoot family. Kochia is native to Eurasia and was land, the plant is a serious cropland weed. Kochia is an introduced to the United States in the early 1900s as an exceptionally competitive weed and a few uncontrolled ornamental. Kochia is palatable to livestock and has good plants can cause severe yield losses. Kochia is highly forage quality when grazed early in the season. Kochia adaptable and can be found on pasture, rangeland, road sometimes is referred to as tumbleweed. sides, ditch banks, wastelands and cultivated fi elds. Kochia can contain high nitrate levels and is toxic if Identifi cation and growth: overgrazed. Nitrate poisoning in livestock causes bloat and photosensitization. Toxic substances identifi ed within the Kochia is a taprooted annual forb that typically grows from plant include saponins, alkaloids, nitrates and oxalates. 1 to 6 feet tall. Stems of the plant are erect and spreading, Kochia is a main contributor to fall hay fever suff erers. much branched from the base and usually soft -hairy, but occasionally smooth. Stems are usually yellowish-green to green and oft en turn red with maturity. Leaves of the plant are alternate, lance-shaped and 0.5 to 2 inches long and How do I control this plant? have fringed hairs on the margins. Th e upper surface of the leaf is usually smooth and the lower surface usually is Chemical. Kochia has become resistant covered with soft hairs. Kochia fl owers are inconspicuous to several commonly used herbicides. ALS and greenish and form short, dense, terminal, bracted herbicides provide good kochia control unless spikes. Flowering generally occurs from July to September. resistant populations are present. Tank-mixing ALS herbicides with other broadleaf herbicides Kochia reproduces only by seed with more than 14,000 with diff ering modes of action is required to seeds produced per plant. Seeds are oval or egg shaped, reduce the risk of resistant kochia becoming dull brown, slightly ribbed and dispersed in the fall when established. Starane (fl uoxypyr) provides the plant becomes a tumbleweed. Seeds germinate in the excellent control of ALS-, triazine- and spring and have little or no seedbank viability and either dicamba-resistant kochia. Dicamba plus MCPA germinate or decay in one year. or bromoxynil plus MCPA will control small kochia plants. In many fi elds, 2,4-D and MCPA no longer control kochia due to repeated use and near eradication of susceptible kochia biotypes. Mechanical. Early tillage in the spring provides good control when conducted during the seedling stage of the plant. Mowing kochia prior to fl owering reduces seed production but may not kill the plant. Biological. No biological agents or pathogens are available for this weed.

33 LEAFY SPURGE (Euphorbia esula L.)

State Noxious Weed List: Yes. Leafy spurge was once the most diffi cult noxious weed to control in North Dakota and infests all 53 counties. Scientists at the North Dakota Agricultural College (NDAC) recognized leafy spurge could be a problem soon aft er it was fi rst identifi ed in the state, growing along a Fargo street in 1909. However, the plant was not added to the state noxious weed list until 1935, when leafy spurge was found growing in all but 10 counties. Th e largest single infestation at that time was estimated to be 193 acres in Foster County.

Latex is found in all True fl ower plant parts

Leafy spurge gall

Aphthona lacertosa Aphthona nigriscutis 34 LEAFY SPURGE

Despite several control programs led by the State Leafy spurge seeds may germinate to re-establish Agriculture Department and the Agriculture Extension infestations where total control of leafy spurge tops and Service, leafy spurge doubled in acreage every 10 roots has been achieved. Th e peak period of germination years, reaching nearly 1.8 million acres in the 1980s. A is late May and early June, but seeds can germinate and coordinated integrated program of biological, chemical seedlings become established throughout the growing and cultural methods directly led to the fi rst-ever reports season. Leafy spurge seedlings have a remarkable capacity of a decline in leafy spurge infestation in the state in the for vegetative reproduction and can reproduce vegetatively 1990s. within seven to 10 days aft er emergence. Seedlings typically do not fl ower during the fi rst year. Identifi cation and growth form: Th e root system of leafy spurge is extensive and consists of numerous coarse and fi ne roots that occupy a large Leafy spurge is a long-lived perennial that normally grows volume of soil. Roots are most abundant in the upper foot 2 to 3 feet tall from a woody crown from below the soil of soil, but some roots can extend to a depth of 15 feet or surface. Each crown area produces several upright stems, more. Th e roots are woody and durable in structure, with giving the plant a clumplike appearance. Th e plant bears numerous buds capable of producing new shoots. Th e numerous linear-shaped leaves with smooth margins. Th e root system contains a large nutrient reserve capable of leaves have a characteristic bluish-green color but turn sustaining the plant for years. yellow or reddish orange in the fall. Stems originating from crown buds and roots begin growth in late April, making leafy spurge one of the fi rst plants to emerge in the spring. Why is this plant a concern? Th e early and rapid growth gives leafy spurge a competitive Leafy spurge infestations may have more than 200 stems advantage over crop and pasture plants. All parts of the per square yard in sandy soil and even higher densities plant contain a milky juice called latex, which is a useful in heavy clay soil. Patches of leafy spurge usually spread identifying characteristic. vegetatively from 1 to 3 feet per year and form dense stands Leafy spurge produces a fl at-topped cluster of yellowish- that crowd out other plants by shading and competing for green petal-like structures called bracts, which surround moisture and nutrients. Forage production may be reduced the true fl owers. Th e showy, yellow bracts appear in late to 20 percent or less and most native plants are eliminated May and early June, giving the plant the appearance of because they cannot out-compete this weed. “blooming.” However, the true fl owers, which are small Leafy spurge contains a toxic substance that, when and green, do not develop until mid-June. Spring-applied consumed by livestock, is an irritant, emetic and purgative. herbicides are more eff ective on plants with developing It causes scours and weakness in cattle and may result true fl ower parts than on plants with developed bracts but in death. Th e toxin has produced infl ammation and loss undeveloped fl owers. of hair on the feet of horses from freshly mowed stubble Seeds are borne in pods, which contain three gray-brown, during haying and has caused mortality of sheep that oblong, smooth seeds. Aft er the seed has matured, the seed grazed leafy spurge exclusively. However, sheep and goats pods burst explosively and throw seeds up to 15 feet from will graze leafy spurge as a portion of their diet and can be the parent plant. An average of 140 seeds is produced per used as a form of cultural control. Animals will eat dried stem, and seeds may remain viable in the soil at least eight plants in hay, but many livestock, particularly cattle, avoid years. eating live plants

35 LEAFY SPURGE

How do I control this plant? Leafy spurge control must be considered a long-term management program. Generally, less than 6 inches of Aphthona larvae Longhorned beetle the root system is destroyed regardless if the control larvae method is biological, chemical or cultural. Research at North Dakota State University has shown that more of the root system is killed when a combination of control methods are used, compared with any method used alone. Chemical. Proper timing of herbicide applications is essential for good leafy spurge control. Leafy spurge is most susceptible to dicamba (Banvel and other trade Leafy spurge names), Paramount (quinclorac) or Tordon (picloram) hawkmoth applied either when the true fl owers and seeds are developing in June or aft er the stems have developed new fall regrowth in early to mid-September. Plateau (imazapic), fall-applied, provides better long-term but will reduce the infestation, slow the spread of the control and less grass injury than spring or summer weed and allow grasses to be grazed by cattle and horses. treatments. Combinations of Tordon plus Plateau or Grazing should be started early in the spring when the Tordon plus Plateau plus 2,4-D applied in June provide plant fi rst emerges. On large infestations, pastures should improved leafy spurge control compared with Tordon be divided so animals can be rotated regularly and the plus 2,4-D or Plateau applied alone in June. Th e Tordon entire infestation grazed in a timely manner. plus Plateau combination is not recommended for use in Sheep and goats are best suited to control leafy spurge on the fall. large infestations or along waterways and tree areas where Th e combination of Tordon plus Overdrive also will chemical control is restricted or cost is prohibitive and/ improve leafy spurge control compared with Tordon used or where success with biological control agents has been alone. Overdrive contains dicamba plus difl uenzopyr, minimal. which is an anti-auxin compound that oft en improves Leafy spurge provides good forage value and compares broadleaf weed control when applied with auxinlike favorably with widely used regional forages such as alfalfa herbicides such as Tordon, dicamba and 2,4-D. (Medicago sativa L.), smooth brome (Bromus inermis Glyphosate (various) applied for leafy spurge control has Leyss.) and crested wheatgrass (Agropyron desertorum a diff erent optimum application timing than the auxin Fischer ex Link). Before moving animals to a leafy spurge- herbicides (2,4-D, dicamba, picloram and quinclorac) free area, they should be contained for three to fi ve days or Plateau. Glyphosate is most eff ective for leafy so viable seed can pass through the digestive system. spurge control when applied either aft er seed fi lling in Biological. Biological control of leafy spurge was midsummer or aft er fall regrowth has begun but before initiated in the mid-1980s. To date, 10 species of insects a killing frost. Glyphosate alone applied during spring have been released in North Dakota for control of leafy growth stages generally provides poor long-term control. spurge, and six have become established. Four of the six Grazing. Sheep and goats provide an alternative for established insects are fl ea beetles (Aphthona spp.), which controlling leafy spurge top growth in pasture and have reduced the leafy spurge density more than any other rangeland. Grazing alone will not eradicate leafy spurge agent.

36 LEAFY SPURGE

Th e fi rst fl ea beetle released in North Dakota was Dakota in the 1980s, but to date, the population never has Aphthona fl ava Guill in 1986. Th is fl ea beetle has increased to suffi cient numbers to decrease leafy spurge. established at only a few sites in the state and occurs Th e spurge hawkmoth (Hyles euphorbiae L.), a foliar at densities too low to be eff ective. In 1988, a mixed feeder, was introduced in the 1970s but generally has not population of Aphthona czwalinae Weise and Aphthona survived and when it did survive, control was too late in lacertosa Rosenhauer were released near Valley City, the growing season to be very useful. N.D. By 1995, the majority (greater than 90 percent) of Limitations to biological control. Although fl ea beetles this mixed population was A. lacertosa. Two additional have become established throughout North Dakota, they fl ea beetles, Aphthona cyparissiae Koch and Aphthona have not been successful in all environments. To date, nigriscutis Foudras, were released the following year. A. approximately 30 percent of the releases have established lacertosa and A. nigriscutis were established in almost and the leafy spurge stem density has been reduced. every county in North Dakota by 1996 and have become In another 30 percent of the releases, the insects have the major biocontrol agents used for leafy spurge become established but the population density is too low control. to be eff ective. In the remaining releases, fl ea beetles have Although Aphthona spp. adults feed on leafy spurge not established. foliage, the major damage to the plant occurs when Cultural. Cultural control of leafy spurge includes the larvae feed on the roots. Larvae feed on both the properly timed cultivation and/or planting of competitive fi ne feeder roots used by the plant to absorb water and grass species. Cultural methods that only control leafy nutrients and the storage tissue of the root crown. Th is spurge top growth include mowing and fi re. All cultural feeding both destroys root tissue directly and causes control methods are more successful when combined the plant to be more susceptible to other methods of with herbicide treatments than when used alone. control, such as herbicides and infection from soil borne pathogens. Leafy spurge infestations must be controlled with herbicides such as glyphosate prior to seeding grass Research at North Dakota State University found fl ea species. Some perennial grass species that have competed beetle establishment was best on silt loam, silt clay loam, eff ectively to provide leafy spurge control include: clay loam and clay soils with an organic matter content Bozoisky Russian wildrye [Psathyrostachys juncea (Fisch.) of 6 percent to 9.5 percent. Flea beetles were least Nevski] and Luna pubescent wheatgrass [Elytrigia productive in fi ne sand to loamy fi ne sand soils with intermedia (Host) Beauv.], Rebound smooth brome an organic matter content of 1 percent to 3 percent. In (Bromus inermis Leyss.) and Rodan western wheatgrass addition, the release area needs to be well-drained and (Pascopyrum smithii Rydb.). Th ey are examples of grass not subject to frequent prolonged fl ooding or standing species that can compete relatively well with leafy spurge. water, which will kill the larvae. Generally, fl ea beetles Not only were the grasses very competitive with leafy have not been very successful in controlling leafy spurge spurge, but they also provided high yields and good growing along waterways, in shaded areas or in very nutritive value for grazing. Grazing following grass sandy soil. establishment should be limited and conducted at the Th e Spurgia esulae gall midge causes stem tip galls on proper growth stage of the grasses or leafy spurge will re- leafy spurge, thereby decreasing seed production. It infest the seeded area rapidly. has been most successful near wooded areas. However, Mowing and burning have been ineff ective for reducing a second control method was needed to reduce the leafy spurge infestations, but may result in uniform original leafy spurge infestation and to prevent spread regrowth that allows a more timely herbicide treatment. from roots. A stem-boring beetle, Oberea erythrocephala Also, mowing will reduce seed production if repeated Shrank, has been released and established in North every two to four weeks during the growing season.

37 COMMON MILKWEED and SHOWY MILKWEED (Asclepias syriaca L. and Asclepias speciosa Torr.)

Common milkweed fl ower

Monarch butterfl y larvae

Common milkweed

Showy milkweed fl ower

38 COMMON MILKWEED and SHOWY MILKWEED

State Noxious Weeds List: No. Why is this plant a concern? Common and showy milkweed are native to North Common milkweed can be aggressive in cropland areas America. Both species are robust, fl eshy perennial plants given the right conditions. Reasons for the increase in that fl ourish in orchards, waste places and along roadsides. milkweed densities in cropland include spread by the Milkweed has been used for medicinal, industrial, extensive root system, farmers using less tillage, several decorative and even for food purposes, despite having years of high rainfall and tolerance to most commonly some degree of toxicity. Milkweed is best known as a used herbicides. Given the opportunity to spread and primary food source for the monarch butterfl y. become established, common milkweed is extremely diffi cult to control. Identifi cation and growth form: As the common name implies, both species contain a thick, white, milky latex throughout the plant. Flowers are How do I control these plants? arranged in clusters at the top of the plant and are pink Since milkweed plants are native and a major to white. Common milkweed fl owers are held in tighter food source for the monarch and other clusters and are more pink than white compared with butterfl y species, control is discouraged. showy milkweed. Showy milkweed fl owers also have long However, if the plant becomes established in lobes that stand upright, which are not found on common cropland, crop yield loss may occur and control milkweed. Both species grow 2 to 4 feet tall and have large would be warranted. opposite leaves 3 to 5 inches wide and 6 to 10 inches long, which are covered with fi ne pubescence. Th ese perennial Chemical. Tordon (picloram) plus 2,4-D at plants have shallow fi brous roots. Milkweed grows over high rates will reduce milkweed density but a wide range of soil moisture conditions, but can become cannot be used in cropland. Glyphosate will dense under medium or high moisture levels. suppress milkweed temporarily in cropland while Express (tribenuron) can be applied with Seed pods are 3 to 5 inches long and contain dozens of fl at, 2,4-D plus dicamba for spot treatment. reddish-brown seeds with tuft s of hairs that allow the seed to travel long distances in the wind. An established market Cultural. Cultivation will reduce milkweed exists for milkweed seed fl oss as a nonallergenic fi ll to species in cropland but care must be taken not replace imported duck and goose down in comforters and to spread the roots to noninfested areas. for seed sales in prairie restorations and butterfl y gardens. Biological. Monarch butterfl y larvae feed Most commercial milkweed supplies still are collected heavily on milkweed and oft en remove a from the wild. majority of the leaves on a plant.

39 ORANGE HAWKWEED (Hieracium aurantiacum L.)

40 ORANGE HAWKWEED

State Noxious Weed List: No. Why is this plant a concern? Orange hawkweed is native to northern and central regions Orange hawkweed is an aggressive species that quickly of Europe. Th e plant fi rst was introduced in North America can develop into large, dense patches, thus reducing native in Vermont in 1875 as an ornamental. Orange hawkweed plant communities. Th e plant colonizes rapidly, forming escaped from landscape plantings, gardens and cemeteries a solid mat of rosettes. Orange hawkweed may have and now occurs throughout the eastern seaboard, into the allelopathic eff ects on neighboring plants. Midwest, extending west to Minnesota and Iowa and south to Virginia and North Carolina, and has been steadily spreading to the West. Orange hawkweed is described as the worst weed problem in the northern Minnesota How do I control this plant? Iron Range and has become a major weed problem in the Pacifi c Northwest. Chemical. Orange hawkweed can be controlled with Tordon (picloram), products that contain clopyralid (Curtail, Stinger, Identifi cation and growth form: Transline), Milestone (aminopyralid) or dicamba plus 2,4-D. Monitor infested areas for Orange hawkweed is a herbaceous perennial that contains several years to control new seedlings. a milky sap and commonly grows up to 12 inches tall. In the vegetative stage, the plant appears as a basal rosette Mechanical. Pulling or digging is not with many hairy leaves. Leaves are 4 to 6 inches long, dark recommended unless the infestation only green above, light green beneath, narrow and spatula- consists of a few plants because digging shaped. Each rosette is capable of producing 10 to 30 stimulates the growth of new plants from fl ower stems. Stems of the plant have short, stiff hairs and rhizomes, stolons and fragmented roots. may have one to three small, clasping leaves located below Biological. No biological control agents or the midpoint of the stem. pathogens are available for this weed. Orange hawkweed produces between fi ve and 30 red- orange fl ower heads that are 0.5 to 0.75 inch diameter. Flower heads are arranged in a fl at-topped cluster. Orange hawkweed seeds are tiny and black, and have a tawny tuft of bristles on the fl attened end. Th e plant spreads primarily vegetatively through runners (like strawberries) and rhizomes and to new sites by seed.

41 POISON IVY [Toxiodendron rydbergii (Small ex Rydb.) Greene]

42 POISON IVY

State Noxious Weed List: No. Why is this plant a concern? Poison ivy is a native species commonly found in wooded Th e “poison” in this plant is from a white oil called areas and in brushy areas, especially those along streams urushiol found in the phloem that causes an allergic or lakes. It can grow as a small shrub or vine and is found contact dermatitis in about 85 percent of the population. in North America from Canada to Mexico. Th e fi rst Plants retain urusiol even aft er desiccation and smoke published records of poison ivy in North America date from burning poison ivy can carry the oil. Th e reaction is back to the 1600s. A similar plant called poison oak (T. to the oil, not the plant itself, so one can react by touching diversiloba) is found only in states along the Pacifi c coast. objects that have come in contact with the plant, such as tools, and when removing footwear. Since it is an allergic reaction, people not sensitive to poison ivy can become Identifi cation and growth form: sensitized through time. Poison ivy is a perennial native small shrub that spreads by both rhizomes and seeds. Th e leaves are alternate with trifoliate leafl ets. Remember the rhyme: Leaves of three — let it be! Th e leaves are shiny green in the spring and How do I control this plant? turn yellow and deep red in the fall. Th e fl owers grow in Th e best control is avoidance, but if the plant axillary panicles, are yellow-green and not showy. Th e fruit is found close to walking trails, near a home is globed shaped, resembling small pumpkins, and turns or in your favorite fi shing area, herbicides yellow or light brown when mature. that contain triclopyr such as Garlon are very eff ective.

43 PURPLE LOOSESTRIFE (Lythrum salicaria L.)

State Noxious Weed List: Yes. Purple loosestrife, a beautiful garden plant with an aggressive nature, fi rst was introduced into North America in the early 1800s. Th e plant was sold in North Dakota by its genus name, Lythrum, for at least 50 years. Lythrum plants were brought to North Dakota for fl ower gardens because of their striking color, ease of growth, winter hardiness and lack of insect or disease problems. Th e garden varieties of purple loosestrife were sold by many cultivar names, including Morden Pink, Dropmore Purple and Morden Gleam. Th ese garden cultivars were thought to be sterile but now have been shown to cross-pollinate with the wild Lythrum type and sometimes with other Lythrum cultivars.

Identifi cation and growth form: Purple loosestrife is a rhizomatous perennial forb. Wild infestations are associated with moist or marshy sites. Th e stems are erect (1.5 to 8 or more feet tall) and four to six angled, and can be smooth or pubescent with few branches. Leaves are simple (0.75 to 4 inches long, 0.2 to 0.5 inch wide), entire, and can be opposite or whorled. Th e most identifi able characteristic of purple loosestrife is the striking rose to purple fl owers. Th e fl owers are

Galerucella spp. feeding on leaves

44 PURPLE LOOSESTRIFE How do I control this plant? Several methods are available for purple loosestrife control, including mechanical, biological and chemical. Th e size and location of a specifi c infestation will arranged on a spike, which can be a few inches determine the best control methods. In general, small to 3 feet long. Each fl ower has fi ve to seven petals infestations of a few plants can be controlled by digging, arising from a cylindrical green tube. Th e plant especially when plants are only a few years old. Larger usually fl owers from early July to mid-September infestations require treatment with herbicides and/or in North Dakota. Th e seed capsule is two-celled biological control agents. and contains many very small seeds (1 millimeter Chemical. Herbicides can be used to control purple long or less). Th e roots become thick and woody in loosestrife in areas too large to be controlled by digging. mature plants. Th e aerial shoots die in the fall and Also, herbicides can be applied to individual plants new shoots arise the following spring from buds at selectively in landscape situations to prevent killing the top of the root crown. Although the root crown desirable plants. Infestations growing along streams or expands and produces more shoots each year, the in marshy areas may require specialized equipment and maximum growth of the root crown diameter is application by trained professionals. limited to about 20 inches. Glyphosate (various trade names) will provide good Spread of purple loosestrife is primarily by seed, control of purple loosestrife when applied from July but the plant also can spread vegetatively from to early September. Many formulations of glyphosate stem cuttings. Research at NDSU has shown that are sold but only those labeled for aquatic use can be seed viability of purple loosestrife growing in applied in or near water. Garlon (triclopyr) is a selective North Dakota wetlands ranged from 50 percent broadleaf herbicide that will not kill cattail or other to 100 percent. With approximately 2.7 million desirable monocot species. Garlon will provide good seeds produced per plant, purple loosestrife has the to excellent purple loosestrife control when applied in potential to spread rapidly once established in an the pre- to early fl ower or late-fl ower growth stages but area. should not be used in landscapes or fl ower beds because soil residual of the herbicide may prevent establishment of other horticultural plants. Milestone (aminopyralid) and Why is this plant a concern? Milestone VM (aminopyralid plus triclopyer) can be used Th e most destructive impact of purple loosestrife in seasonally dry wetlands. invasions is on the ecology of aquatic sites. Purple Biological. Th ree biocontrol insect species fi rst were loosestrife forms dense monotypic stands as it released in North Dakota in 1997. Th ey are: displaces native wetland plants. Under optimum Galerucella pusilla — a leaf-feeding beetle conditions, a small, isolated group of purple Galerucella calmariensis — a leaf-feeding beetle loosestrife plants can spread to cover aquatic Hylobius transversovittatus — a root-mining weevil sites in just one growing season. When purple loosestrife replaces native vegetation, it also can Of these insects, the two Galerucella spp. leaf-feeding displace wildlife. Waterfowl, especially ducks, beetles have been most successful. Th ese insects avoid wetlands that have become dominated with overwinter as adults and lay eggs in early June in North Dakota. Th e adults and especially the larvae feed on the purple loosestrife. In addition, overall waterfowl leaves and fl owers of purple loosestrife. Following several production decreases as suitable nesting habitat summers of heavy feeding, purple loosestrife infestations is eliminated. Th e plant’s growth is generally too have been reduced greatly. However, since the largest compact to off er cover, and cover may be as crucial infestations in North Dakota are in urban areas, mosquito to wildlife as food. control programs have kept these insects from becoming well established.

45 SALTCEDAR (Tamarix spp.)

46 SALTCEDAR

State Noxious Weed List: Yes. choke waterways and even has dried up entire lakes. Native riparian species are quickly displaced by saltcedar, Saltcedar is the common name for several introduced which in turn causes displacement of native birds and species of shrubs or small trees, including Tamarix animals that generally do not feed on the leaves or eat the chinensis, T. parvifl ora and T. ramosissima. Saltcedar is saltcedar seeds. Saltcedar, even in the seedling stage, will native to Eurasia and fi rst was introduced into the U.S. to tolerate short-term fl ooding and can establish away from reclaim eroded areas and prevent further loss of stream waterways when seeds are washed in during fl ooding. banks, primarily in the southwest. Saltcedar has been Once established, the plants can become so thick cattle will sold in the horticultural industry, primarily for its wide not graze the area. adaptability and pink fl owers. Saltcedar became established in North Dakota as escapes from ornamental plantings or from seed fl oating along rivers. How do I control this plant? Identifi cation and growth form: Prevention is the best method to keep saltcedar Saltcedar is a shrubby bush or tree that can range in from invading North Dakota wetlands and size from 5 to 20 feet tall. Th e bark is a reddish brown, wildlands. Scouting along waterways and especially on younger branches. Th e leaves are small and removal of ornamental plantings have been fl at and resemble evergreen shrubs such as arborvitae. eff ective in reducing the spread of saltcedar in Flowers are pink to white and fi ve-petaled, and appear North Dakota. from mid to late summer. Th e seeds are extremely tiny and Chemical. Arsenal (imazapyr) is the most similar in size and color to pepper. Each seed has a pappus, widely used herbicide to control saltcedar. which allows it to fl oat long distances in water or move Arsenal also can be applied with a glyphosate in the wind. Seeds are short-lived and usually germinate formulation labeled for use in water. Do not within a few months aft er dispersal. remove saltcedar top growth for three years Once saltcedar seed germinates, it can grow rapidly to following herbicide application or resprouting a small fl owering shrub in one to two years. Th e plant will occur. Garlon (triclopyr) has been eff ective is deciduous and very hardy, and horticultural varieties when applied in the spring or late fall. are advertised to grow “in sun or shade, and in wet or Cultural. Control methods such as burning or dry areas” from USDA hardiness zones 2 to 7. Th e plant bulldozing have not been successful. quickly establishes a long, woody taproot to support a Biological. Th e leaf beetleDiorhabda elongata voracious thirst for water. Th e root system is capable of Brullé defoliates the leaves of saltcedar. Th is producing many new shoots if the top growth is removed insect feeds on the leaves of saltcedar and slowly by mechanical control methods or fi re. reduces plant vigor. However, it has not been consistently successful in reducing saltcedar Why is this plant a concern? infestations. Th is insect has not been released in North Dakota because of the small size of the Saltcedar can become a monoculture quickly along plants and low infestation level in the state. lakes and waterways. In the early morning and evening, moisture with high salt content is exuded from the foliage, causing the soil to become saline. Saltcedar can

47 ANNUAL AND SPINY SOWTHISTLE [Sonchus oleraceus L. and Sonchus asper (L.) Hill]

Spiny sowthistle

Annual sowthistle

48 ANNUAL AND SPINY SOWTHISTLE

State Noxious Weeds List: No. Why is this plant a concern? Th ese sowthistle species are from Europe and now are Th ese annual sowthistle species can become competitive established widely in the region. Th e plants oft en are in cropland, but otherwise are more nuisance species than mistaken for perennial sowthistle. However, perennial invasive. Because annual and spiny sowthistle oft en are sowthistle has a creeping perennial root system and larger found in waste areas and heavily used ground, such as and longer leaves, and grows 4 to 6 feet tall. Annual and parking lots and trails, they can be an indicator that land is spiny sowthistle oft en are found along roadsides and in being overgrazed or otherwise abused when these species waste areas, gardens and cultivated fi elds. start to appear in pasture and hay land.

Identifi cation and growth form: Annual and spiny sowthistle are both annuals and diff er How do I control these plants? primarily in leaf form. Spiny sowthistle, as the name Annual and perennial sowthistle species are not implies, has sharp, stiff prickles along the stem and leaves. true thistles and control options diff er between Leaves clasp the stem with rounded basal lobes (auricles) these weed families. that resemble a ram’s horn. Annual sowthistle leaves are deeply toothed lower on the plant but progressively Chemical. Products that contain metsulfuron less so on the upper stem and auricles are distinctly such as Escort or Ally are very eff ective in pointed. Both species have yellow fl owers, borne on a controlling sowthistle species. Commonly used long vaselike involucre, with several in a cluster. Annual herbicides for Canada thistle control such as and spiny sowthistle contain a milky latex and both grow Milestone (aminopyralid), Tordon (picloram) from a small taproot. Spiny sowthistle has slightly larger and dicamba (various) are less eff ective and fl ower heads (0.5 to 1 inch across) compared with annual require higher use rates. sowthistle (0.25 to 0.75 inch). Th e seeds for both are Cultural. Cultivation will control annual fl attened with three to fi ve ribs. Both species grow 2 to 4 sowthistle species in cropland. feet tall. Biological. No biological control agents or pathogens are available for these weeds.

49 PERENNIAL and MARSH SOWTHISTLE [Sonchus arvensis L. and Sonchus arvensis ssp. uliginosus (Bieb.) Nyman]

Marsh sowthistle fl ower

Perennial sowthistle

50 PERENNIAL and MARSH SOWTHISTLE

State Noxious Weed List: No. Why is this plant a concern? Perennial sowthistle was introduced from Europe and Perennial and marsh sowthistle can displace native plant placed on the state noxious weed list in 1935 when it communities by invading disturbed areas and undisturbed became a severe problem, especially in the northwestern natural habitats. Sowthistle can cause reduced crop yields, part of the state. Th e weed subsequently was removed from and lead to increased cultivation and herbicide costs. the list in 1999 aft er revised farming practices and new herbicides had severely reduced the infested acreage. Most sowthistle infestations in North Dakota are annual not perennial species. How do I control these plants? Annual and perennial sowthistle species are not Identifi cation and growth form: true thistles and control options diff er between these weed families. Marsh sowthistle is a subspecies of perennial sowthistle and thus the plants are very similar in form and growth Chemical. Products that contain metsulfuron habit. Both species have bright yellow fl owers similar such as Escort and Ally or Express (tribenuron) to dandelion, but perennial sowthistle fl ower bracts are are very eff ective in controlling perennial covered with gland-tipped hairs, while marsh sowthistle sowthistle species. Preharvest applications has smooth fl ower bracts. Both weeds have an extensive of glyphosate and products that contain creeping root system. Leaves are lobed below, but less so clopyralid or glufosinate will reduce perennial above and have prickles on the margin and are 4 to 10 sowthistle. Tordon (picloram) and Milestone inches long (longer than the annual species). Generally, (aminopyralid) will control sowthistle species perennial sowthistle has fewer but larger fl owers (1 to in noncropland. 1.5 inches across) than the annual species and end in a Cultural. Cultivation will reduce perennial terminal cluster. Some taxonomists consider marsh a sowthistle species in cropland but care must separate species from perennial sowthistle; others consider be taken not to spread the roots to noninfested it a subspecies. Both contain latex and grow from 1.5 to 6 areas. feet in height. Seeds are dark brown, with prominent ridges and have a tuft of white pappus or bristles. Biological. No biological control agents or pathogens are available for these weeds. Insects Sowthistle generally fl owers from July through September. can be observed on the fl ower heads of these Seed production is highly variable, but typically averages plants, especially perennial sowthistle, but they 30 seeds per fl ower head. Seed viability is relatively low for are feeding on sticky residue from the glands sowthistle and seeds usually do not survive longer than a on the fl ower bracts, which does not harm the year. plant. Perennial and marsh sowthistle can tolerate variable environments and can adapt well to wet areas with little soil disturbance. Th e plant commonly is found in cultivated areas, ditches, meadows, waste areas, sloughs, woods, lawns, roadsides, beaches, along rivers and lake shores. Sowthistle is adapted to many soil types, but seems to prefer low, fi ne-textured loam soils.

51 ST. JOHNSWORT (Hypericum perforatum L.)

State Noxious Weed List: No. St. Johnswort, also referred to as Klamath weed, is native to Europe, North Africa and parts of Asia and fi rst was introduced to the United States in the late 1600s for ornamental and medicinal purposes. St. Johnswort is sold as an antidepressant, oft en in the form of tea. However, St. Johnswort is also well-known to cause photosensitizing in man and animals. Numerous cultivated hybrids are available.

Identifi cation and growth form: St. Johnswort is a taprooted perennial herb that typically grows 1 to 5 feet tall. Stems are multi-branched, smooth, reddish and woody at the base. Th e leaves are opposite, entire, linear to oblong with in-rolled edges and 3/8 to 1 inch long. Th e leaves are dark green above and light green below and dotted with tiny, translucent glands. Th e “spotted leaf” appearance is a key characteristic for identifi cation.

St. Johnswort has opaque spots on the leaves

52 ST. JOHNSWORT

Flowers of the plant are yellow, starlike with fi ve petals and 0.5 to 1 inch in diameter, with tiny black dots on How do I control this plant? the margins. Petals are twice as long as the sepals and Chemical. A variety of herbicides can be numerous stamens arranged in three groups are apparent. applied for St. Johnswort control and are Th e seeds are egg-shaped and are held within a three- most eff ective when applied to seedlings and valved capsule that bursts at maturity. Seeds are tiny, dark young plants. Tordon (picloram) or glyphosate brown, 3/64 inch long, somewhat cylindrical, slightly (various) are most eff ective when applied in pointed at the ends and coarsely pitted. the spring. Escort (metsulfuron) also will St. Johnswort spreads both by underground and above- control St. Johnswort eff ectively. Herbicide ground creeping stems, and by seed. Annual seed treatments are most successful if applied at bud production ranges from 15,000 to 33,000 up to 100,000 stage before fl owering occurs and late in the with a small percentage germinating and reaching fall when the plant is going dormant. Repeated maturity. Seeds may remain viable in the soil for up to applications oft en are required to achieve 10 years. Germination occurs during the warm summer adequate management. months; however, seedlings may require several years Mechanical. Hand-pulling or digging may to reach reproductive maturity. Basal foliage that has be eff ective on small and isolated infestations overwintered may begin to bolt during early March and by if repeated several times per season and early April, older plants will have produced fl oral shoots. if conducted prior to fl owering and seed Flowering generally occurs from May through September production. In larger infestations, lateral roots and may be dependant on soil moisture. of older plants left behind can give rise to new plants. Why is this plant a concern? Biological. Several biological agents have been introduced into the United States for Glands found on the plant produce oils that contain St. Johnswort control since the mid-1940s. hypericin, a phototoxin. Once the plant is consumed, Th e Klamath weed beetle (Chrysolina animals become overly sensitive to sunlight, which results quadrigemina) was one of the fi rst highly in dermatitis, an infl ammation of the mucus membranes successful biological control insects introduced causing itching, swelling, blisters and open sores. All into North America. Th is insect is credited with growth stages of the plant are toxic, including dried plants controlling St. Johnswort on millions of acres in in hay. Poisoning or hypericism has been reported in cattle, California and the Pacifi c Northwest. horses, sheep and goats, with symptoms detectable within two to 21 days following ingestion of the plant. Light- However, the Klamath weed beetle has not haired or unpigmented skin areas such as the mouth, nose, been successful in all areas St. Johnswort ears and hooves are the most sensitive. occurs, so other agents have been introduced. Th e root-boring beetle Agrilus hyperici and the Livestock that suff er from hypericism generally lose leaf bud gall-forming midge Zeuxidiplosis giardi weight, are diffi cult to manage and possess reduced have become established but the eff ectiveness market value. Aff ected animals usually recover once has been quite variable. More recently, a St. consumption of St. Johnswort is stopped. St. Johnswort Johnswort foliage- and fl ower-feeding moth, has become popular as an herbal stimulant and will induce Aplocera plagiata, has been released and photosensitivity in some people. established in the northwestern United States.

53 BULL THISTLE [Cirsium vulgare (Savi) Tenore]

54 BULL THISTLE

State Noxious Weed List: No. Why is this plant a concern? Bull thistle is the least serious of the introduced thistles in Bull thistle occurs in all 48 contiguous states and most of North Dakota. Native Americans used bull thistle to treat Canada, but is designated noxious in only a few states. Bull hemorrhoids, which they likely learned from French fur thistle generally is found growing singularly or in small trappers. Bull thistle oft en is referred to as edible. Many patches in the northern and eastern counties of the state. plant parts from the root to the fl ower are eaten. Th e fl ower Th e large size and showy fl owers of the plant makes it petals are used as chewing gum. quite noticeable in pasture and rangeland, but it has little economic or ecological consequence. Identifi cation and growth form: Bull thistle is a biennial that grows from a fl at rosette of leaves the fi rst year to a flowering stem the second year, How do I control this plant? oft en 5 feet or more in height. Plants are multibranched; Bull thistle seldom reaches high enough stems have purple veins and are winged. Th e plant appears densities to warrant treatment. bushy rather than the candelabra appearance of plumeless or Canada thistle. A distinguishing characteristic of bull Chemical. Fall is the preferred time for thistle is the leaves. Leaf margins are deeply toothed applying herbicides for bull thistle control. and toothed again (double dentate) with prominent stiff Fall treatment allows more time for herbicide spines. Th e leaf surface has a distinct center vein with application than in the spring and thistle slight prickly hairs above and cottony pubescence below. control is generally best with fall treatments. Th e stems are very pubescent with dark purple veins. Th e Seedlings that emerge in summer aft er tillage rosettes of bull thistle are very pubescent with deeply lobed or previous herbicide applications will not bolt leaves and dark purple ribs. but remain in the rosette stage. Bull thistles are most susceptible to herbicides in the rosette Bull thistle fl ower heads usually are found singularly at form. the end of each stem branch. Th e fl owers are gumdrop shaped, large (2 to 3 inches tall), with long, stiff , yellow- Bull thistles can be controlled eff ectively tipped spines. Bull thistle fl owers from July to September, with Milestone (aminopyralid), clopyralid which is somewhat later than other thistles in the region. (Stinger, Transline or Curtai), Tordon Th e fl owers are generally purple but rarely a white form is (picloram), or dicamba (various) or dicamba observed. Achenes are 0.1 to 0.15 inch long, glossy light plus difl ufenzopyr (Overdrive). Products that brown to pale yellow or white with narrow dark brown contain metsulfuron (Escort, Cimarron Max, stripes and favored by birds. others) will control bull thistles in the spring and will eliminate seed production when applied in the bolting to bud growth stages. Cultural. Cultivation or hand-digging the rosette prior to bolting will kill the plant and prevent seed-set. Biological. No biological control agents or pathogens are available for this weed.

55 CANADA THISTLE (Cirsium arvense L.)

Female fl ower

Male fl ower

56 CANADA THISTLE

State Noxious Weed List: Yes. Canada thistle has an extensive underground root system that may penetrate the soil to a depth of 10 feet or more Canada thistle was introduced in North America as a seed and grow laterally 12 to 15 feet per year. Root buds occur contaminant in both French and British colonies. Th e fi rst randomly along the roots and initiate new shoots whenever legislation to control the weed was passed by Vermont in environmental conditions are favorable. Root segments 1795. Canada thistle has the dubious distinction of being one as small as 0.6 inch can initiate shoot growth and become of three weeds listed in 1885 by Dakota Territory as required established. Canada thistle is adapted to a wide range of of “every person” to be destroyed. Th e native distribution of soils, but it produces deeper roots in clay or muck soils than Canada thistle includes Europe, North Africa and central in sand, gravel or limestone soils. Asia. It also is found in China and Japan and has spread so extensively that it is diffi cult to distinguish the plant’s original Root bud development can occur nearly anytime during native range. Canada thistle is considered to be naturalized in the growing season, but is greatest when soil temperatures the northern Great Plains are warm, air temperatures are cool and the photoperiod shortens to 13 hours. Th ese conditions generally are found during the fall growing season. Th erefore, more Canada Identifi cation and growth form: thistle root-bud development occurs in the fall than any Canada thistle is a long-lived perennial that usually grows 2 other time of the year. Canada thistle grows best in the to 3 feet tall and bears alternate, dark green leaves that vary in northern regions of North America where temperature and size. Th e leaves are oblong, usually deeply cut, and have spiny, rainfall are moderate. Growth ceases when temperatures toothed edges. Canada thistle has small (3/4 inch diameter), exceed 85 degrees for extended periods. compact fl ower heads that appear on the upper stems. Canada thistle has been classifi ed into several varieties. Why is this plant a concern? Within these varieties are many ecotypes, which diff er Canada thistle has the potential to form dense infestations in growth characteristics, response to day length, and rapidly through vegetative reproduction, and the spread susceptibility to herbicides and cultivation. For example, leaf of these clones may continue indefi nitely, crowding out shape, head structure, and the number and size of spines and displacing native grasses and forbs through shading, can diff er with ecotypes. Canada thistle requires a 14- to 16- competition and possibly allelopathy. Canada thistle spread hour photoperiod to bolt and fl ower (April 19 to Aug. 22 in can change structure and species composition of natural North Dakota). Flower color can range from purple to light areas and reduce plant and animal diversity. Infestations lavender or even white. Stem color also can diff er from green of Canada thistle may contribute to the elimination of to lavender. endangered and/or endemic plant species. In wildlands, Flowering occurs from June to September. Male and female Canada thistle has the potential to increase fi re frequency fl owers are produced on diff erent plants, so cross-pollination and perhaps severity as a result of its abundant and readily is necessary for seed production. Flowers produce from 40 to ignited litter and fl ammable above-ground biomass. 80 seeds per head, which can move long distances, although Canada thistle can reduce yield of many crops severely. Yield most seed remain in the head until winter and eventually losses are directly proportional to the density and patchiness germinate nearby. of the infestation, with more than $40 million annually Th e smooth, light brown seeds (achenes) have a conical point lost in production in North Dakota alone. Wheat is a poor and are loosely attached to a tannish pappus at the tip, which competitor and Canada thistle infestations oft en increase aids in seed dispersal by wind. Seeds mature rapidly and are in a continuous-wheat farming program. Canada thistle able to germinate within eight to 10 days aft er pollination. also can be a severe problem in corn and soybean grown in Canada thistle overwinters in the rosette growth stage. rotation, with greater losses in soybean than corn.

57 CANADA THISTLE

How do I control this plant? Canada thistle is the only thistle in North Dakota that controlling dense infestations that require broadcast has become a cropland pest. Control strategies diff er application. Re-treatment will be necessary for several for Canada thistle in cropland compared with pasture, years to obtain long-term control. range and wildland. Cultural. Cropland. Canada thistle roots are much Chemical. Cropland. Th e best approach to Canada less winter hardy then many other perennial weeds thistle control in cropland should include an in-crop and timely cultivation actually can increase winter herbicide treatment to suppress Canada thistle growth, kill. Soil temperatures of 20 degrees or colder can minimize crop yield losses and prepare the thistle for a reduce Canada thistle regrowth from roots by more fall postharvest treatment. Preharvest and fall-applied than 50 percent. Following crop harvest, cultivate treatments provide the most eff ective long-term fi elds before the Canada thistle is 3 inches tall and control. Th e best herbicide to use will vary depending repeat before regrowth reaches 3 inches tall until on crop rotation. However, the control program freeze-up. Th is method has the combined advantage must be uninterrupted for two to three years if the of decreasing carbohydrate root reserves and the infestation is to be reduced. bare ground from the tillage will lead to colder soil temperatures, which increases winter-kill. Glyphosate (various trade names) can be used to control Canada thistle in glyphosate-resistant crops. An option for Canada thistle in row crops and fallow In-crop applications will not kill established thistle that includes both tillage and herbicides is known as stands. However, when used as part of an overall the rosette technique. Th e objective is to prevent the management program, glyphosate can reduce plants from bolting by using tillage and/or herbicide infestations. treatments until the day length is less than 15 hours, the photoperiod required for most Canada thistle Herbicides that can be used for Canada thistle growing plants to bolt. Th e thistles then will regrow as rosettes in small grains include 2,4-D, MCPA, dicamba only. Research at North Dakota State University has (various trade names), products that contain clopyralid found herbicide absorption and translocation to the (various trade names) and products that include roots of Canada thistle is greater when applied to tribinuron. Products containing clopyralid will control the rosette growth stage than when applied to bolted Canada thistle in fl ax, sugar beet and corn. Canada plants, making fall treatment of rosettes the most thistle may be suppressed in corn with products cost-eff ective method for long-term Canada thistle containing dicamba, while Basagran (bentazon) can be control. used in soybean. A second application is required 10 to 14 days aft er the fi rst for satisfactory suppression. Th e rosette technique for Canada thistle control in fallow includes the use of tillage and fall-applied Pasture, range and wildlands. Herbicides that control herbicides, while control in row crops includes in- Canada thistle in noncropland include products that crop herbicide treatments, tillage and fall-applied contain clopyralid (various), Tordon (picloram), herbicides. Periodic tillage in fallow is used to control dicamba (various) dicamba plus difl ufenzopyr Canada thistle shoots and other weeds until late July, (Overdrive), and Milestone (aminopyralid). Control when the day length is less than 15 hours. Herbicides is greatest when applied to Canada thistle at the early used for Canada thistle control, such as glyphosate bud growth stage (early summer) or in the fall to or clopyralid, then are applied to rosettes in late plants in the rosette form. Th ese herbicides applied at low rates may be the most cost-eff ective method for

58 CANADA THISTLE

September or early October. Research at NDSU has litura feeding by using additional control methods found that cultivation until late June prevented more such as mowing or applying herbicides. In addition, than 90 percent of Canada thistle from bolting in natural soil pathogens may become more destructive corn and soybean. due to multiple entry sites established by the insect. However, do not expect these insects alone to reduce Pasture, range, and wildlands. Repeated mowing will a Canada thistle infestation. reduce Canada thistle infestations. Mow whenever the plants are in the early bud growth stage to prevent A gall-producing fl y, Urophora cardui, causes seed-set. Several mowings a year are needed because meristematic galls but does little long-term damage plant populations vary in maturity. Mow as close to to the perennial thistle. Th e Canada thistle bud the surface as possible. If plants are cut above the weevil Larinus planus was an accidental introduction terminal bud before the stems elongate, they likely into North America. Th e insect feeds on developing will regrow. Mowing before the fl owers start showing fl owers to prevent seed production. Although L. color is important because plants mowed aft er that planus can survive under a wide range of climates, it likely will produce some viable seed. Mowing for has not reduced established Canada thistle stands. several years will reduce the root vitality of Canada Th e painted lady butterfl y (Vanessa cardui) can be thistle and will prevent seed production, reducing a very eff ective biological control agent but only the seed reserve. Mowing should be combined with a on an intermittent basis. Larvae of the butterfl y chemical control program for best results. feed on Canada thistle plants and can eliminate an Controlled burns oft en are used to help restore infestation. However, the insect generally is found wildlands to a more natural plant community. only in southern states such as Arizona and New Contrary to popular thought, research at North Mexico and will build up populations large enough to Dakota State University found that fall prescribed migrate north only once every eight to 11 years. Th e burns did not cause a long-term increase in Canada insect will migrate north as far as Canada and those thistle density; rather, Canada thistle emerged earlier fortunate enough to reside within the migratory in the burned compared with the nonburned areas. pathway will see a dramatic decrease in the Canada Th e eff ect was short-lived and Canada thistle densities thistle population. Unfortunately, the insect feeds were similar regardless of burn treatment the second on many plants, including crops such as soybean growing season aft er the burn. Also, no diff erences in and sunfl ower, and is not a candidate for long-term Canada thistle control occurred when herbicides were biological control of Canada thistle. used alone or combined with a prescribed burn. A native pathogen, Pseudomonas syringae pv. tagetis Biological. Two biological control agents have (Pst), causes the top of Canada thistle plants to turn been introduced for Canada thistle control, and a yellow to white. Th is pathogen may release a toxin third was introduced accidentally. To date, none have into the phloem of Canada thistle and kill the plant. been eff ective at reducing the weed on a large scale. Th e pathogen is most widespread during wet periods. Th e most widespread insect is Ceutorhynchus litura Attempts to produce this pathogen as a commercial weevil, which fi rst was released in North Dakota in biocide have not been successful. the 1970s. Th e larvae feed on the underground parts of Canada thistle for a short time but infestations generally are not reduced. One may take advantage of the early season stress on Canada thistle from C.

59 FLODMAN THISTLE [Cirsium fl odmanii (Rydb.) Arthur]

60 FLODMAN THISTLE

State Noxious Weed List: No. Why is this plant a concern? Flodman thistle is a native species found from Flodman thistle is more competitive than most other Saskatchewan and Manitoba to Iowa and Colorado. Th is native species and has the potential to infest large areas. thistle is a food source for a variety of insect and bird It is tolerant to high salt concentration in soil but not as species. Th e stems of Flodman thistle can be peeled and tolerant as Canada thistle. Although it grows best under eaten and were part of the Native American diet. moist conditions as most thistles do, it can survive under drought conditions, which gives it a competitive advantage on semiarid rangeland. Identifi cation and growth form: Flodman thistle is a deep-rooted perennial and usually grows 3 to 4 feet tall. Th e leaves are shiny green on top with slight pubescence and are white and very pubescent below, How do I control this plant? alternate, rigid and deeply lobed. Each lobe has three Native thistle species such as Flodman thistle points, one of which sticks out at nearly right angles, giving seldom become weedy because of the variety a fl ipping appearance, which is helpful to tell this plant of insects and birds that feed on the plant from the oft en similar appearing wavyleaf thistle. and several pathogens that cause a variety of Th e rosettes are oft en 4 to 6 inches in diameter with oblong diseases. However, of the native thistles found or lanceolate leaves that vary from deeply lobed to nearly in the region, Flodman thistle is one that can complete. Th e leaves are green to gray and especially form dense colonies, especially in dry years. pubescent below. Th e fl owers are deep purple to pink, Herbicides that are eff ective for controlling rarely white, tube shaped and approximately 1 inch long. Flodman thistle in noncropland include Th e fl ower heads have a strong yellow spine and a sticky products that contain clopyralid (various), secretion that attracts and catches insects. Flodman thistle Tordon (picloram), dicamba (various), usually fl owers from mid-July through September in North Overdrive (dicamba plus difl ufenzopyr) and Dakota. Th e achenes are about 0.1 to 0.15 inch long and Milestone (aminopyralid). Control is greatest oval, and vary from tan to brown and have a conspicuous when applied to thistle at the early bud growth yellow collar. stage (early summer) or in the fall to plants in the rosette form. Herbicide treatment will not be necessary if one allows the native pests to build in population and reduce this thistle through time. Flodman thistle has not been a problem weed in cropland.

61 MUSK THISTLE (Carduus nutans L.) State Noxious Weed List: Yes. Musk thistle is the most common biennial invasive thistle in North Dakota. Musk thistle is native in southern Europe and western Asia and was introduced into North America in the early 1900s. Two subspecies that diff er in fl ower size and pubescence occur in North Dakota.

Identifi cation and growth form: Musk thistle likely is the most easily identifi ed invasive thistle in North Dakota, yet many people confuse this plant with either bull thistle or plumeless thistle. Musk thistle oft en grows in excess of 6 feet tall, has very large fl owers that tend to droop, and the fl ower has very characteristic brown bracts that resemble a pine cone. Th e fl owers usually are deep rose, solitary and very large, ranging from 1.5 to 3 inches in diameter. Rosettes are dark green with a light green midrib, usually smooth and lacking pubescence and oft en grow 2 feet or more in diameter. Musk thistle stems are usually very branched with spiny wings; however, the wings are interrupted and not complete along the stem as with bull or plumeless thistle. Th e leaves are oblong to lanceolate and lobed with slender spines along the margin. Th ey generally have little pubescence underneath, which helps distinguish musk thistle from plumeless thistle. However, the subspecies C. nutans macrocephalus (Desf.) has very pubescent leaves. Musk thistle fl owers from July to late September. Th e average musk thistle plant produces in excess of 10,000 seeds per plant and, under favorable conditions, may produce 120,000 seeds per plant. Seed germination

62

MUSK THISTLE

averages 30 percent. Th e seed generally germinates in the Why is this plant a concern? summer and fall, and the plant overwinters as a rosette. Musk thistle tends to invade overgrazed or otherwise Th e following spring, the plant resumes vegetative growth, disturbed pastures, rangeland, roadsides and waste bolts and fl owers. Aft er setting seed, the plant dies, thereby areas. Movement into cropland is generally from nearby completing the life cycle. Occasionally biennial thistles noncropland or roadsides. Musk thistle spreads rapidly have winter annual, annual or short-lived perennial and can form very dense stands that crowd out desirable characteristics. forages and native species.

How do I control this plant? Biennial thistles do not survive under crop rotation Since biennial plants such as musk thistle reproduce since they cannot tolerate tillage or crop competition. only from seed, the key to a successful management Planting infested areas to any crop will eliminate program is to control the plants before fl owering. biennial thistles. Chemical. Fall is the preferred time for applying Biological. Th e seed weevil Rhinocyllus conicus was herbicides for biennial thistle control. Fall treatment introduced from Eurasia to control musk thistle by allows more time for herbicide application than in the reducing seed production. Larvae develop in the fl ower spring and thistle control is generally best with fall head and consume the seed as it develops. Th e weevils treatments. Seedlings that emerge in summer aft er can reduce seed production by nearly 80 percent, but tillage or previous herbicide applications will not bolt they are attracted more to earlier blooming rather but remain in the rosette stage. Biennial thistles are than to later blooming fl owers. Th e late-season fl owers most susceptible to herbicides in the rosette form. produce seeds with little damage from the weevil, which sustains the musk thistle population. Building Biennial thistles can be controlled eff ectively with a high enough population of insects to greatly reduce Milestone (aminopyralid), Stinger, Transline or seed production takes fi ve to 10 years. Th ese insects Curtail (clopyralid), Tordon (picloram), or dicamba fi rst were introduced into North Dakota in the early (various) or dicamba plus difl ufenzopyr (Overdrive). 1970s. R. conicus is not specifi c to musk thistle and Products that contain metsulfuron (Escort, Cimarron has been found feeding on other invasive thistles, Max, others) will control biennial thistles in the such as Canada thistle. However, this insect also feeds spring and will eliminate seed production when on native thistles, including several that are on the applied in the bolting to bud growth stages. protected or endangered species list. Cultural. Repeated mowing will reduce musk thistle Th e thistle crown weevil (Trichosirocalus horridus) was infestations. Mow whenever the plants are in the introduced into North America from Europe in the early bud growth stage to prevent seed-set. Several mid-1970s. Larvae of this insect feed on the growing mowings a year are needed because plant populations tip as the musk thistle rosette bolts. While seldom vary in maturity. Mow as close to the surface as eff ective by itself, it does help control musk thistle possible. Plants should be cut below the terminal bud when combined with Rhinocyllus conicus. Feeding by T. before the stem elongates or the weed will regrow. horridus larvae on musk thistle growing tips causes the Mowing before the fl owers start showing color is plant to produce multiple shoots. Th e resulting fl ower important because plants mowed aft er that likely heads are reduced in size and produce fewer seeds, will produce some viable seed. Mowing should be and the increased number of fl ower heads results in an combined with a chemical control program for best increased population of R. conicus. results.

63 PLUMELESS THISTLE (Carduus acanthoides L.)

64 PLUMELESS THISTLE

State Noxious Weed List: No. Why is this plant a concern? Plumeless thistle fi rst was introduced into North America Plumeless thistle can become very weedy and form dense in the 1870s along the East Coast as a contaminant in colonies, especially along waterways, ditches and roadsides ship ballast. Plumeless thistle is one of the most common in summers following wet falls. Plumeless thistle seldom invasive thistles in the mid-Atlantic and upper Midwestern is found in cultivated fi elds, even when infestations are states. Although found as far west as Washington state, it nearby in roadsides or pastures. Th e numerous spiny is less common than musk and bull thistle and is not listed branches make walking through infestations by people or on the North Dakota state noxious weed list. grazing by animals very diffi cult.

Identifi cation and growth form: Plumeless thistle is a winter annual or biennial and How do I control this plant? generally is found only in eastern North Dakota. Plumeless Chemical. Fall is the preferred time for thistle tends to be shorter than other noxious biennial applying herbicides for plumeless thistle thistles and generally reaches 1 to 4 feet tall. Th e stems are control. Fall treatment allows more time winged and very branched, giving the plant a candelabrum for herbicide application than in the spring appearance. Th e wings are very spiny and are continuous and thistle control is generally best with fall along the stem and not interrupted as musk thistle. Th e treatments. Seedlings that emerge in summer leaves are deeply lobed, narrower than musk thistle and aft er tillage or previous herbicide applications very pubescent underneath. Each lobe has one to three will not bolt but remain in the rosette stage. very sharp marginal spines. Flower heads are small (0.5 Plumeless thistles are most susceptible to to 1 inch) but very numerous and pink to purple or very herbicides in the rosette form. rarely white. Th e bracts are very narrow and resemble spines. Th e heads can be singular or in clusters of two Plumeless thistles can be controlled eff ectively to fi ve. Th e achenes are small, gray to light brown with a with Milestone (aminopyralid), Stinger, distinct, light apical collar and slightly curved. Transline or Curtail (clopyralid), Tordon (picloram), or dicamba (various) or dicamba Rosettes of plumeless thistle resemble musk thistle rosettes, plus difl ufenzopyr (Overdrive). Products that but are more deeply lobed and much more pubescent. contain metsulfuron (Escort, Cimarron Max, Plumeless thistle rosettes have wavy leaves with yellow others) will control biennial thistles in the spines along the white leaf margins and resemble holly. Th e spring and will eliminate seed production when plant bolts and fl owers in late April to early May. applied in the bolting to bud growth stages. Cultural. Repeated mowing will reduce plumeless thistle population but must be done prior to fl owering or viable seed will be produced. Plumeless thistle will not survive tillage operations used in cropland. Biological. Both Rhinocyllus conicus and Trichosirocalus horridus, which were released for musk thistle control, attack plumeless thistle.

65 SCOTCH THISTLE (Onopordum acannthium L.)

66 SCOTCH THISTLE

State Noxious Weed List: No. Why is this plant a concern? Scotch thistle is a native of Eurasia and has become Scotch thistle is an aggressive species that can out-compete naturalized in portions of western North America. Scotch and decrease desirable forage. Th e plant also can degrade thistle can thrive in well-drained, sandy or stony soils. Th e wildlife habitats and recreational areas. Scotch thistle plant occurs in pastures, croplands, rangelands, roadsides infestations can become impenetrable, thorny barriers that and construction sites but prefers disturbed areas and sites severely limit land use by wildlife, livestock and man. near ditches. Scotch thistle has regal stature. During the reign of Malcolm I of Scotland, Norsemen attempted to capture the Staines Castle by wading across the moat in their bare feet, only to fi nd the moat dry and overgrown How do I control this plant? with thistle. Th e painful cries by the warriors roused the castle guards and the Norsemen were defeated. To Scotch thistle reproduces solely through seed commemorate this victory, the fl ower became the emblem production. Seeds generally germinate in of Scotland. late fall but germination can occur anytime throughout the year. Chemical. Scotch thistle can be controlled Identifi cation and growth form: eff ectively with Milestone (aminopyralid), Scotch thistle is a biennial herb that can grow up to 12 feet Stinger, Transline or Curtail (clopyralid), tall. Stems of the plant are hairy or cottony, and have broad, Tordon (picloram), or dicamba (various) spiny wings. Leaves are large, spiny and covered with fi ne, or Overdrive (dicamba plus difl ufenzopyr). dense hairs that give Scotch thistle a grayish-green, cottony Products that contain metsulfuron (Escort, appearance. Upper leaves are alternate and have prominent Cimarron Max, others) will control biennial triangular lobes that occur on the margins. Lobes of the thistles in the spring and will eliminate seed leaf end with a prominent, sharp, green to white spines. production when applied in the bolting to bud growth stages. Flower heads are terminal, numerous and 1 to 2 inches in diameter. Flowers are pale purple to red and subtended Mechanical. Hand-pulling small infestations with a series of overlapping bracts tipped with a spine. of Scotch thistle can be an eff ective control Seeds are oblong to obovate, four-angled, deep brown to method. Mowing prior to seed dispersal black, about 3/16 of an inch long and wrinkled. Plants may limit the amount of seed available for can produce 70 to more than 300 fl ower heads that can germination. However, if the plant is cut aft er produce 100 to 200 seeds per head. Th erefore, a single fl owers begin to show color, viable seed may plant can produce 8,400 to 40,000 seeds. Seed viability can still be dispersed. range from one to more than16 years, depending on seed Biological. Research on biological control burial depth. agents for Scotch thistle is in progress. Lixus cardui Olivier (Coleoptera: Curculionidae), a weevil from Europe, fi rst was used by Australian researchers to control Scotch thistle. However, host-specifi city testing needs to be researched further to ensure that native thistles are not aff ected by the release of this agent in North America.

67 WAVYLEAF THISTLE [Cirsium undulatum (Nutt.) Spreng.]

68 WAVYLEAF THISTLE

State Noxious Weed List: No. Th e fl owers are most oft en pink or purple, but there is a Wavyleaf thistle is a native species and is common in white-fl owered form, f. album Farwell. Th e fl owers are western North Dakota. Various Native American tribes usually more than 2 inches in diameter, with globe-shaped used wavyleaf thistle to treat gonorrhea and syphilis. Th e heads. Th e yellow spines on the heads lack the sticky remedy involved drinking a tea made from the plant and secretion found on Flodman thistle. Th e achenes are brown then elevating the body temperature to induce sweating. without a lighter apical band or with only a very narrow A tea also was made from the roots to treat diabetes and lighter margin. stomachache. Th e roots were boiled and used in soup. Wavyleaf thistle is a larger plant than Flodman thistle. Generally Flodman thistle is more common than wavyleaf Identifi cation and growth form: in eastern North Dakota, but wavyleaf gradually becomes the predominant species in the central and western Wavyleaf thistle is a perennial native plant that oft en is portions of the state. confused with Flodman thistle. Wavyleaf thistle tends to fl ower from July to September, oft en a week or two earlier than Flodman thistle. Wavyleaf thistle tends to be Why is this plant a concern? more spiny and the leaves less deeply lobed than Flodman Generally wavyleaf thistle is kept in check by native insects thistle. Also, wavyleaf thistle is found in well-drained and birds that feed on the plant as well as native pathogens soils, generally in drier locations than those occupied by that reduce plant vigor and growth. Wavyleaf has become a Flodman thistle. Wavyleaf thistle grows 3 to 4 feet tall problem when the plant spreads beyond its normal range, and oft en is associated with sagebrush communities and such as the Pacifi c coast. Otherwise this plant does not rangeland but is less common in moist meadows. warrant control eff orts. Th e leaves of wavyleaf are alternate and tipped with yellow spines. Th e leaves are very pubescent, giving the plant a gray cast, and are less deeply lobed than Flodman thistle. Leaves are strongly undulated or wavy, which gives the plant its common name. Th e stem of wavyleaf thistle is very pubescent and generally thicker than Flodman thistle. Rosette leaves are also very wavy and gray in appearance.

69 DALMATIAN TOADFLAX and YELLOW TOADFLAX (Linaria genistifolia ssp. dalmatica (L.) Maire & Petitm. and Linaria vulgaris Mill.)

Dalmatian toadfl ax

Dalmatian toadfl ax has broad heart-shaped leaves

70 DALMATIAN TOADFLAX and YELLOW TOADFLAX

Yellow toadfl ax has narrow linnear leaves

Yellow toadfl ax fl owers have orange throats

Yellow toadfl ax

71 DALMATIAN TOADFLAX and YELLOW TOADFLAX

State Noxious Weed List: Identifi cation and growth form: Dalmatian toadfl ax: Yes. Dalmatian and yellow toadfl ax are members of the Yellow toadfl ax: Yes. snapdragon family and thus easily recognizable by the Both Dalmatian and yellow toadfl ax are escaped perennial bright yellow fl owers, which have swollen corolla tubes that ornamental plants that were introduced in the mid-1800s. fl are into two “lips” with an orange throat (yellow toadfl ax) Dalmatian toadfl ax is native to the Mediterranean region, and long spur. Th e fl owers are 1 to 1.5 inches long with specifi cally the Dalmatian Coast of Croatia, while yellow many fl owers on a raceme. Both species have an extensive toadfl ax is from Eurasia. Yellow toadfl ax fi rst was recorded creeping rhizomatous root system that spreads like leafy in North Dakota by H.L. Bolley from a collection made in spurge. Th e most distinctive diff erence between the species Fargo and described as “most abundant in Barnes County” is that Dalmatian toadfl ax has broad, heart-shaped leaves in the 1940s by O.A. Stevens. Th e fi rst record of Dalmatian that clasp a woody stem, whereas yellow toadfl ax has toadfl ax is from Walhalla in Pembina County in 1937 by narrow, linear leaves with a narrow stem. Stevens. Th e plants begin regrowth from the roots as soon as the Th e toadfl axes are most likely to be found along highways, soil warms in early spring. Toadfl ax fl owers from late railroad tracks and other transportation or communication June through August in North Dakota and single plants lines, or anywhere livestock is brought into the state. Oft en may produce more than 500,000 seeds that are dispersed the origins of an infested area can be traced back to an by wind, rain, wildlife, and movement of forage and escape from an ornamental planting. Dalmatian toadfl ax livestock. Th e seed is disk-shaped, 0.08 inch in diameter has been reported only as small patches in a few counties, and dark brown to black, and oft en have irregular papery generally in the western part of North Dakota. However, wings. Seed dispersal begins a few weeks aft er fl owering yellow toadfl ax has been found in many counties across the and continues into winter. Th e roots of a single plant can state and is on the verge of becoming a major problem for extend 10 feet and give rise to daughter plants every few land managers in North Dakota. inches.

Why are these plants a concern? Th e toadfl ax species are aggressive and will displace forage in pastureland and native species in wildland. Yellow toadfl ax can be mildly poisonous to livestock that graze it. Although the toadfl axes may be slow to establish, once plants take root, control is very diffi cult since most herbicides are ineff ective. Dalmatian toadfl ax seedlings are relatively poor competitors with grass species, but once established, the weed can become extremely invasive, especially on dryland sites, disturbed areas and roadsides. Yellow toadfl ax is adapted to more moist sites than Dalmatian toadfl ax and oft en is found in pasture, meadows and ditches.

72 DALMATIAN TOADFLAX and YELLOW TOADFLAX

How do I control these plants? Prevention is the best method to keep Dalmatian Cultural. Th e long-term use of proper stocking rates and yellow toadfl ax from invading North Dakota to maintain competitive forage species has helped pasture, rangeland and wildlands. Herbicides can reduce the spread of toadfl ax into grazing lands. be eff ective but require repeated treatments at high Burning is not eff ective because soil temperatures do rates. not get high enough to kill the roots. Burning even may have a detrimental eff ect and cause an increase Chemical. Tordon (picloram), Plateau (imazapic) in the number of stems due to reduced cover. and Telar (chlorsulfuron) will control Dalmatian toadfl ax when applied at maximum use rates Biological. Several insects have been introduced during fl owering or late fall. No herbicide is for toadfl ax control. eTh stem-boring weevil Mecinus labeled for yellow toadfl ax control, but research janthinus has been the most successful and can at North Dakota State University has found that a reduce Dalmatian toadfl ax stands relatively quickly. combination treatment of Tordon plus Overdrive M. janthinus larvae mine in Dalmatian toadfl ax (dicamba plus difl ufenzopyr) applied in late fall will stems, which slowly causes the plants to wilt and die. reduce yellow toadfl ax infestations for at least two Repeated attempts to establish M. janthinus on yellow years. See the latest edition of the “North Dakota toadfl ax in North Dakota have failed, likely because Weed Control Guide” for application rate and the larvae cannot survive in the much narrower timing recommendations. diameter stem of yellow compared with Dalmatian toadfl ax.

73 YELLOW STARTHISTLE (Centaurea solstitialis L.)

State Noxious Weed List: No. Yellow starthistle is an extremely invasive, fast-spreading member of the knapweed family and native of the Mediterranean region. Yellow starthistle fi rst was collected in North Dakota in Grand Forks County in 1964 and was added to the state noxious weed list in 1999 aft er plants were observed in several newly seeded CRP fi elds. Yellow starthistle infests more than 15 million acres

74 YELLOW STARTHISTLE

in California and has displaced leafy spurge as the most However, to present symptoms, such as the inability to eat invasive weed found in Idaho. Yellow starthistle presently or drink, stiff or trembling legs and a stiff , swollen, “frozen” has been found in the neighboring states of Montana, face, a horse must eat an amount nearly equivalent to its South Dakota and Minnesota. body weight.

Identifi cation and growth form: Yellow starthistle is an annual that oft en grows 3 feet or How do I control this plant? more tall and is branched with winged stems. Each stem Prevention is the best method to keep yellow terminates in bright yellow fl owers with needlelike straw- starthistle from invading North Dakota colored bracts oft en up to 2 inches long. Lower leaves are cropland, rangeland and wildlands. Yellow deeply lobed while upper leaves are entire. Both stems and starthistle is most likely to be found in recently leaves are covered with pubescent hairs that give the plant seeded pastures or CRP fi elds; along highways, a grayish appearance. Yellow starthistle reproduces (and railroad tracks and other transportation or thus spreads) only by seed. A single plant can produce as communication lines; or anywhere livestock many as 150,000 seeds, of which 90 percent or more are is brought into the state. Previous infestations viable and can remain dormant in the soil for a few years. in the state can be traced to contaminated Most yellow starthistle seeds are plumed and disperse grass seed, including those used in CRP and when mature. However, some seeds are plumeless and stay contaminated hay, and from movement of in the fl ower head until winter storms disperse them in out-of-state livestock and vehicles into North blowing snow. Yellow starthistle has a long tap root similar Dakota. to spotted knapweed or dandelion. Chemical. Th e most eff ective herbicides for Yellow starthistle seeds can germinate either in the fall yellow starthistle control include Milestone following cool rains and overwinter as a rosette or in the (aminopyralid), Tordon (picloram) and spring aft er snowmelt. Yellow starthistle begins to bolt in dicamba (various). Treat an extra 10 to 15 feet late May to early June. Flowering starts in early to mid- around the infestations to control seedlings. July, similar to Canada thistle. Yellow starthistle oft en can A careful follow-up program is necessary to go unnoticed until the plant begins to fl ower, but once control missed plants and seedlings. the bright yellow, dandelionlike fl owers bloom, the plant is easily detected. Flowering continues until mid to late Cultural. Grazing, mowing, burning, August, then the plant dries to a straw color, the seeds cultivation and maintaining competitive mature and the cycle repeats. forages can be used in conjunction with herbicides to keep yellow starthistle from establishing in North Dakota. Hand-pulling is Why is this plant a concern? also eff ective for control of this annual weed. Livestock and wildlife will not graze where yellow Biological. Biological control is in the starthistle grows because of the sharp spines around the research and implementation stage in states fl ower. Yellow starthistle is adapted to a wide variety of with large acreage of yellow starthistle such as environments and will out-compete most native plants California. However, biological control is not for nutrients and moisture, reducing both native wildlife recommended in North Dakota because of the and plant diversity. Yellow starthistle can cause “chewing limited yellow starthistle acreage. disease” in horses, which is a lethal neurological disorder.

75 The printing and design costs of this publication were paid for in part by the North Dakota Department of Agriculture and U.S. Forest Service. North Dakota State University does not discriminate on the basis of age, color, disability, gender expression/identity, genetic informa- tion, marital status, national origin, public assistance status, sex, sexual orientation, status as a U.S. veteran, race or religion. Direct inquiries to the Vice President for Equity, Diversity and Global Outreach, 205 Old Main, (701)231-7708. This publication will be made available in alternative formats for people with disabilities upon request, (701) 231-7881. The U.S. Department of Agriculture (USDA) prohibits discrimina- tion in all its programs and activities on the basis of race, color, national origin, age, disability, and where applicable, sex, marital status, familial status, parental status, religion, sexual orientation, genetic information, political beliefs, reprisal, or because all or part of an individual’s income is derived from any public assistance program. (Not all prohibited bases apply to all programs.) Persons with disabilities who require alternative means for communication of program information (Braille large print, audiotape, etc.) should contact USDA’s TARGET Center at (202) 720-2600 (voice and TDD). To file a complaint of discrimination, write to USDA, Director, Office Of Civil Rights, 1400 Independence Avenue, S.W., Wash- ington, D.C. 20250-9410, or call (800) 795-3272 (voice) or (202) 720-6382 (TDD). USDA is an equal opportunity provider and em- ployer. 5M-4-10, 2.25M-6-11, 6.5M-10-12