Because of this, beekeepers are interested in keeping patches of spotted knapweed near their hives. Spotted knapweed is a native of central europe and has also been called bachelors button. The allelopathic potential of tall hedge mustard was assessed using aqueous root and shoot extracts in seed germination and seedling growth bioassays. Flowering plants usually have 16 stems, but many have up to 20. Spotted knapweed also was thought to have been introduced in soil discarded in ship ballast. This insect can safely be considered the king of spotted knapweed biocontrol.
Nov 11, 2012 presently, the ecological importance of allelopathy on the invasion of spotted knapweed is uncertain and additional research is needed to determine if allelopathy does in fact account for the invasiveness of spotted knapweed and if so the identity of the allelochemical. Spotted knapweed, centaurea stoebe, early detection and rapid. Its name is derived from the black margins of the flower bract tips which give the flower heads a spotted look. Allelopathic able to stop the germination or growth of other plants, and can. However, the aggressive and competitive nature of the species may be more important than allelopathy in determining spotted knapweed success. The case against catechin involvement in allelopathy of. Spotted knapweed is found in artificial corridors such as gravel pits, railroad beds and field margins, and can spread to adjacent intact woodlands and prairies.
The flowers are pollinated predominately by bees and other small insects. Spotted knapweed, a classb nondesignate noxious weed in franklin county, washington centaurea biebersteinii is of the asteraceae family. In past times, young women wore spotted knapweed flowers to attract bachelors. Invasion biology introduced species summary project. Aster family asteraceae description spotted knapweed is a biennial or shortlived perennial. The common name spotted knapweed most often refers to centaurea maculosa. Progress 010105 to 123105 outputs we are exploring the origins of diffuse and spotted knapweed, allelopathy of spotted knapweed and the consequences of hybridization for biological control. As spotted knapweed seeds mature in late summer and fall, they can be spread on mowing equipment and in infested hay, seed, and gravel, or by hitchhiking on vehicles, other equipment, and even clothing. This larval feeding destroys knapweed s vascular root tissue and prevents the plant from transporting water and nutrients. Spotted knapweed is an aggressive, introduced weed species that rapidly invades pasture, rangeland, and fallow land and causes a serious decline in forage and crop production.
An allelopathic compound, cnicin, has been isolated from spotted knapweed leaves and shoots. Allelopathy two allelochemicals are produced and exuded by the roots of spotted knapweed, nicin and. A large, conspicuous insect, it lays its eggs on the top of the knapweed s root crown. Influence of spotted knapweed on diversity and abundance of. Previous work, using an activated carbon experiment, suggests allelopathic effects by spotted knapweed on native bunchgrasses ridenour and callaway 2001. Russian knapweed is the most difficult to handle, since this perennial knapweed digs in for the long haul it can set roots as deep as 20 feet below the surface of the soil. Knapweed is a dull green plant entirely covered with small, rough hairs. This phenomenon, called allelopathy, has been welldocumented in chaparral shrubs that secrete terpenes which inhibit the germination of wildflower seeds.
Spotted knapweed is listed as noxious, prohibited, banned or otherwise regulated in 16 states. We studied the allelopathic effects of spotted knapweed, centaurea maculosa, on associated species. United states department of agriculture natural resources. Spotted knapweed flower color ranges from white to dark purple. Spotted knapweed can grow up to 900 seeds per plant annually that are viable for up to 8 years. Knapweed reproduces by seed and can regenerate from the crown as well as by perennial root spread. Spotted knapweed, a classb nondesignate noxious weed in lincoln county, washington centaurea biebersteinii is of the asteraceae family. Spotted knapweed, centaurea stoebe, early detection and.
Spotted knapweed tolerates a wide range of temperature and moisture conditions, and is well adapted to openforest, pastures, and crp land in wisconsin. These insects cause plants to produce fewer viable seeds and to abort flowers. Foliage a basal rosette of deeply lobed leaves is produced the first year. This species is common throughout western north america but is not actually native to the north american continent, but to the eastern mediterranean.
Both knapweeds spread in alfalfa seed and hay before they were considered problem weeds. A study of the allelopathic effects of centaurea maculosa on. Spotted knapweed was first documented in north america in victoria, british columbia in 1893, and diffuse knapweed was first recorded in washington in 1907. Wicked weed of the west spotted knapweed is driving out native plants and destroying rangeland, costing ranchers millions. In early stages of growth, graygreen leaves are deeply lobed with short, thin, grayish hairs. It is often found in open, disturbed areas where it grows in tufted clumps. This document is hs944, one of a series of the horticultural sciences department, ufifas extension. Spotted knapweed is native to southeastern europe, and introduced to the whole of europe, northward to sweden fna 2006. The competitive advantages that spotted knapweed has over other species includes heavy seed production, 20,000 seeds or more royer and dickinson 1999, and the use of allelopathy. Plants profile for centaurea stoebe spotted knapweed. The decrease in acreage reported in montana is attributed to improved inventory methods during the past decade. Allelopathy can be defined as any direct or indirect harmful effect by one plant on another through the production of chemical compounds that escape into the environment.
Spotted knapweed national invasive species information. The flowers of spotted knapweed provide a good source of nectar for bees. The goal of this research was to explore the allelopathic influences of the exotic weeds tall hedge mustard sisymbrium loeselii l. The scientific name for spotted knapweed is centaurea maculosa lam.
The case against catechin involvement in allelopathy. Carney4 summary understanding the origins and basic biology of nonindigenous invasive plants can help lay a strong. This larval feeding destroys knapweeds vascular root tissue and prevents the plant from transporting water and nutrients. Seeds are dispersed by rodents, livestock and commercial hay. Spotted knapweed jan 2014 pdf 801 kb alberta invasive species council canada.
The plants database includes the following 1 subspecies of centaurea stoebe. In this study we collected and analyzed soil samples taken from three, longterm knapweed infested sites in montana, usa during the summer and fall of 2005. Sunflower family asteraceae native range central europe, east to central russia, caucasia, and western siberia description spotted knapweed is a biennial or shortlived perennial. A large, conspicuous insect, it lays its eggs on the top of the knapweeds root crown. Spotted knapweed has few natural enemies and is not preferred by livestock as forage. Please consult the plants web site and your state department of natural resources for this plants current status e.
Insects that eat spotted knapweed weedbusters biocontrol. The key to distinguishing spotted from other knapweeds is the blacktipped, spiny, involucral bracts phyllaries at the base of the flower. A single square foot of spotted knapweed can produce 5,000 seeds, which can remain viable for eight years or more. Catechinmetal interactions as a mechanism for conditional allelopathy by the invasive plant centaurea maculosa jarrod l. Upright stems are branched at the top and the stems are ribbed, and sometimes as they age they become hairless. After the eggs hatch, the larvae burrow into the root. It was introduced into north america as a contaminant in alfalfa medicago sativa in victoria, british columbia in 1883 sheley and petroff 1999. No evidence for rootmediated allelopathy in centaurea.
Origins, hybridization and allelopathy of spotted and. Yellow starthistle is another less robust annual type. Nu merous centaurea species introduced into the united states have become invasive, most notably, yellow st arthistle c. Chapter 11 sustainable control of spotted knapweed. University of nebraskalincoln extension ec173 revised. Bee keepers value the flowers of spotted knapweed because of the flavorful honey produced from its nectar. Wicked weed of the west science smithsonian magazine. Catechinmetal interactions as a mechanism for conditional. One potent allelopathic flavonoid called catechin is produced by the roots of spotted knapweed centaurea maculosa syn.
Allelopathy is a notoriously difficult mechanism to demonstrate. The taxonomy of spotted knapweed is discussed in ochsmann 7 and on the centaurea website. Although inventories are more common and more accurate, 50% of these states reported only 50% accuracy, while 31% reported 51 to 75% accuracy, and 2 states reported 75 to 100% accuracy. Centaurea diffusa, also known as diffuse knapweed, white knapweed or tumble knapweed, is a member of the genus centaurea in the family asteraceae. Spotted knapweed centaurea biebersteiniiherbaceous, shortlived perennial, 24 tall. A species profile for spotted knapweed from usda, national invasive species information center. Its name is derived from the spots formed by black margins on the flower bract tips. Oschmann 7 suggests that in north america, the name centaurea maculosa has been misapplied to centaurea stoebe ssp. It tends to grow to a height of 3 foot and has a single tap root that can go as deep as 18 inches. Comparing susceptibility of eastern and western us grasslands to competition and allelopathy from spotted knapweed centaurea stoebe l.
Two cytotypes of the plant exist which have been named as either different species or subspecies. Pdf comparing susceptibility of eastern and western us. The strategy spotted knapweed centaurea stoebe maculosa ssp. We compared small mammal abundance and diversity in areas with, and without, spotted knapweed in grand sable dunes, michigan, to determine whether presence of this plant affected the small mammal community. The hairy weevil eustenopus villosus that primarily attacks yellow starthistle has also been reported on spotted knapweed. Spotted knapweed produces chemicals that inhibit nearby plant growth, forming own habitat highly competitive with native vegetation, reducing forage for livestock and large game an hybridize with diffuse knapweed native to eurasia always read herbicide labels and follow instructions for use and ppe. Knapweed removal information how to get rid of knapweed. Spotted knapweed is native to central europe and east to central russia. Population structure, ploidy levels and allelopathy of. Allelopathic influence of tall hedge mustard sisymbrium.
Spotted knapweed can be identified from other centaurea species by the pronounced black tip on the bracts of the seed head. Presently, the ecological importance of allelopathy on the invasion of spotted knapweed is uncertain and additional research is needed to determine if allelopathy does in fact account for the invasiveness of spotted knapweed and if so the identity of the allelochemical. Centaurea maculosa spotted knapweed is an invasive species in north america, whose success has been attributed, at least in part, to the allelochemical root exudate. Spotted knapweed and diffuse knapweed are both shortlived perennials that sometimes behave like annuals.
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