Spotted knapweed | |
---|---|
Scientific classification | |
Kingdom: | Plantae |
Clade: | Tracheophytes |
Clade: | Angiosperms |
Clade: | Eudicots |
Clade: | Asterids |
Order: | Asterales |
Family: | Asteraceae |
Genus: | Centaurea |
Species: | C. stoebe |
Binomial name | |
Centaurea stoebe | |
Centaurea stoebe, the spotted knapweed or panicled knapweed, [1] is a species of Centaurea native to eastern Europe, although it has spread to North America, where it is considered an invasive species. It forms a tumbleweed, helping to increase the species' reach, and the seeds are also enabled by a feathery pappus.
Centaurea stoebe is a biennial or short-lived perennial plant, and it usually has a stout taproot and pubescent stems when young. It has pale and deeply-lobed leaves covered in fine short hairs. First-year plants produce a basal rosette, alternate, up to 15 centimetres (6 inches) long, deeply divided into lobes. [2] It produces a stem in its second year of growth. Stem leaves are progressively less lobed, getting smaller toward the top. The stem is erect or ascending, slender, hairy and branching, and can grow up to 0.91 metres (3 feet) tall. Protruding from black-tipped sepals, the flower blooms from July to September. [3] The flower head is 10 millimetres (3⁄8 in) wide, with vibrant pink to lavender (or more rarely white) disc flowers around 2 cm (3⁄4 in) long; the corolla of each has five narrow lobes. [3] The fruit is an achene about 6.4 mm (1⁄4 in) long with a short, bristly pappus. These are primarily dispersed by wind, sometimes assisted by the plant's tumbleweed mode. [4]
C. stoebe was formerly known as C. maculosa. Two[ specify ] cytotypes of C. stoebe exist which have been considered as different species by some taxonomists. The diploid form of the plant is now called C. stoebe L. spp. stoebe, while the tetraploid is known as C. stoebe L. spp. micranthos or by some taxonomists as C. biebersteinii DC. [5] The names of C. stoebe and C. biebersteinii may have been accidentally switched early in the plant's taxonomic history. [3]
The common name spotted knapweed refers to the black-tipped sepals that look like spots.
The species is native to eastern Europe. [6] [7] It is also an invasive species in southern Canada, and northwestern Mexico, and nearly every state in the United States; it has thrived in the western US in particular, much of which has a dry climate similar to the Mediterranean.
The plant grows on stream banks, pond shorelines, sand prairies, old fields and pastures,[ citation needed ] roadsides, along railroads, and in many open and disturbed areas. [3] It is relatively tolerant of cold and reaches into alpine environments. [8]
Centaurea stoebe has been introduced to North America, [9] where it is considered an invasive species in much of the western US and Canada. In 2000, C. stoebe occupied more than 7 million acres (28,000 square kilometres) in the US. [10]
Spotted knapweed is a pioneer species found in recently disturbed sites or openings, growing in dense stands. [3] As such, human disturbance is a major cause of infestations. It readily establishes itself and quickly expands in places of human disturbance such as industrial sites, [11] along roadsides, and along sandy riverbanks. Once established, it also has the potential to spread into undisturbed natural areas. [2] Because cattle prefer the native bunchgrass over knapweed, overgrazing can often increase the density and range of knapweed infestations. [12] This species is believed to have several traits that contribute to its extreme competitive ability:[ citation needed ]
A study conducted in 2003 has shown that with future global atmospheric carbon levels, C. stoebe shows increased growth with increased atmospheric carbon which could potentially expand its range and outcompete native species. [13]
Spotted knapweed likely spread to North America in an alfalfa shipment. It was first recorded in Bingen, Klickitat County, Washington, in the late 1800s. By 1980, it had spread to 26 counties in the Pacific Northwest. [14] In the year 2000, it was reported in 45 of the 50 states of the US. Spotted knapweed primarily affects rangelands of the northwest US and Canada. [15] A 1996 study estimated the direct plus secondary economic impact of spotted knapweed in Montana to be approximately $42 million annually. [16] When spotted knapweed replaces native grasses, soil erosion and surface runoff are increased, [17] depleting precious soil resources.
In 2015, a Missoula, Montana, beekeeper whose bees rely on local knapweed stated that "knapweed produces great honey ... people should consider planting native wildflowers instead of just taking out weeds." [18]
The roots of Centaurea stoebe exude (-)-catechin, which has been proposed to function as a natural herbicide that may inhibit competition by a wide range of other plant species. [19] While this phytotoxic compound can inhibit seed germination and growth at high concentrations, it is debated whether concentrations in field soils are high enough to affect competition with neighboring plants. Several high-profile papers arguing for the importance of catechin as an allelochemical were retracted after it was found that they contained fabricated data showing unnaturally high levels of catechin in soils surrounding C. stoebe. [20] [21] Subsequent studies from the original lab have not been able to replicate the results from these retracted studies, nor have most independent studies conducted in other laboratories. [22] [23] Thus, it is doubtful whether the levels of (-)-catechin found in soils are high enough to affect competition with neighboring plants. The proposed mechanism of action (acidification of the cytoplasm through oxidative damage) has also been criticized, on the basis that (-)-catechin is actually an antioxidant. [23]
An 8-year study in Michigan found that restoring native plant communities in knapweed-infested sites requires multi-faceted and multi-year approaches. This includes an initial site preparation by mowing and an optional application of a clopyralid or glyphosate herbicide followed by reseeding with the desired plant communities. Yearly hand pulling of C. stoebe over the course of the study virtually eradicated the infestation. Burning treatments of infested sites reduced the labour needs for pulling and encouraged native plant community establishment. [24]
Another study over 3 years comparing the effectiveness of different combinations of annual spring, summer, and fall mowing treatments recommends an annual fall mowing during the flowering or seed-production stage in controlling C. stoebe infestations. [25]
Thirteen biological pest control agents have been used against this plant and its congener, diffuse knapweed (C. diffusa), including the moths, Agapeta zoegana and Metzneria paucipunctella ; the weevils, Bangasternus fausti , Larinus obtusus , Larinus minutus and Cyphocleonus achates ; and the fruit flies, Chaetorellia acrolophi , Urophora affinis and Urophora quadrifasciata . [26] Although the number of seeds is significantly reduced, this is not enough to make biocontrol truly effective against C. stoebe. [3] [27] In some instances, root-herbivory on C. stoebe stimulates additional release of catechin, which may function as an allelopathic toxin. [28] In addition, moderate levels of herbivory by biocontrol agents can cause compensatory growth. [29]
Prescribed grazing may be an effective means of controlling infestations, as all growth forms of C. stoebe are nutritious to sheep. High-density infestations can be controlled by fencing in the affected area with sheep until the desired level of removal is achieved. [30]
Detection dogs can be trained to locate small infestations of invasive, non-native weeds. Previous methods of detection involved lining up dozens of volunteers to locate the small rosettes buried somewhere on a large parcel of land covered with other vegetation.
Montana State University successfully completed field testing in 2004. The dog, Knapweed Nightmare was finding low densities of the non-native invasive knapweed plant in the field with an overall success rate of 93%. [31] She followed it up with 98% in the final trials in open fields, demonstrating that dogs can effectively detect low densities of invasive plants. [32]
Handling the plant barehanded is rumored to possibly cause tumors, particularly if one has an open wound, but there is little evidence to support this hypothesis. [3] [4]
Centaurea is a genus of over 700 species of herbaceous thistle-like flowering plants in the family Asteraceae. Members of the genus are found only north of the equator, mostly in the Eastern Hemisphere; the Middle East and surrounding regions are particularly species-rich.
Onopordum acanthium is a flowering plant in the family Asteraceae. It is native to Europe and Western Asia from the Iberian Peninsula east to Kazakhstan, and north to central Scandinavia, and widely naturalised elsewhere, with especially large populations present in the United States and Australia. It is a vigorous biennial plant with coarse, spiny leaves and conspicuous spiny-winged stems.
Allelopathy is a biological phenomenon by which an organism produces one or more biochemicals that influence the germination, growth, survival, and reproduction of other organisms. These biochemicals are known as allelochemicals and can have beneficial or detrimental effects on the target organisms and the community. Allelopathy is often used narrowly to describe chemically-mediated competition between plants; however, it is sometimes defined more broadly as chemically-mediated competition between any type of organisms. The original concept developed by Hans Molisch in 1937 seemed focused only on interactions between plants, between microorganisms and between microorganisms and plants. Allelochemicals are a subset of secondary metabolites, which are not directly required for metabolism of the allelopathic organism.
Centaurea diffusa, also known as diffuse knapweed, white knapweed or tumble knapweed, is a member of the genus Centaurea in the family Asteraceae. This species is common throughout western North America but is not actually native to the North American continent, but to the eastern Mediterranean.
Centaurea solstitialis, the yellow star-thistle, is a species of thorny plant in the genus Centaurea, which is part of the family Asteraceae. A winter annual, it is native to the Mediterranean Basin region and invasive in many other places. It is also known as golden starthistle, yellow cockspur and St. Barnaby's thistle.
Agapeta zoegana is a species of moth known as the sulphur knapweed moth and the yellow-winged knapweed root moth. It is used as an agent of biological pest control against noxious knapweeds, particularly spotted knapweed and diffuse knapweed.
Bangasternus fausti is a species of true weevil known as the broad-nosed seed head weevil. It is used as an agent of biological pest control against noxious knapweeds, particularly spotted knapweed, squarrose knapweed, and diffuse knapweed.
Chaetorellia acrolophi is a species of tephritid fruit fly known as the knapweed peacock fly. It is used as an agent of biological pest control against noxious knapweeds, especially spotted knapweed.
Cyphocleonus achates is a species of true weevil known as the knapweed root weevil. It is native to southern Europe and the Mediterranean and is used as an agent of biological pest control against noxious knapweeds, especially spotted knapweed. It has recently been spotted in India.
Larinus minutus is a species of true weevil known as the lesser knapweed flower weevil. It is used as an agent of biological pest control against noxious knapweeds, especially diffuse knapweed and spotted knapweed.
Bangasternus orientalis is a species of true weevil known as the yellow starthistle bud weevil. It is used as an agent of biological pest control against the noxious weed yellow starthistle.
Centaurea virgata is a species of Centaurea. It is native to Western Asia. The subspecies C. virgata subsp. squarrosa is known as squarrose knapweed.
Urophora affinis is a species of tephritid or fruit flies in the genus Urophora of the family Tephritidae. It has been released in the United States and Canada as a biocontrol agent to control spotted knapweed. U. affinis became established in Montana in 1973.
Puccinia jaceae var. solstitialis is a species of fungus in the Pucciniaceae family. It is a plant pathogen that causes rust. Native to Eurasia, it is the first fungal pathogen approved in the United States as a biological control agent to curb the growth of the invasive weed yellow starthistle.
Taeniatherum is a genus of Eurasian and North African plants in the grass family.
Pterolonche inspersa, sometimes called the brown-winged knapweed root moth, is a small moth of the family Pterolonchidae.
Ecologically based invasive plant management (EBIPM) is a decision-making framework to improve the management of invasive plant species. When land managers are faced with infestations of invasive plants, a step by step framework to develop integrated management plans will improve their success at managing these plants. EBIPM is founded on the principles of ecology to manage invasive weed infestations and restore landscapes. The framework combines an ecosystem health assessment, a method to recognize how ecological processes affect causes of succession, ecological principles to guide the choices of tools and strategies to manage invasive plants and how to use adaptive management to generate a step-by-step decision model. The focus of EBIPM is to encourage managers to move away from simply killing the weeds and move toward management efforts that repair the underlying causes of invasion.
Garlic mustard was introduced to North America as a culinary herb in the 1860s and it is considered an invasive species in much of North America. As of 2020 it has been documented in most of the Eastern United States and Canada, with scattered populations in the west. It is listed as a noxious or restricted plant in the following states: Alabama, Connecticut, Massachusetts, Minnesota, New Hampshire, Oregon, Vermont, and Washington. A current map of its distribution in the United States can be found at the Early Detection and Distribution Mapping System (EDDmapS).
Meadow knapweed, also known as hybrid knapweed or protean knapweed, is a fertile hybrid between black knapweed and brown knapweed. The taxonomic status of the species is uncertain, and meadow knapweed has been variously described as different species.
Knapweed Nightmare was the first dog trained "to locate a plant within a plant community" which enabled her to track down low densities of invasive non-native noxious weeds. Nightmare is a sable shepherd dog trained by Montana based, Rocky Mountain Command Dogs.