Bulky knapweed

Bulky knapweed
	Bulky knapweed ( Centaurea diffusa )
Systematics
Order :	Astern-like (Asterales)
Family :	Daisy family (Asteraceae)
Subfamily :	Carduoideae
Tribe :	Cynareae
Genre :	Knapweed ( Centaurea )
Type :	Bulky knapweed
Scientific name
	Centaurea diffusa
	Lam.

illustration

The Knapweed ( Centaurea diffusa ) is a plant from the genus of knapweed ( Centaurea ) within the family of Compositae (Asteraceae). Centaurea diffusa is together with the panicle knapweed ( Centaurea stoebe ) the typical "steppe runner" ( English tumbleweed ) as a neophyte in the western United States - the plant breaks off above the roots and, when blown away, spreads its seeds far and wide .

description

Parts of plants below and above ground

Total inflorescence with many flower heads

Flower heads in different stages in detail

Achenes with pappus

Vegetative characteristics

The chunky knapweed is an annual or biennial herbaceous plant that usually reaches heights of 10 to 60 centimeters. It has a strongly branched stem axis and a powerful tap root .

The leaves are arranged in a basal rosette and alternately distributed on the stem. The stem leaves are smaller than the basal leaves.

Generative characteristics

In a total inflorescence there are often many cup-shaped partial inflorescences . The flowers are usually white or pink.

Basal leaf rosette in the first year after germination

ecology

The chunky knapweed often takes the form of a rosette of leaves in the first year, which reaches its maximum width and then grows rapidly in height and flowers in the second year. A single plant can produce around 18,000 seeds .

Taxonomy

Centaurea diffusa was first published in 1785 by Jean-Baptiste de Lamarck in Encyclopédie Méthodique, Botanique , 1, 2, pages 675-676. Synonyms for Centaurea diffusa Lam. are: Acosta diffusa (Lam.) Soják , Centaurea microcalathina A. Tarass. , Centaurea cycladum Heldr. , Centaurea parviflora Sibth. & Sm. , Centaurea parviflora Besser , Centaurea parviflora Desf. , Centaurea comperiana Steven .

distribution

Centaurea diffusa is native to Asia Minor ( Turkey , Syria ), the Balkan Peninsula , ( Bulgaria , Greece , Romania ), Ukraine and southern Russia .

Habit as an invasive plant species

Invasive species

The chubby knapweed is considered an invasive species in some parts of North America that has established itself in many areas of the continent. It was first detected in North America in 1907 in an alfalfa field in Washington State . The seeds were presumably imported from the natural range in a contaminated shipment of alfalfa. Today the species is common in at least 19 of the United States. It has established populations in every state west of the Rocky Mountains and also in Connecticut , Massachusetts, and New Jersey . Parts of western Canada are also populated.

The areas where the chubby knapweed is found are usually flat pastureland and wooded embankments. The species prefers recently disturbed areas. It grows in semi-arid and arid areas and seems to prefer light, drought and well-aerated soils. Shading and high groundwater levels inhibit the growth of the chunky knapweed.

The spread is as follows:

Agriculture - Alfalfa seeds contaminated with chunky knapweed can promote spread.
Wildlife - Wildlife eat the seeds and excrete them elsewhere or spread the seeds in their fur.
Wind - Seeds blown out of the fruit heads are spread over short distances. However, when the plants dry out, they become steppe runners , rolling over great distances and releasing the achenes on the long journey.
Water - Streams of water carry the seeds over long distances until they are deposited on a bank and germinate.

Wind is the main means of spreading the chunky knapweed.

Effects

By 1998, the chunky knapweed had established itself on approximately 26,640 square kilometers in the western United States, expanding its range by 18% annually. The species can establish itself in grasslands , areas overgrown with shrubs and in habitats adjacent to water bodies. For the cattle it has little Futtwerwert since its thistle-like spines mouth and digestive tract can injure the animals that try to eat. A 1973 study concluded that ranchers lost about $ 20 per square kilometer because of the pastures degraded by chunky knapweed. On commercially used agricultural land, the yield and purity of the stands can be reduced considerably.

Combat

Effective control of the chunky knapweed requires the interaction of cultivation measures, biological, physical and chemical control as well as the reintroduction of native species. Any control measures must ensure that the root has been removed or the plant dies. In addition, the native flora should be promoted intensively in order to prevent the re-colonization of the bulky knapweed.

Biological control

Biological control involves the introduction of organisms, usually from competitors of the invasive species, into the affected areas. Twelve species of insects have been released since 1970 to combat the chunky knapweed. Of these twelve species, ten have become established and four have spread widely (the drill flies Urophora affinis and Urophora quadrifasciata, and the weevils Sphenoptera jugoslavica and Larinus minutus ). Research based on simulation models has shown that biological pest control is effective when it kills its host because the plants can otherwise compensate for the loss by increasing the number of seeds.

Some of the more commonly used biological pest control agents are:

The weevil Larinus minutus ( English Lesser knapweed flower weevil ): Individuals of this kind lay their eggs on both the achenes of saving Rigen knapweed as well as the panicles Knapweed ( Centaurea stoebe subsp. Stoebe ). When the larvae hatch from the egg, they eat the achenes from their host plants. Since the females of this species lay 28 to 130 eggs and each larva empties a complete achenes, a sufficiently large population of Larinus minutus can destroy a complete population of the chunky knapweed. The adult beetles feed on the shoot axes, leaves and undeveloped flowers. The beetles come from Greece and are now common in the states of Montana , Washington, Idaho and Oregon .
The weevil Cyphocleonus achates ( English Knapweed root weevil ): This species lays about 50 to 70 eggs on chubby or panicle knapweed. As the English name suggests, the larvae create feeding ducts in the roots of the plants, where they also undergo their metamorphosis into beetles. When this is complete, the beetles eat their way through the roots to the surface of the soil, where they feed on the leaves of the knapweed. The beetle was originally found in Austria , Greece, Hungary and Romania and was introduced in the states of Idaho, Montana, Washington and Oregon.
The moth Agapeta zoegana ( English Yellow-winged knapweed root moth ): This winder with root- -discriminatory larvae attacking saving Fingered and panicles flakes flowers in parts of the US, where he was introduced to combat.
Two types of bore flies ( Urophora affinis and Urophora quadrifasciata ): The females lay their eggs on the flower buds. The larvae form plant galls on the flower .

Physical combat

Physical control measures against the chunky knapweed include mowing, digging, or burning.

Mowing - While mowing the above-ground parts of the plant suppresses the spread of the seeds as much as possible, it does not remove the roots. However, with an intact root, the plant can survive and grow again. To be effective, mowing must continue for long periods of time so that there is a noticeable decrease in seeds.
Digging - This action removes both the aerial parts of the plant and its root and has proven to be very effective; if the plant is carefully removed, it can neither sprout nor spread its seeds. The biggest problem is that the workload is extremely high. In addition, the freed soil must be planted with native plants at the same time in order to prevent the re-establishment of the chunky knapweed on the disturbed area.
Burning - A fire that is sufficiently large can successfully destroy parts of the chunky knapweed above and below ground. However, precautions must be taken to ensure the fire does not spread and that a new plant community is established to prevent the knapweed from reintroducing itself.

Chemical control

Chemical control involves the use of herbicides . The preparation Tordon ( Picloram ) is considered to be the most effective, but it is common to use several herbicides to reduce the load on locally occurring grasses. The herbicides 2,4-D , dicamba and glyphosate are also effective for control. In order to be effective, the herbicides must be applied before the knapweeds have released the seeds, regardless of the agent used. Research from the University of Colorado suggests that the use of Tordon does nothing to reduce the long-term reduction of exotic species and even encourage the settlement of other invasive species ( Erodium cicutarium , Bromus japonicus ), which are rapidly taking the place of herbicide-treated chunky knapweed.

Human influence on the invasion

One of the first human influences on the chunky knapweed was the accidental introduction of the species into North America. There the species has established a distribution area that overshadows its original location.

It is known that the chunky knapweed establishes itself more easily and effectively on freshly disturbed surfaces. Disturbed habitats generally cause less environmental stress because more resources are available than are used. These available resources often allow community invasion to occur. The concentration of chunky knapweed in such an area is often associated with some degree of soil disturbance. Human disturbances often lead to lower biodiversity in a habitat. Conversely, lower diversity can lead to underutilized resources, which allows invasive species to take hold. Biotopes such as fallow land, irrigation ditches, pastures, residential and industrial areas and roadsides are all disrupted systems in which the chunky knapweed has established itself. Also, removing foliage or other ground cover material increases the likelihood that knapweed seeds will come into contact with the soil and germinate.

Possibly the greatest human influence on the chunky knapweed is the successful control and eradication of the invasive populations. The methods listed in the “Control” section represent a small selection of hundreds of approaches listed in the literature that have been attempted to control the species with varying degrees of success. In addition to reducing the spread of the bulky knapweed, specific pressure is also exerted on individual individuals who cannot withstand certain methods of control. If there is enough time, selective pressure can trigger an adaptation or evolution of such invasive species as the chunky knapweed. If a single chunky knapweed individual survives a control measure by virtue of its properties, its offspring will constitute a larger proportion within the population than those of the plants that were affected by the measure.

Towards an Integrated Combat Strategy

To successfully combat the chunky knapweed, an understanding of the mechanisms that allow the species to be invasive must be developed. This would make it possible to develop a targeted control method. In addition, precautions could be taken to minimize the impact on endangered habitats.

Summary

The success of the chunky knapweed must be attributed to a combination of several mechanisms. Their invasiveness is based on a mixture of allelopathy , the ERH (Enemy Release Hypothesis, German literally "enemy release hypothesis", i.e. the assumption that a species can become invasive if its enemies are not present in a habitat, i.e. if they are Enemy pressure ”is relieved and does not have to use resources to defend against it) and a superior use of resources. The greatest importance must be assigned to the ERH, because the chunky knapweed is a very effective invasive species in its new environment, while it does not occur invasively in its original home and does not form pure stands. It is the difference in biotic and abiotic environmental factors in the habitats that makes the species invasive.

To illustrate that the ERH applies to the chunky knapweed, it is essential to show that the absence of natural enemies has a significantly positive effect on its success. One way to prove this is to introduce some of their natural enemies into their new habitats. If the chubby knapweed, which generally thrives well in its new range, is significantly inhibited by the introduction of natural predators, it can be concluded that the species is more competitive in the absence of these predators. There is a current attempt to biologically control the chunky knapweed in Camas County , Idaho over 80 square kilometers with Larinus minutus and Cyphocleonus achates . Since both are among the chunky knapweed's natural enemies, and since these and other biological measures have been successful, there is significant evidence that the species benefits from the absence of its natural enemies.

Another aspect of the success of the chunky knapweed is based on the effects of allelopathic chemical substances in its new area of distribution. Although there is still discussion about the effectiveness of these substances in the field, it has already been proven in laboratory tests, and their tendency to form pure stands supports the importance of allelopathy for the sparse knapweed.

Strangely enough, the allelopathic substances of the chunky knapweed showed a negative effect on their North American competitors, but pushed the competitors out of the natural range. While the latter were more competitive under the influence of the allelopathic substances, the viability of the former decreased. This is an example of the effectiveness of the allelopathic mechanisms using the ERH. The increased effectiveness of the allelopathic substances means that the chunky knapweed is less exposed to enemy pressure. As a result, the species can establish itself dominantly in the new habitat.

Another relationship between allelopathy and the ERH is that the concentrations of the allelopathic substances were increased when the chunky knapweed grew in North American rather than Eurasian soils. This may be due to the absence of unfavorable soil conditions or of soil microorganisms that are present in the natural range. As a result, the allelopathic substances reach higher concentrations, spread further and are therefore more effective. When more neighboring plants are affected, the favorable soil conditions contribute to the success of the chunky knapweed.

In addition to the benefits that the chunky knapweed derives from ERH and allelopathy, it also possesses several characteristically invasive traits. One of their advantages is that they can be found in arid habitats. This advantage allows the way to use resources for the competitive struggle that the competitors need to survive. The high number of seeds produced is also found in other invasive species. A higher stand density will not only lead to a higher concentration of allelopathic substances in the soil, but also limit the amount of nutrients available to the native plants. Unfortunately, there is not enough research to determine the relative competitiveness of the bulky knapweed versus its competitors in the new range. However, there are studies on the effect of the chunky knapweed on North American grasses in the absence of allelopathic substances, which showed that the viability of these grasses decreased in the presence of the chunky knapweed. Unfortunately, it cannot be deduced from these data that the chunky knapweed is generally more competitive. Comparisons of adverse effects must be made between these and other combinations of species in order to arrive at such a conclusion.

The chunky knapweed is primarily successful in its new range because the organisms and conditions that keep it from becoming invasive in its traditional range are missing. It follows that the introduction of species from their ancestral range would be an effective control method. However, this carries the risk that these species could also become invasive. Therefore, every biological method must be checked for possible effects.

Common names

English common names are diffuse knapweed, white knapweed, tumble knapweed.

Individual evidence

^ P. Harris, R. Cranston: An economic evaluation of control methods for diffuse and spotted knapweed in western Canada . In: Canadian Journal of Plant Science volume = 59 . 1979, pp. 375-382.
↑ ^a ^b Centaurea diffusa at Tropicos.org. Missouri Botanical Garden, St. Louis, accessed September 2, 2019.
↑ Lamarck: Encyclopédie Méthodique, Botanique , 1, 2, 1785, pp. 675-676. scanned at botanicus.org .
^ ^A ^b ^c Judith H. Myers: Successful biological control of diffuse knapweed, Centaurea diffusa , in British Columbia, Canada . Biological Control. 2009. Archived from the original on June 11, 2010. Retrieved on December 18, 2009.
↑ JH Myers, C. Risley: Why reduced seed production is not necessarily translated into successful biological weed control . In: Montana State University (Ed.): Proceedings X. International Symposium Biological Control of Weeds . , Bozeman, MO2000, pp. 569-581.
↑ K. Groppe: Larinus minutus Gyll. (Coleoptera: Curculionidae), a suitable candidate for the biological control of diffuse and spotted knapweed in North America . In: Final Report CAB International Institute of Biological Control 1990, p. 30.

Web links

Commons : Bulky Knapweed ( Centaurea diffusa ) - Collection of images, videos, and audio files

USDA Species Profile - Diffuse Knapweed (Centaurea diffusa) .
Washington State Datasheet . (English)
Diffuse Knapweed (Centaurea diffusa)
HG Baker: The Evolution of Weeds . In: Annual Review of Ecology and Systematics . 5, 1974, pp. 1-24. doi : 10.1146 / annurev.es.05.110174.000245 .
K. Bossick, Wood River Journal . A16 (2004).
Ragan M. Callaway, Wendy M. Ridenour: Novel weapons: invasive success and the evolution of increased competitive ability . In: Front. Ecol. Environment . 2, No. 8, 2004, pp. 436-443. doi : 10.1890 / 1540-9295 (2004) 002 .
Ragan M. Callaway, Erik T. Aschehoug: Invasive Plants Versus Their New and Old Neighbors: A Mechanism for Exotic Invasion . In: Science . 290, No. 5491, 2000, pp. 521-523. doi : 10.1126 / science.290.5491.521 .
Alan T. Carpenter, Thomas A. Murray: ELEMENT STEWARDSHIP ABSTRACT for Centaurea diffusa Lamarck (synonym Acosta diffusa (Lam.) Sojak) diffuse knapweed . Retrieved August 9, 2019.
Chang-Hung Chou: Roles of Allelopathy in Plant Biodiversity and Sustainable Agriculture . In: Critical Reviews in Plant Sciences . 18, No. 5, 1999, pp. 609-636. doi : 10.1080 / 07352689991309414 .
David R. Clements, Antonio Di Tommaso, Nicholas Jordan, Barbara D. Booth, John Cardina, Douglas Doohan, Charles L. Mohler, Stephen D. Murphy, Clarence J. Swanton: Adaptability of plants invading North American cropland . In: Agriculture, Ecosystems & Environment . 104, No. 3, December 2004, pp. 379-398. doi : 10.1016 / j.agee.2004.03.003 .
Robert I. Colautti, Anthony Ricciardi, Igor A. Grigorovich, Hugh J. MacIsaac: Is invasion success explained by the enemy release hypothesis? . In: Ecology Letters . 7, 2004, pp. 721-733. doi : 10.1111 / j.1461-0248.2004.00616.x .
DJ Fielding, MA Brusven, LP Kish: Consumption of diffuse knapweed by two species of polyphagous grasshoppers (Orthoptera: Acrididae) in southern Idaho . In: Great Basin Naturalist . 562, 1996, pp. 22-27.
RJ Harrod, RJ Taylor: Reproduction and pollination biology of Centaurea and Acroptilon species, with emphasis on C. diffusa . In: Northwest Science . 69, 1995, pp. 97-105.
José L. Hierro, Ragan M. Callaway: Allelopathy and exotic plant invasion . In: Plant and Soil . 256, No. 1, 2003, pp. 29-39. doi : 10.1023 / A: 1026208327014 .
James S. Jacobs, Roger L. Sheley: Grass Defoliation Intensity, Frequency, and Season Effects on Spotted Knapweed Invasion . In: Journal of Range Management . 52, No. 6, November 1999, pp. 626-632.
Ryan M. Keane, Michael J. Crawley: Exotic plant invasions and the enemy release hypothesis . In: Trends in Ecology & Evolution . 17, No. 4, 2002, pp. 164-170. doi : 10.1016 / S0169-5347 (02) 02499-0 .
G. Kiemnec, L. Larson: Germination and root growth of two noxious weeds as affected by water and salt stresses . In: Weed Technology . 5, 1991, pp. 612-615.
K. Zouhar: Centaurea diffusa . In: Fire Effects Information System, [Online] . US Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). 2001. Retrieved August 9, 2019.
L. Larson: Centaurea diffusa . In: Global invasive species database . Invasive Species Specialist Group. Retrieved August 9, 2019.
L. Larson, G. Kiemnec: Seedling growth and interference of diffuse knapweed and bluebunch wheatgrass . In: Weed Technol. . 17, 2003, pp. 79-83.
JL Maron, M. Vila, R. Bommarco, S. Elmendorf, P. Beardsley: Rapid evolution of an invasive plant . In: Ecol. Monogr. . 74, 2004, pp. 261-280. doi : 10.1890 / 03-4027 .
Junya Mizutani: Selected Allelochemicals . In: Crit. Rev. Plant Sci. . 18, No. 5, 1999, pp. 653-671. doi : 10.1080 / 07352689991309432 .
Heinz Müller-Schärer, Urs Schaffner, Thomas Steinger: Evolution in invasive plants: implications for biological control . In: Trends in Ecology & Evolution . 19, No. 8, 2004, pp. 417-422.
Miquel Palmer, Marta Linde, Guillem X. Pons: Correlational patterns between invertebrate species composition and the presence of an invasive plant . In: Acta Oecologica . 26, No. 3, December 2004, pp. 219-226. doi : 10.1016 / j.actao.2004.05.005 .
RD Powell: The role of spatial patterns in the population biology of Centaurea diffusa . In: Journal of Ecology . 78, 1990, pp. 374-388.
Elroy L. Rice: Some roles of allelopathic compounds in plant communities . In: Biochemical Systematics and Ecology . 5, No. 3, 1977, pp. 201-206. doi : 10.1016 / 0305-1978 (77) 90005-9 .
Ann K. Sakai, Fred W. Allendorf, Jodie S. Holt, David M. Lodge, Jane Molofsky, Kimberly A. With, Syndallas Baughman, Robert J. Cabin, et al .: The Population Biology of Invasive Species . In: Annual Review of Ecology and Systematics . 32, November 2001. doi : 10.1146 / annurev.ecolsys.32.081501.114037 .
TR Seastedt, Nathan Gregory, David Buckner: Effect of biocontrol insects on diffuse knapweed (Centaurea diffusa) in a Colorado grassland . In: Weed Science . 51, No. 2, April 2003, pp. 237-245. doi : 10.1614 / 0043-1745 (2003) 051 .
Roger L. Sheley, James S. Jacobs, Michael F. Carpinelli: Distribution, Biology, and Management of Diffuse Knapweed ( Centaurea diffusa ) and Spotted Knapweed ( Centaurea maculosa ) . In: Weed Technology . June 12, 2017. doi : 10.1017 / S0890037X00043931 .
DJ Thompson, DG Stout: Duration of the juvenile period in diffuse knapweed (Centaurea diffusa) . In: Canadian Journal of Botany . 69, 1991, pp. 368-371.
Montserrat Vilà, Jacob Weiner: Are invasive plant species better competitors than native plant species? - evidence from pair-wise experiments . In: Oikos . 105, No. 2, May 2004, pp. 229-238. doi : 10.1111 / j.0030-1299.2004.12682.x .
Jorge M. Vivanco, Harsh P. Bais, Frank R. Stermitz, Giles C. Thelen, Ragan M. Callaway: Biogeographical variation in community response to root allelochemistry: novel weapons and exotic invasion . In: Ecology Letters . 7, No. 4, April 2004, pp. 285-292. doi : 10.1111 / j.1461-0248.2004.00576.x .
Leslie A. Weston, Stephen O. Duke: Weed and Crop Allelopathy . In: Critical Reviews in Plant Sciences . 22, No. 3-4, 2003, pp. 367-389. doi : 10.1080 / 713610861 .
Anthony J. Willis, Matthew B. Thomas, John H. Lawton: Is the increased vigor of invasive weeds explained by a trade-off between growth and herbivore resistance? . In: Oecologia . 120, No. 4, September 1999, pp. 632-640. doi : 10.1007 / s004420050899 .
Rob Wilson, K. George Beck, Philip Westra: Combined effects of herbicides and Sphenoptera jugoslavica on diffuse knapweed (Centaurea diffusa) population dynamics . In: Weed Science . 52, No. 3, June 2004, pp. 418-423. doi : 10.1614 / P2001-061 .
Dale K. Whaley, Gary L. Piper: Defusing Diffuse Knapweed - Biological Control of an Explosive Weed . In: Agrichem. Environ. News . No. 194, June 2002.

[Cranston1979-1] P. Harris, R. Cranston: An economic evaluation of control methods for diffuse and spotted knapweed in western Canada . In: Canadian Journal of Plant Science volume = 59 . 1979, pp. 375-382.

[Tropicos-2] Centaurea diffusa at Tropicos.org. Missouri Botanical Garden, St. Louis, accessed September 2, 2019.

[Lamarck1785-3] Lamarck: Encyclopédie Méthodique, Botanique , 1, 2, 1785, pp. 675-676. scanned at botanicus.org .

[Myers2009-4] A ^b ^c Judith H. Myers: Successful biological control of diffuse knapweed, Centaurea diffusa , in British Columbia, Canada . Biological Control. 2009. Archived from the original on June 11, 2010. Retrieved on December 18, 2009.

[Myers2000-5] JH Myers, C. Risley: Why reduced seed production is not necessarily translated into successful biological weed control . In: Montana State University (Ed.): Proceedings X. International Symposium Biological Control of Weeds . , Bozeman, MO2000, pp. 569-581.

[Groppe1990-6] K. Groppe: Larinus minutus Gyll. (Coleoptera: Curculionidae), a suitable candidate for the biological control of diffuse and spotted knapweed in North America . In: Final Report CAB International Institute of Biological Control 1990, p. 30.