1.Germination requirements? Seeds mainly germinate after autumn rains but a few shoot at other times when adequate moisture is available. “Although seeds can germinate at any time of year, there are two main germination times in late summer to autumn and late winter to spring”. (Bruzzese 1996).
2. Establishment requirements? Mostly occurs in ‘open’ areas/habitats, such as pastures, fields, etc. Also stated that ‘shade’ is known to inhibit C. Vulgare. Occurs in forest woodland. Carr et al. (1992).
3. How much disturbance is required? Occurs in minor disturbed ecosystems (e.g. wetlands, riparian areas), and highly disturbed areas (e.g. pastures, cultivated fields, waste places). However, mostly occurs in highly disturbed areas.
GROWTH / COMPETITIVE
4. Life form? Erect annual or biennial herb. Geophyte – fleshy storage, roots that can produce new aerial growth.
5. Allelopathic properties? None described.
6. Tolerates herb pressure? Not readily grazed by stock.
7. Normal growth rate? Competes with cereal crops.
8. Stress tolerance to frost, drought, w/logg, sal. etc? Tolerance to water logging assumed as occurs in riverine habitats (e.g., dam margins, riverbanks, wetlands). Occurs in locations where frosts would occur – Tasmania, Alaska, Canada and others.
REPRODUCTION
9. Reproductive system? Reproducing by seed: capable of both self-pollination and cross-pollination.
10. Number of propagules produced? Up to 200 flower heads and 8 000 seeds have been counted on individual plants.
11. Propagule longevity? A Canadian study shows some seed remaining viable for about 36 years.
12. Reproductive period? Annual or biennial.
13. Time to reproductive maturity? A flowering stem is produced in late spring of the 2nd year. Biennials. Annuals – first year.
DISPERSAL
14. Number of mechanisms? Wind, water, vehicles, machinery, animals, mud, pasture seed, contaminated hay.
15. How far do they disperse? “Most of the seeds land within a few metres of the parent plant and only about 10% are dispersed out of the local population”.
Impact Assessment
RECREATION
1. Restrict human access? “An erect perennial herb, commonly 15 to 35 cm high.” Its presence would not restrict human access.
2. Reduce tourism? Dense infestations are obvious, particularly during the flowering stage when areas are covered by a dense carpet of yellow flowers. Recreational activities not affected, but aesthetic of site would be.
3. Injurious to people? Although the plant is considered toxic to animals (it contains oxalic acid), “its flowering stems are occasionally chewed and sucked by children for the sour taste.” Toxicity is a problem of prolonged consumption. Consider mildly toxic.
4. Damage to cultural sites? Dense infestations would create a moderate negative visual impact.
ABIOTIC
5. Impact flow? Terrestrial species. P & C (2001)
6. Impact water quality? Terrestrial species.P & C (2001)
7. Increase soil erosion? During winter an extensive root system, consisting of several branched fleshy storage roots, develops. Rosettes grow rapidly through spring, reaching a diameter of about 60 cm. Normally, rosettes persist through summer and continue growth into the second autumn and winter.” Not likely to contribute to soil erosion.
8. Reduce biomass? “As a weed it occurs…particularly [in] annual pastures and neglected areas.” Dense infestations may increase biomass.
9. Change fire regime? “Dead plants often remain standing for one or two years.” In dense infestations this dry matter may lead to an increase in the frequency of fire risk.
COMMUNITY HABITAT
10(a) Impact on composition of high value EVC? EVC=Dry valley forest (V); CMA=West Gippsland; Bioreg=Highlands – Southern Falls; VH CLIMATE potential. Although it grows best on exposed sites, in Victoria, Australia, it is known to occur in a wide range of vegetation communities including woodlands and forests. It occurs in medium to large populations. The rosettes are large suppressing germination of other species. Carr et al. (1992) consider C. vulgare to be a serious threat to one or more vegetation formations in Victoria. Minor displacement of species in the lower stratum.
10(b) Impact on medium value EVC? EVC=Grassy woodland (D); CMA=East Gippsland; Bioreg=East Gippsland Uplands; H to VH CLIMATE potential. Impact as in 10(a) above.
10(c) Impact on low value EVC? EVC=Montane dry woodland (LC); CMA=East Gippsland; East Gippsland Uplands; VH CLIMATE potential. Impact as in 10(a) above.
11. Impact on structure? In Victoria, Australia, Cirsium vulgare invades a wide range of vegetation communities including woodlands and forests, and occurs in medium to large populations. Likely to have a major impact on 20 - 60% of the floral strata.
12. Effect on threatened flora? Not assessed.
FAUNA
13. Effect on threatened fauna? Not assessed.
14. Effect on non-threatened fauna? C. vulgare occurs in medium to large populations in a great number of vegetative communities. “Dense patches of spear thistle are common in much of southern Australia. The spiny nature of the plant deters animals from grazing” Infestations are likely to have minor reduction on habitat for fauna species.
15. Benefits fauna? No benefits to fauna species.
16. Injurious to fauna? No evidence of injury to fauna, however, animals avoid the plant due to its spiny nature, and dead plants can remain standing for one to two years. Potential to harm fauna species.
PEST ANIMAL
17. Food source to pests? Not documented as a food source to pests. However, the “fleshy roots of spear thistle have been prized in the past as a bait for rabbit poisoning,” and rabbits are known to use the plants for harbor. Rabbits may eat the roots of growing plants. Wild pigs love em.
18. Provides harbor? “…thick patches of the weed provide effective harbour for rabbits.” But only temporarily.
AGRICULTURE
19. Impact yield? A large spear thistle rosette covers about one-third of a square metre and, because it is not readily grazed by stock, the carrying capacity of paddocks with dense patches of thistle is reduced considerably.”
20. Impact quality? “…contaminated hay is downgraded in quality and price. The plant is an important component of vegetable fault of wool.”
21. Affect land values? “Spear thistle is so well established in much of southern Australia this it is accepted as a permanent part of the vegetation.” As such, its presence is unlikely to affect land values greatly.
22. Change land use? “The level of spear thistle infestations varies from year to year which reflects the changing opportunities for seedling establishment provided by climate and grazing pressure in the autumn.” Grazing activities may change somewhat to ensure minimal infestations to limit impact on agricultural return.
23. Increase harvest costs? Shearing costs may increase as, “spines in wool also cause difficulties in shearing.”
24. Disease host/vector? “There is veterinary evidence that the spiny leaves and bracts are responsible for transmitting virus diseases, including myxomatosis and scabby mouth, between animals.”
Uses
"Native North Americans used the newly bolted C. vulgare stems raw or cooked as food. The young leaves may be used for salads. The fleshy roots of C. vulgare have been sold commercially as bait for rabbit poisoning in Australia (Peterson, 1977; Mabberley, 1989). C. vulgare is a food source for bees (Barrow and Pickard, 1984). In Australia, it has value to the honey industry because it produces a good supply of nectar as well as pollen which is important for maintaining hives in some eucalypt areas. In ancient times, in Europe, it was used medicinally for treating haemorrhoids (Parsons and Cuthbertson, 1992)." [Source: CABI]
"A fibre obtained from the inner bark is used in making paper. The fibre is about 0.9mm long. The stems are harvested in late summer, the leaves removed and the stems steamed until the fibres can be stripped off. The fibres are cooked with lye for two hours and then put in a ball mill for 3 hours. The resulting paper is a light brown tan. The seed of all species of thistles yields a good oil by expression. No details of potential yields etc are given. The down makes an excellent tinder that is easily lit by a spark from a flint." [Source: wildfood.in/]
Management & Prevention
Cultural Control
The ability of thistles to invade pastures can be changed by grazing management (Sindel, 1991), primarily by changing the competitiveness of the desirable pasture species (Sindel, 1996). Sheep, goats and horses, but not cattle, have a significant effect on thistles in the early stages of infestation when they eat young plants (Wheatley, 1981; Olson and Lacey, 1994). In one study, J. Leigh (in Davidson, 1990) showed that goats, which have a reputation for eating everything, tend to avoid thistle foliage but ate all capitula of C. vulgare available to them and thus completely prevented seed dispersal from mature plants. Sheep grazing can reduce competition from neighbouring plants and increase seedling survival, growth, flowering and achene production in C. vulgare (Forcella and Wood, 1986a; Silvertown and Smith, 1989). The percentage of seedlings that survived through to the rosette stage was 1% under grazed conditions and 0.2% in ungrazed pastures (Forcella and Wood, 1986a). Bullock et al. (1994) found no effects of grazing on achene number per capitula, post-dispersal achene survival or between-year survivals in the seed bank. In New Zealand, frequent grazing and sowing of prairie grass cv. Matua, increased the establishment of C. vulgare (Pineiro and Harris, 1987). Establishing and maintaining dense, vigorous and competitive pasture can effectively prevent C. vulgare establishment as shown in swards of pasture species and legumes (Wardle et al., 1992). Stocking pastures is an essential step in thistle control. In Australia, conservation of ryegrass (Lolium rigidum) in pastures infested with C. vulgare has been recommended (Forcella and Wood, 1986a). An increase in ryegrass sowing density caused a decrease in C. vulgare biomass and increased time to flowering (Seefeldt and Armstrong, 2000). However, sowing C. vulgare achenes 12 months after the establishment of ryegrass did not affect emergence and survival of C. vulgare (Armstrong et al., 2002). [Source CABI 2015]
Mechanical Control
In pastures previously given weed control treatments, cultivation and cropping was a successful control method. Small areas can be eradicated by excavating the rosettes. Mowing and slashing can only be effective if done either immediately prior to flowering or when plants are just starting to flower (Sindel, 1991) otherwise flowering is merely delayed (Harris and Wilkinson, 1984). Cutting can reduce the number of thistles primarily by reducing achene input (Randall, 1990). The plants must be cut off below the soil surface and no leaves can remain attached or it will grow back. When mowing is carried out too early it may only delay flowering, however, if plants are cut too late in the flowering process viable seed may still develop in the capitula following cutting. As there can be a wide variation in the maturity of plants, a single mowing is unlikely to provide satisfactory control (Sindel, 1991) and repeated mowing throughout the entire growing season has proved successful (Wheatley, 1981). In addition, reduced vegetative matter from mowing will allow autumn use of herbicides to be more effective. Hand-pulling, hoeing and tillage can be successful if these operations are performed before the reproductive growth stages to prevent cypsela production (Beck, 1999). Besides encouraging competing vegetation where possible, every effort should be made to prevent established plants from going to seed. It is worth mentioning that this kind of control is very labour-intensive. [Source CABI 2015]
Biological Control
Biological control programmes against C. vulgare have been initiated in North America as a result of its invasiveness and associated economic losses. These include the release of a gall forming fruit fly, Urophora stylata (Tephritidae), and a thistle head weevil, Rhinocyllus conicus (Curculionidae) (Forcella and Randall, 1994). In Canada, U. stylata was released in 1973 and led to a 65% reduction in achene formation in some areas after three years (Parsons and Cuthbertson, 1992). This fruit fly is effective in controlling C. vulgare in central and western Europe, but results in North America show that fly dispersal is slow and the agent only survives in dense stands of C. vulgare (Harris and Wilkinson, 1984). R. conicus has a wide host range and can be a potential threat to native thistle species in North America (Turner et al., 1987). Its potential as a biocontrol agent has been investigated in Australia (Parsons and Cuthbertson, 1992). Two rosette-feeding weevils, Ceutorhynchus trimaculatus and Trichosirocalus horridus, were released in 1974 to control other carduine thistles in North America and have now spread to C. vulgare (Kok et al., 1979; McAvoy et al., 1987). None of these insects have provided adequate control of C. vulgare (Forcella and Randall, 1994). In Czechoslovakia, Terellia serratulae and U. stylata were recommended as biocontrol agents for C. vulgare. U. stylata produces galls in the flower heads of C. vulgare causing a reduction in the number of cypselas. T. serratulae does not produce galls but larvae of this species feeding on cypselas decrease seed production of the host plant. Larvae of both species can develop in the same flower head (Kinkorova, 1991). In South Africa, U. stylata from Germany and France and R. conicus from France were released on infestations of C. vulgare on several occasions from 1983 onwards. Initially, both herbivores became established and the results were modest (Zimmermann, 1990; 1991). However, the latest survey (Hodson et al., 2003) indicates that the contribution of R. conicus has been slight due to unidentified constraints, at least in the two localized areas that the weevils currently occupy. The fungus Sclerotinia sclerotiorum has been shown to have potential as a biological herbicide for controlling C. vulgare in pastures (Bourdôt and Harvey, 1996). [Source CABI 2015]
Integrated Control
Control methods that have been used to date are either not very effective and just temporarily remove C. vulgare from the site, or can be costly and detrimental to crops (Wheatley, 1981). The methods that are currently applied create many practical problems (Minehan, 1996), however, a combination of these methods may help prevent this species from further invasion. Pulling out the plants by hand, grazing young plants with goats or using herbicide on young plants to prevent seed set, seeding disturbed areas with competitive native perennials (Parsons and Cuthbertson, 1992) and soil solarization (Nasr-Esfahani, 1993) could all play a part of integrated management and control. Also, disturbance of soil and vegetation can advance germination (Klinkhamer and Jong, 1988) which may help synchronize the germination of C. vulgare and improve the effectiveness of chemical control. [Source CABI 2015]
Research
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