Senecio jacobaea (common ragwort)
- Summary of Invasiveness
- Taxonomic Tree
- Notes on Taxonomy and Nomenclature
- Plant Type
- Distribution Table
- History of Introduction and Spread
- Risk of Introduction
- Habitat List
- Hosts/Species Affected
- Biology and Ecology
- Latitude/Altitude Ranges
- Air Temperature
- Rainfall Regime
- Soil Tolerances
- Natural enemies
- Notes on Natural Enemies
- Means of Movement and Dispersal
- Pathway Vectors
- Plant Trade
- Impact Summary
- Environmental Impact
- Impact: Biodiversity
- Social Impact
- Risk and Impact Factors
- Similarities to Other Species/Conditions
- Prevention and Control
- Distribution Maps
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PicturesTop of page
IdentityTop of page
Preferred Scientific Name
- Senecio jacobaea L.
Preferred Common Name
- common ragwort
Other Scientific Names
- Jacobaea vulgaris Gaertn.
- Senecio dimorphocarpos Col.
International Common Names
- English: ragweed; ragwort; tansy ragwort
- Spanish: hierba lombriguera
- French: herb St. Jacques
- Russian: krestovnik yakova
- Portuguese: tasna; tasneira
Local Common Names
- Austria: Jacobs-Kreuzkraut
- Canada: baughlan
- France: fleur de Saint-Jacques; herbe dorée; seneçon Jacobée
- Germany: Jacobs-Kreuzkraut
- Hungary: Jakabnapi aggófû
- Ireland: benweed
- Italy: erba san Jacobo; jacobea
- Netherlands: Jakobskruiskruid
- Norway: landoyda
- Poland: starzec jakubek
- Romania: jakabnapi aggófu; petimbroasa
- Sweden: vanliga Jacobsörten
- Switzerland: Jacobs-Kreuzkraut
- UK: bragweed; bunnel; bunwede; bunweed; cammock; cankerweed; cankerwort; cheadle-dock; cow foot; cows foot; cradle-dock; cushag; devil dums; dog standard; fairies' horse; felon weed; field ragwort; fizz gigs; flee dod; fleenurt; fleewort; fly flower; gander-goose; gipsy; grand swaith; hammerwort; herb St. James; kadle-dock; kedlock; ketlock; marefart; mountain ragwort; muggart; muggart Kail; ragged Jack; ragged Robin; rayless ragwort; scattle-dock; scrape-clean; scrog; seg rum; seggy; sigrum; sleepy-dose; St. James' flower; staggerwort; stammer wort; stanerwort; stinking alisander; summer's farewell; swine's cress; swine's grass; tansy; tirso; water groundsel; weeby; wild chrysanthemum; yack-yard; yallers; yarkrod; yellow daisy; yellow elshinders
- USA: cankerweed; fairies-horse; felon weed; kettle-dock; Saracen's compass; St. James' wort; staggerwort; stavewort
- SENJA (Senecio jacobaea)
Summary of InvasivenessTop of page
Taxonomic TreeTop of page
- Domain: Eukaryota
- Kingdom: Plantae
- Phylum: Spermatophyta
- Subphylum: Angiospermae
- Class: Dicotyledonae
- Order: Asterales
- Family: Asteraceae
- Genus: Senecio
- Species: Senecio jacobaea
Notes on Taxonomy and NomenclatureTop of page
Based on DNA sequence data from the chloroplast and nuclear genomes, Pelser et al. (2002) showed that Senecio section Jacobaea was monophyletic, and that of the 15 section Jacobaea species sampled, S. jacobaea was found in a monophyletic clade that comprised S. chrysanthemoides DC., S. cineraria DC., S. ambiguous DC., S. alpinus (L.) Scop., S. aquaticus Hill, S. pancicii Degen and S. subalpinus Koch.
Fisher (1932) suggests two origins of the vernacular name 'ragwort': (i) as a reference to the somewhat ragged leaf of the mature plant; and (ii) from the Anglo Saxon 'aege' meaning 'goat' and 'wort' meaning 'plant' with (fanciful) reference to the apparent similarity of the fruit heads to a goat's beard. Grigson (1974) supports the former view, and considers the name 'ragwort' to be of 15th century origin. Hunt (1989) gives regedewort and electarus as Medieval English names for S. jacobaea. Staggerwort appears to be a reference to the toxic effects of S. jacobaea on livestock, although Grieve (1931) cites an unnamed source to indicate that S. jacobaea was a remedy for staggers in horses! St. James' wort and the Italian, French and German vernacular names and the scientific name are a reference to the plant flowering around St. James' day (25th July). In about 1831, John Clare (Williams and Williams, 1986) famously wrote 'The Ragwort' about the beauty of S. jacobaea, and it attracted the 'poetic' attention of Barker (1925).
In databases and on the Web, the 'ae' diphthong in 'jacobaea' is often, incorrectly, transcribed as either 'jacobea' or 'jacobae'.
DescriptionTop of page
Plant TypeTop of page
DistributionTop of page
Distribution TableTop of page
The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.Last updated: 17 Feb 2021
|Continent/Country/Region||Distribution||Last Reported||Origin||First Reported||Invasive||Reference||Notes|
|Algeria||Present||Native||Original citation: Quezel and Santa (1963)|
|South Africa||Absent, Formerly present|
|China||Present||Native||Original citation: Hultén & Fries, 1986|
|Japan||Present||Present based on regional distribution.|
|Bosnia and Herzegovina||Present, Widespread||Native|
|Federal Republic of Yugoslavia||Present, Widespread||Native|
|Malta||Absent, Formerly present|
|North Macedonia||Present, Widespread||Native|
|Russia||Present||Present based on regional distribution.|
|-Central Russia||Present, Widespread||Native|
|-Eastern Siberia||Present, Widespread||Native|
|-Southern Russia||Present, Widespread||Native|
|-Western Siberia||Present, Widespread||Native|
|United Kingdom||Present, Widespread||Native||Invasive|
|-Channel Islands||Present, Widespread||Native|
|Canada||Present||Present based on regional distribution.|
|-British Columbia||Present, Widespread||Introduced||Invasive||First reported: c. 1913|
|-New Brunswick||Present, Widespread||Introduced||Invasive||First reported: pre-1884|
|-Newfoundland and Labrador||Present, Widespread||Introduced||Invasive|
|-Nova Scotia||Present, Widespread||Introduced||Invasive||First reported: c. 1853|
|-Ontario||Present, Widespread||Introduced||Invasive||First reported: c. 1861|
|-Prince Edward Island||Present, Widespread||Introduced||Invasive||First reported: c. 1888|
|Saint Pierre and Miquelon||Present, Widespread||Introduced||Invasive|
|Trinidad and Tobago||Present||Introduced|
|United States||Present||Present based on regional distribution.|
|Australia||Present||Present based on regional distribution.|
|-South Australia||Present, Localized||Introduced||1954||Invasive|
|-Victoria||Present, Localized||Introduced||Invasive||First reported: 1880-1890|
|New Zealand||Present, Widespread||Introduced||1874||Invasive|
|Argentina||Absent, Formerly present|
History of Introduction and SpreadTop of page
S. jacobaea was introduced to Victoria (Australia) from Europe between 1880 and 1890 (Schmidl, 1972), and is a particular problem in the south-east of the state. The first record from South Australia was in 1954 (Black, 1957). Localized outbreaks occur in the high rainfall (>750 mm) areas of Western Australia (Department of Agriculture - Western Australia, 2002). In New Zealand, S. jacobaea was first reported in 1874 (Allan, 1940), and is common over both the North and South Islands.
Harper and Wood (1957), and subsequent authors, identified S. jacobaea as an exotic in South Africa and Argentina. However, a search of the recent flora records for these two countries revealed no references to the occurrence of S. jacobaea; although other hepatotoxic Senecio species do occur in these countries. Grime et al. (1988) argue that S. jacobaea may be declining in many areas of the UK, although Preston et al. (2002) note that the distribution of S. jacobaea does not appear to have changed over the last 40 years.
Risk of IntroductionTop of page
S. jacobaea is one of five species listed under the UK Weeds Act 1959 and the Town and Country Planning Act 1990. In the Weeds Act, primary responsibility for control rests with the occupier of any land on which the plants are growing. Where there is a risk that S. jacobaea might spread, the Minister of Agriculture can serve a notice on the occupier of the land requiring action to be taken to prevent its spread (Roberts, 1982). However, in practice, 'priority is given to those complaints where there is a threat to farmland or land that is being used for the keeping of horses as part of a diversified farm business' (Alun Michael, House of Commons, UK, 7th November 2002); pressure groups interested in equines are campaigning to amend the Weeds Act 1959, although such campaigns have been criticised (Cook, 2003).
S. jacobaea is listed as a prohibited noxious weed (Class I) under the Canada Seeds Order (Anon., 1986a), and is listed under Weed Control Acts in British Columbia and Nova Scotia (NSDAM, 1977; Anon., 1986b). S. jacobaea is covered by Federal and State quarantine laws in Arizona, California, Colorado, Idaho, Montana and Washington (National Plant Board, 2003). In addition, S. jacobaea is listed as a noxious weed in Colorado (Colorado State Code, 2000) and Idaho (Idaho Department of Agriculture, 1993), a prohibited noxious weed in Arizona (Arizona Department of Agriculture, 1996), a Class B noxious weed in California (California Department of Food and Agriculture, 1998) and Washington (Washington Department of Agriculture, 1992, 1997) and Class B designated weed in Oregon (Oregon Department of Agriculture, 1997a, b).
In Australia, S. jacobaea is a proclaimed plant that is notifiable throughout the state of South Australia, under the Animal and Plant Control Act 1986 (Animal & Plant Control Commission, 1999). In Tasmania, S. jacobaea is a noxious weed under the Noxious Weeds Act 1964 and the Weed Management Act 1999 (DPIWE, 2003). In Western Australia, S. jacobaea is a declared noxious weed (Department of Agriculture - Western Australia, 2002). In New Zealand, S. jacobaea is prohibited under the Biosecurity Act 1993 (MAF Biosecurity Authority, 2002).
HabitatTop of page
Habitat ListTop of page
|Terrestrial||Managed||Managed forests, plantations and orchards||Present, no further details|
|Terrestrial||Managed||Managed grasslands (grazing systems)||Present, no further details||Harmful (pest or invasive)|
|Terrestrial||Managed||Disturbed areas||Present, no further details||Harmful (pest or invasive)|
|Terrestrial||Managed||Rail / roadsides||Present, no further details||Harmful (pest or invasive)|
|Terrestrial||Managed||Urban / peri-urban areas||Present, no further details|
|Terrestrial||Natural / Semi-natural||Natural grasslands||Present, no further details||Harmful (pest or invasive)|
|Littoral||Coastal areas||Present, no further details||Harmful (pest or invasive)|
Hosts/Species AffectedTop of page
Biology and EcologyTop of page
A chromosome number of 2n = (4x) = 40 has commonly been reported for European material, although 2n = (8x ) = 80 has also been recorded (e.g., Bolkhovskikh et al., 1969; Moore, 1973). Chromosome number appears to be independent of infraspecific boundaries (Kadereit and Sell, 1986). Böcher and Larsen (1955) record a chromosome number of 2n = 32 (which needs to be confirmed) from S. jacobaea material collected from sand dunes in County Donegal (Ireland), which Kadereit and Sell (1986) suggest might be S. jacobaea subsp. jacobaea var. condensatus. Hybridization is recorded in the UK and Ireland with S. aquaticus L. (as S. x ostenfeldii Druce), S. erucifolius L. (as S. x liechtensteinensis Murr., syn. S. x whitwellianus Lees ex Cheetham nomen nudum) and S. cineraria DC. (a garden escape in the UK; as S. x albescens Burbridge & Colgan) (Benoit et al., 1975), in Germany with S. aquaticus (Hegi, 1929), in Austria and Liechtenstein with S. erucifolius (Hegi, 1929) and in Germany, Austria, Tyrol and Switzerland with S. alpinus (L.) Scop. (as S. x reisachii Gremblich and S. x eversii Huter; Hegi, 1929). Chater and Walters (1976) indicate that hybrids between S. jacobaea and S. aquaticus occur occasionally in Central and Western Europe. Benoit et al. (1975) question the reliability of the UK and Continental records of hybrids between S. jacobaea and S. erucifolius, and the Irish records of hybridization between S. jacobaea and S. squalidus. Hybrids between S. aquaticus and S. jacobaea are partially fertile, morphologically variable and often form hybrid swarms (Harper and Wood, 1957; Benoit et al., 1975); such hybrids are generally lowland < 350 m) and particularly common in the north and west of the UK and Ireland (Preston et al., 2002). Hybrids between S. cineraria and S. jacobaea are partially fertile and morphologically variable, most often similar to S. jacobaea (Harper and Wood, 1957; Benoit et al., 1975); such hybrids appear to be spreading in the UK and Ireland either as garden escapes or through spontaneous crossing (Preston et al., 2002). Hybrids between S. jacobaea and S. alpinus are widely distributed in Germany, Tyrol and Switzerland (Hegi, 1929). Generally, the distribution of hybrids in continental Europe is poorly understood; hybrids may have been under-recorded for the parents. The occurrence of hybrids in the introduced range of S. jacobaea is unknown. There appears to have been no investigation of neutral DNA marker variation in either the native or introduced ranges of S. jacobaea.
Physiology and Phenology
In a population of S. jacobaea from Aberdeenshire (Scotland, UK), Forbes (1977) showed that of the plants which flowered in the first two years, or survived into a third year, 8% were annual, 39% were biennial and 53% perennial. Otzen (1977) has suggested that flowering individuals have significant carbohydrate reserves in the stem bases and roots, which may allow S. jacobaea to behave as a facultative perennial.
S. jacobaea contains pyrrolizidine alkaloids (PAs), some of which are highly toxic to animals and humans (Mattocks, 1986). PAs have been described from 459 species in 16 plant families (Rizk, 1991), although only six families contain hepatotoxic PAs (WHO, 1988). The most important families (genera) are: Boraginaceae (Heliotropium), Asteraceae (Senecio) and Fabaceae (Crotalaria). Numerous reviews have been published on the chemistry and toxicology of PAs (e.g., Bull et al., 1968; Mattocks, 1986; Rizk, 1991; Hartmann, 1999). PAs are not toxic to mammals per se, rather the hazard arises through the normal oxidative detoxification mechanisms in the liver that convert them to pyrrolic metabolites (dehydroalkaloids; Mattocks, 1986). Hepatotoxicity or carcinogenicity of these highly reactive electrophilic alkylating agents is a result of their binding to nucleophilic centres in tissues or to cross-link DNA (Mattocks, 1986; Woo et al., 1993; Stegelmeier et al., 1999; Kim et al., 1999; Fu et al., 2001).
Nine PAs are known from the aerial parts of S. jacobaea: jacobine, jacoline, jacocine, jacozine, senecionine, seneciphylline, olosenine, retrosine and senkirkine (Mattocks, 1986; Rizk, 1991;), of which the first six are the most important. It is known that there is considerable plant-to-plant variation in the total PA concentration and concentration of individual PAs (Witte et al., 1992). Herbivory by the adults and larvae of the specialist flea beetle Longitarsus jacobaeae and non-specialist insects, are negatively correlated with PA concentration (Vrieling and van Wijk, 1994; Vrieling and de Boer, 1999). Witte et al. (1992) identified two chemotypes among European populations of S. jacobaea, one the 'jacobine-type' (profile dominated by jacobine, jacoline, jacocine, jacozine, senecionine and seneciphylline) and the other 'erucifoline-type' (dominated by erucifoline, with only traces of PAs from the 'jacobine-type'); these two chemotypes may reflect crossing with S. erucifolius. There appears to be a strong genetic component of variation in PA content between S. jacobaea plants (Vrieling et al., 1993). In an investigation of two annual Senecio species (S. vernalis and S. vulgaris), Hartmann and Zimmer (1986) found that the highest PA content occurred in the capitula, and that PA concentration (1.0-1.4 mg/g fresh weight) was 5- to 10-fold higher than in the roots and leaves. Similar qualitative differences in PA distribution have been shown in S. jacobaea (Witte et al., 1992). There appears to be no significant reduction in the toxicity of S. jacobaea PAs when the leaves are dried (Goeger et al., 1982a; Cooper and Johnson, 1998). In fact, some evidence suggests that dried leaves and plants killed with herbicides are more palatable to livestock (Irvine et al., 1977).
Capitula open when expanding disc florets force the involucral bracts apart; ray florets expand later giving S. jacobaea the initial appearance of being eradiate. Expansion and unrolling of ray florets occurs in less than 24 hours; stigmas are receptive as soon as the floret is expanded. Disc florets open later (centripetally). The capitula are visited by many types of insects, mainly Hymenoptera and Diptera (Cameron, 1935; Harper and Wood, 1957). Flowers produce both nectar and a faint odour, with pollen presentation in the UK between 08.00 and 17.00 h (peak 10.00-12.00 h; Harper and Wood, 1957). Within a single capitulum, anthers continue to dehisce over four to nine days (Harper and Wood, 1957). Rain limits both floret opening and anthesis. Andersson (2001) provides data which indicate that S. jacobaea is self-incompatible; probably with sporophytic self-incompatibility, in common with other members of the Asteraceae (Hiscock, 2000). Thus, S. jacobaea is an example of a successful self-incompatible colonizer (Brennan et al., 2002). In the UK, S. jacobaea is one of the most important species for Lepidoptera (Proctor et al., 1996).
Propagation is primarily by achenes, although vegetative propagation by roots may also occur (Poole and Cairns, 1940; Harper and Wood, 1957). The ray and disc florets of S. jacobaea produce heteromorphic achenes (Green, 1937; McEvoy, 1984). Disc floret achenes are light (mean weight = 199 µg), numerous (mean = 58 achenes per capitula) and equipped with a pappus, which aids wind transport, and rows of trichomes, which may aid animal transport (McEvoy, 1984). In contrast, ray achenes are heavy (mean weight = 286 µg), less numerous (mean = 13 achenes per capitula) and lack apparent dispersal structures (McEvoy, 1984). Disc achenes are released shortly after they mature, the parent may retain ray achenes for months after maturity (Green, 1937; McEvoy, 1984;), due to the latter being retained by the parent plant (Baker-Kratz and Maguire, 1984).
Individual S. jacobaea plants vary greatly in the numbers of achenes that they produce. Cameron (1935) indicates that 4700 to 174,000 achenes are produced per plant, with the higher number being an unusual plant that had been damaged by considerable grazing. Salisbury (1964) cites the example of a plant from the South Downs (UK) that he estimated to have produced c. 170,000. Van der Meijden and van der Waals-Kooi (1979) estimate that up to 30,000 achenes are produced by a single plant. S. jacobaea achene viability has been estimated as high as 80-90%, although lower levels (60%) have been estimated from late-flowering individuals (Salisbury, 1964; Schmidl, 1972; Baker-Kratz and Maguire, 1984). For a given weight, disc achenes have a higher germination percentage than ray achenes; germination time decreases with increasing achene weight in disc achenes, but increases with achene weight in ray achenes (McEvoy, 1984). Crawley and Nachapong (1985) have shown that S. jacobaea plants in the UK, defoliated by Tyria jacobaeae larvae, are capable of producing regrowth shoots that flower and produce achenes in early autumn of the same year. These regrowth achenes are significantly lighter (0.26 mg dry weight versus 0.41 mg dry weight), with a lower germination rate (78.8% versus 86.4%), compared to primary achenes.
In an experimental study, McEvoy and Cox (1987) showed that the majority (89%) of S. jacobaea achenes were dispersed within 5 m of the parent, despite differences arising from the height of release, wind direction, achene type and time of release. In contrast, Begon and Mortimer (1981) speculated that S. jacobaea achenes travel at least 15 m. Disc achenes were dispersed about twice as far as ray achenes (McEvoy and Cox, 1987). Dispersal distances are reduced by high atmospheric humidity due to achene trichomes becoming matted and the phyllaries closing around the achenes (Poole and Cairns, 1940). Animal dispersal of achenes may be important in some cases. For example, large numbers of S. jacobaea achenes are found in rabbit dung in eastern England (Pakeman et al., 1998; Pakeman et al., 1999).
Vegetative reproduction can occur from crown buds, excised root fragments and intact roots (Harper and Wood, 1957; Wardle, 1987). Schmidl (1972) reported that more than 35% of plants produced multiple crowns; disturbance or injury promotes vegetative reproduction. Vegetative rosettes form buds more readily than flowering plants (Poole and Cairns, 1940).
Information on achene longevity is conflicting. Achenes may remain viable for up to 15 years when stored dry. Thompson and Makepeace (1983) showed a decline in achene viability with depth of burial (achene viability declined to 1% in 10-16 years when buried under 4 cm soil). James et al. (2000), in a study to investigate achene longevity in relation to soil type and burial depth, showed that after 16 years, no viable achenes were found in a clay soil, whilst 1-3% of achenes remained viable in silt loam and peat soils, and up to 13% remained viable in sandy soils. Viability was greatest for the most deeply buried achenes (up to 18 years for achenes buried 19-21 cm deep).
S. jacobaea is found in the drier regions of Europe and Asia (Harper and Wood, 1957). It can survive under most soil moisture conditions, even the hot, dry summers of the eastern part of the Pacific Northwest, and overwinters successfully in areas where temperatures reach -30°C when there is good snow cover. However, S. jacobaea tends to be found in more mesic areas. For example, in Australia and New Zealand it is found in high rainfall areas (Schmidl, 1972; Wardle, 1987), whilst in North America, it is established in areas with cool, wet, cloudy weather (Bain, 1991). In Oregon, S. jacobaea appears to be particularly well adapted to coastal areas or to inland areas that have some marine influence and a relatively moderate climate (Hawkes, 1981). Harper and Wood (1957) indicate that severe frost kills the aerial parts of the plant but regeneration can occur from the crown. Poole and Cairns (1940) state that young rosettes regenerating from root fragments are very liable to frost damage. Harper and Wood (1957) indicate that the distribution of S. jacobaea is probably not limited by climatic extremes in Eurasia, and the absence of grazing and cultivation at high altitudes limits distribution. The distribution of S. jacobaea is associated with moderate levels of distrubance and relatively unproductive conditions, although it is not excluded from any vegetation type except where disturbance is minimal (Grime et al., 1988; Clay et al., 2000).
Gange et al. (2002) report that S. jacobaea is weakly mycorrhizal.
Latitude/Altitude RangesTop of page
|Latitude North (°N)||Latitude South (°S)||Altitude Lower (m)||Altitude Upper (m)|
Air TemperatureTop of page
|Parameter||Lower limit||Upper limit|
|Absolute minimum temperature (ºC)||-30|
|Mean annual temperature (ºC)||4||19|
|Mean maximum temperature of hottest month (ºC)||25||45|
|Mean minimum temperature of coldest month (ºC)||-14||8|
RainfallTop of page
|Parameter||Lower limit||Upper limit||Description|
|Dry season duration||0||7||number of consecutive months with <40 mm rainfall|
|Mean annual rainfall||40||0||mm; lower/upper limits|
Rainfall RegimeTop of page
Soil TolerancesTop of page
Special soil tolerances
Natural enemiesTop of page
|Natural enemy||Type||Life stages||Specificity||References||Biological control in||Biological control on|
|Botanophila jacobaeae||Herbivore||Fruits|pods; Plants|Inflorescence|
|Botanophila seneciella||Herbivore||Fruits|pods; Plants|Inflorescence|
|Cochylis atricapitana||Herbivore||Plants|Growing point|
|Coleosporium tussilaginis f.sp. senecionis-sylvati||Pathogen||Fruits|pods; Plants|Growing point; Plants|Inflorescence; Plants|Leaves; Plants|Stems|
|Longitarsus flavicornis||Herbivore||Plants|Growing point; Plants|Inflorescence; Plants|Leaves; Plants|Roots; Plants|Stems|
|Longitarsus jacobaeae||Herbivore||Plants|Growing point; Plants|Inflorescence; Plants|Leaves; Plants|Roots; Plants|Stems|
|Puccinia dioicae||Pathogen||Plants|Growing point; Plants|Inflorescence; Plants|Leaves; Plants|Stems|
|Tyria jacobaeae||Herbivore||Plants|Growing point; Plants|Inflorescence; Plants|Leaves; Plants|Stems|
Notes on Natural EnemiesTop of page
Means of Movement and DispersalTop of page
Achenes are wind-dispersed (perhaps poorly so; Wardle, 1987), although Poole and Cairns (1940) estimated that only about 0.5% of achenes were wind-dispersed. Achene dispersal distances range from 0 m to 14 m depending on conditions (McEvoy and Cox, 1987). The majority of achenes (89%) are dispersed within 5 m of the parent plant, and in no cases were achenes found to disperse more than 14 m from the parent plant. Schmidl (1972) indicates that achenes may be dispersed by water. McEvoy and Rudd (1993) have shown that disturbance is a major factor in establishment of S. jacobaea and populations are limited more by the availability of microsites for germination and establishment than by achene availability.
Vector Transmission (Biotic)
Humans and their animals transport achenes (Schmidl, 1972).
Movement of hay is likely to spread the achenes, whilst set-aside creates ideal habitats for S. jacobaea establishment in the UK (Clay et al., 2000). The movement of livestock, and survival of achenes in faeces, is also likely to aid dispersal. Poor management of pasture provides ideal conditions for the establishment of S. jacobaea.
S. jacobaea may be accidentally introduced by man, collecting the plants for ornament and then disposing on rubbish heaps; also as a result of movement of soil in the course of building works, and by attachment to vehicles or in the slip-stream of road and rail vehicles.
Intentional introduction of S. jacobaea is unlikely, although there is an anecdotal account of inflorescences being offered for sale by enterprising UK farmers (Page, 1993).
Pathway VectorsTop of page
Plant TradeTop of page
|Plant parts liable to carry the pest in trade/transport||Pest stages||Borne internally||Borne externally||Visibility of pest or symptoms|
|Fruits (inc. pods)||weeds/fruits|
|Growing medium accompanying plants||weeds/fruits|
|Stems (above ground)/Shoots/Trunks/Branches||weeds/fruits|
|Plant parts not known to carry the pest in trade/transport|
|True seeds (inc. grain)|
Impact SummaryTop of page
|Fisheries / aquaculture||None|
ImpactTop of page
S. jacobaea is primarily hepatotoxic (with renal megalocytosis and mild nephrosis) in animals, although it appears to be pneumotoxic in pigs (Harding et al., 1964; Bull et al., 1968). Livestock and equines differ widely in their sensitivity to PAs (WHO, 1988), sheep and goats (chronic lethal dose of S. jacobaea = 1.25-4.04 kg/kg body weight) are resistant, cattle and horses (chronic lethal dose = 0.05-0.2 kg/kg body weight) less so, and poultry and pigs, rather sensitive (Hooper, 1978). The resistance of sheep to PA poisoning has been ascribed to destruction of the alkaloids in the rumen by conversion into non-toxic 1-methylenepyrrolizidine derivatives (Bull et al., 1968; Craig et al., 1986). S. jacobaea toxicity remains in hay and dried grass and is reduced in silage, but not enough to be safe for consumption by cattle (Candrian et al., 1986); dried grass, hay or silage is the most common source of livestock poisoning (Giles, 1983; Leyland, 1985). In Oregon, Coombs et al. (1996) estimate that PA poisoning of livestock decreased by about 90% when S. jacobaea populations were controlled.
Environmental ImpactTop of page
Impact: BiodiversityTop of page
Social ImpactTop of page
PAs and/or toxic metabolites are secreted in the milk of lactating dairy cattle (Dickinson et al., 1976; Dickinson and King, 1978; Goeger et al., 1979; Deinzer et al., 1982; Goeger et al., 1982b; Molyneaux and James, 1990) and have been found in eggs (Edgar and Smith, 1999). However, since commercial milk supplies are bulked there is unlikely to be significant human exposure by this route (ANZFA, 2001), although S. jacobaea consumption rapidly reduces butterfat production in cattle (Miller, 1936). During PA poisoning epidemics, cases of veno-occlusive disease in suckling babies have been recorded (Roulet et al., 1988). PAs can been found in honey (Dickinson, 1976; Deinzer et al., 1977; Röder, 1995; Crews et al., 1997; Edgar et al., 2002). PA levels, at least as high as 3.9 µg/g honey, have been recorded from S. jacobaea honey, although such honey is not used commercially as it has an unpleasant flavour (Deinzer et al., 1977; Crews et al., 1997). However, the consequences of low level PA exposure for human health are unclear (ANZFA, 2001).
Risk and Impact FactorsTop of page
- Invasive in its native range
- Proved invasive outside its native range
- Highly adaptable to different environments
- Tolerates, or benefits from, cultivation, browsing pressure, mutilation, fire etc
- Highly mobile locally
- Has high reproductive potential
- Has propagules that can remain viable for more than one year
- Negatively impacts agriculture
- Negatively impacts animal health
- Negatively impacts tourism
- Reduced amenity values
- Reduced native biodiversity
- Competition - monopolizing resources
- Highly likely to be transported internationally accidentally
- Difficult to identify/detect as a commodity contaminant
- Difficult to identify/detect in the field
- Difficult/costly to control
UsesTop of page
S. jacobaea is an important food plant for many wild insect species in its native range. For example, Smith (1980) indicates that 84 insect species depend on S. jacobaea, including 33 lepidopterans. Furthermore, Wiggins (1977) reported that in a survey of Sussex (UK) wild flowers, S. jacobaea received more visits by insects than any other species. S. jacobaea is also an important species for insects in its introduced range (Frick, 1964; Frick and Hawkes, 1970; Frick, 1972).
Despite PA toxicity, S. jacobaea has been recommended for medicines (e.g. Gerard, 1597; Grieve, 1931; Schoental, 1963; Wren, 1968) and continues to be used in homeopathic preparations.
Anecdotal reports indicate that enterprising farmers may sell S. jacobaea as cut flowers to an unsuspecting public (Page, 1993).
Similarities to Other Species/ConditionsTop of page
In North America, based on the size of the plant, S. jacobaea may be confused with S. eremophilus and Tanacetum vulgare. S. jacobaea and S. eremophilus are distinguished by leaf morphology; leaves of S. eremophilus taper to a point and are once partite, whilst those of S. jacobaea are rounded and 2-3 partite. The homomorphic, discoid capitula, dark-margined phyllaries and strongly aromatic leaves of T. vulgare distinguish it from S. jacobaea.
In New Zealand, S. jacobaea may be confused with another exotic, S. aquaticus.
Prevention and ControlTop of page
Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.Cultural Control
Sheep will graze S. jacobaea at both the rosette and the flowering stages. Grazing at the rosette stage can weaken the plant and delay flowering, whilst at the flowering stage it can prevent achene production. Sheep show a high tolerance of pyrrolizidine alkaloids, particularly older sheep, and have been suggested as a means of controlling S. jacobaea (Brenchley, 1920; Sharrow and Mosher, 1982; Amor et al., 1983; Olson and Lacey, 1994; Betteridge et al., 2000). Heavy stocking is normally necessary to ensure that at least the larger rosettes and the flowering plants are grazed. However, continuous exposure of sheep to dense ragwort infestations should be avoided as toxicity problems can occur, particularly in areas known to have a high copper content in the soil (WHO, 1988). Following grazing, ragwort plants may recover quickly and produce new shoots. A second crop of flowers may be produced following grazing at the flowering stage, which will necessitate a further grazing if achene production is to be prevented. Sheep-based control of S. jacobaea cannot be recommended on animal welfare grounds.
Pasture improvement is as an essential adjunct to any control programme. Maintenance of a dense vigorous pasture will reduce the opportunity for S. jacobaea seedlings to establish and help to prevent the spread of S. jacobaea. Cropping pastures infested with S. jacobaea is one of the most effective ways of reducing the infestation. Repeated cultivation destroys the established plants and exhausts the achene banks in the soil.
Alternative land uses may be considered in cases of heavy infestations. Establishing trees for forestry or amenity purposes may provide an effective way of suppressing S. jacobaea as has been suggested in Tasmania, Australia (DPIWE, 1998). Such cultural control is a long-term intervention, therefore interim control measures are still essential.
Mechanical approaches to S. jacobaea control include cutting, digging-out, hand-pulling and machine-pulling; each of these treatments may need to be repeated two or three times per year (preferably before flowering). Cutting is a useful emergency treatment to prevent fruiting, although the plants must be cut before the achenes are mature and the treatment must be followed by another control treatment, since cutting may encourage production of side shoots. For pulling to be effective, the crown, together with the larger roots, must be completely removed from the ground or rapid regrowth may occur. Regrowth from the small roots that would normally be left after pulling or grubbing is also possible. Digging-out and hand-pulling (using gloves) are best accomplished when the soil is wet but are not practical for large areas of S. jacobaea infestation. A problem of both digging-out and hand-pulling control methods are that small plants may be missed, hence the need for annual treatment. Machine-pulling is suitable for large areas of infestation; plants are selected based on height differences; however, shorter plants are ignored. Plants must be removed from the site, as there is evidence that once removed from the soil, they show increased palatability to livestock, and burnt to prevent achene production.
Many different herbicides, types of application methods and times of application have been tested in the UK, North America, Australia and New Zealand for the control of S. jacobaea. An important part of such investigations is the effect of the herbicide treatment on useful species in the pasture sward (such as Trifolium and Lolium species).
Black (1976) showed that 2,4-D ester gave effective control of S. jacobaea in the late-rosette, bud and flowering stages, although repeated treatments were necessary. 2,4-D was superior to 2,4-DB at equivalent rates. 2,4-DB ester effectively controlled seedling and early-rosette S. jacobaea only. Furthermore, the herbicides mecoprop, 2,3,6-TBA, 2,4-D acid and fenoprop were as effective as 2,4-D ester for the control of S. jacobaea but caused more injury to other sward components. Thompson (1977) showed that granular application of picloram gave effective S. jacobaea control, followed by chlorthiamid, dichlobenil, 2,4-D and dicamba. Lawson and Wiseman (1982) found that clopyralid in a gel, applied in the spring, killed S. jacobaea. Rahman et al. (1990) showed that a combination of 2,4-D and phosphate fertilizer resulted in the best sward composition and growth, and allowed the least re-invasion of ragwort into low fertility hill country pasture. Friend (1987) showed that for complete prevention of achene production it was necessary to use a mixture of diquat and clopyralid or 2,4-D. Dixon and Clay (2001) showed that weed wiper applications of glyphosate and clopyralid applied in both May and June and glyphosate applied as a conventional spray in June (in the UK) killed all plants, whilst clopyralid appeared to reduce the number of plants germinating the following year. Dixon and Clay (2001) also showed that citronella oil (Cymbopogon winterianus) had a more rapid effect than either clopyralid or 2,4-D, especially when applied to smaller plants in March. Treatment of S. jacobaea with 2,4-D appears to mobilize carbohydrates and may make the plant more palatable to livestock (Irvine et al., 1977).
Bird (1977) demonstrated that a boom spray application of 2,4-D ester gave only 40% control of S. jacobaea, whereas a boom spray application combined with two spot sprays of picloram in September and November in New Zealand gave about 95% control. Thompson (1977) showed that as a foliar spray, asulam was less effective than any granular herbicide application, except dicamba. Spot applications of granules of picloram or dicamba completely killed old plants (Taylor, 1973). Martin et al. (1988) in trials in New Zealand showed that spot treatments of picloram with 2,4-D provided >95% control, regardless of application time. James et al. (1997) showed that spot treatment of flazasulfuron resulted in excellent weed control and avoided the problem of pasture damage. Friend (1987) reported that clopyralid, applied as a spot spray, at the late rosette and shooting stages completely prevented achene production and gave a very high level of mortality.
Time of application
Forbes (1978) showed that October spraying with 2,4-D amine MCPA gave 99% control of S. jacobaea in Scotland. In Northern Ireland, Courtney (1975) reported that MCPA and 2,4-D gave 100% selective control in grassland when applied in spring. Herbicides may be applied over a wide range of dates between April and November, although spraying after the early bud stage may allow achenes to be produced. Forbes (1974) showed that MCPA, applied at the rosette stage in mid-May prevented flowering in the year of spraying. However, 2,4-D ester controlled both flowering and first year plants in the year of spraying better than MCPA. Friend (1987) found that no achenes were produced when plants were sprayed with clopyralid before the appearance of the first flowers, although achene weight and germinability increased when spraying was delayed until after flowering. In Australia, there is evidence that regrowth and flowering may occur in 2,4-D-treated plants but the achenes are infertile (Watt, 1987).
Effect on other pasture species
Black (1976) showed grasses and white clover were increasingly injured as 2,4-D ester application increased. Taylor (1973) showed that overall application of herbicides frequently resulted in severe damage to white clover (Trifolium repens). James et al. (1997) achieved very good weed control with flazasulfuron but also damage to the pasture, particularly Lolium perenne.
In general, 2,4-D is a successful control agent, although a second application is often needed for adequate control and older plants need higher doses than generally recommended. In the UK, spraying as late as December increased subsequent germination and establishment of seedlings compared with an April application, although this would not be a problem for annual herbicide application (Forbes, 1978). DEFRA (2002) recommend herbicide applications (2,4-D or citronella oil for selective control and glyphosate for non-selective control) when rosettes start growing or in early summer before flower heads mature, using either spot-treatment, a wick applicator or spraying with a selective herbicide. In any of these cases, herbicide may need to be applied twice per year, every two years. Other recommendations for chemical control of S. jacobaea in parts of its introduced range can be found (e.g., DPIWE, 1998).
Biological control is effective in reducing plant density and is recommended for areas where other controls are neither practical nor economical. Several years are required to establish an insect population large enough to reduce a weed population. The objective is not to eradicate S. jacobaea but to reduce it to a level where it has negligible economic effects. The three most frequently introduced insects for biological control are Tyria jacobaeae (cinnabar moth), Longitarsus jacobaeae (ragwort flea beetle) and Botanophila seneciella (ragwort seed fly). T. jacobaeae larvae feed on the aerial parts of S. jacobaea (Dempster, 1982; James et al., 1992). B. seneciella larvae penetrate the achene heads and feed on the developing achenes, usually attacking up to 40% of the heads and consuming 75-95% of the achenes (McEvoy et al., 1991); uneaten achenes often fail to germinate. L. jacobaeae larvae feed on the root crowns, stems and leaf petioles of the plants, whilst adults attack the leaves (Frick, 1970; Hawkes and Johnson, 1978; Windig, 1991).
Reviews of biological control strategies for S. jacobaea have been prepared for its introduced distribution, particularly for North America (e.g., McEvoy et al., 1991), Australia (e.g., McLaren et al., 2000) and New Zealand (e.g., Syrett, 1983). The success of such strategies have been mixed, for example, they have been very valuable in controlling S. jacobaea in California and Oregon ( Pemberton and Turner, 1990; McEvoy et al., 1991), Canada (Harris et al., 1979) and Tasmania (McLaren et al., 2000) but, to date, have proven less useful in New Zealand (Ivens, 1979; Syrett et al., 1991). Biological control does not appear to be an effective strategy for S. jacobaea control in the UK (Clay et al., 2000).
S. jacobaea was brought under successful biological control in California through the combined action of T. jacobaeae and L. jacobaeae, which persist despite very low S. jacobaea densities (Pemberton and Turner, 1990). The control of S. jacobaea has resulted in the return of nearly natural vegetation on coastal prairie sites and improved productivity on pasture sites (Pemberton and Turner, 1990). T. jacobaeae was released in western parts of North America during 1959-1962 for S. jacobaea control (Nagel and Isaacson, 1974) and together with additional releases of T. jacobaeae, L. jacobaeae and B. seneciella in western Oregon in 1975, has resulted in the reduction of S. jacobaea infestations by 60-70% (Brown, 1990).
T. jacobaeae and L. jacobaeae are complementary enemies of S. jacobaea and feed on different stages and at different times of the year (Crawley and Pattrasudhi, 1988), and have proved an effective biocontrol strategy in North America, although in coastal areas of North America, L. jacobaeae appears to be the main control factor (e.g. Harris et al., 1981; Hawkes, 1981; McEvoy et al., 1991; Syrett et al., 1991; James et al., 1992). Ireson et al. (2000) showed that Longitarsus flavicornis was dispersed over all infested areas of southern Tasmania, and more than 90% of northern Tasmania. However, prevailing site conditions (e.g. flooding) and incompatible management practices (e.g. boom-sprayed herbicides) restrict the efficacy of L. flavicornis on many areas of Tasmania. Recently, the lepidopteran Cochylis atricapitana, the larvae of which are leaf, crown, stem or bud borers, has been effective in controlling S. jacobaea in Australia (McLaren, 1992; McLaren, 2000), especially where T. jacobaeae and B. jacobaeae have not proven particularly effective (Field, 1990; Syrett, 1990).
Much research has been undertaken into the biological relationships between S. jacobaea and its insect pests in both its native (e.g., Islam and Crawley, 1983; Crawley and Nachapong, 1984; Wilcox and Crawley, 1988; Crawley and Gillman, 1989; Gillman and Crawley, 1990) and introduced ranges (e.g., McEvoy et al., 1991; McEvoy et al., 1993; McEvoy and Rudd, 1993; McEvoy and Coombs, 1999).
Thousands of pages on the Web are devoted to S. jacobaea control, particularly in North America, Australia and New Zealand. These pages, and particularly those of Government agencies, should be consulted for the most recent recommendations regarding S. jacobaea control. In addition, Government agencies have produced information leaflets on the control of S. jacobaea where it is, or is likely to become, a problem (e.g., Northland Regional Council, undated; Mather, undated; MAFF, undated). Integrated management requires containment, reduction and finally elimination of S. jacobaea. Such long-term control has a short-term goal of preventing achene production in infested areas, and is emphasized by all control recommendations. In general, S. jacobaea occurrence in pastures is a symptom of poor management, therefore reseeding and grazing and fertility management may be essential components of a control plan. Furthermore, if management is to be effective in pastures, control must also take place on wasteland, set-aside and roadsides (DEFRA, 2002). Woo et al. (2001) discuss the integrated management of S. jacobaea.
ReferencesTop of page
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