S. inaequidens can grow under temperate and Mediterranean climates. It is opportunistic and has the ability to colonise a wide range of habitats including the following vegetation zones: temperate deciduous forests, temperate steppes and Mediterranean sclerophyllous forests and sclerophyllous shrubs (EPPO 2006b). In Italy S. inaequidens spreads along roads and torrents and up to altitudes of 1420 meters (Brandes 1999). It reaches the highest cover at well drained places lying in the full sun with a vegetation cover of between 20 and 85 percent (Brandes 1999). The species even invades in montane pastures and montan (subalpine) ruderal vegetation (Brandes 1999). In other parts of its range it has been observed from coastal areas up to 1900 m altitude (EPPO 2006b). It is also found in natural environments such as dunes and cliffs in littoral areas, and temporary ponds in France (Brunel 2003, in EPPO 2006b). Unusual habitats include lawns and the facade of the cathedral at Cologne, Germany (Heger & Böhmer 2006).
S. inaequidens colonises open and disturbed lands, wastelands, fallows, railway tracks, roadsides, crops (vineyards), burnt land and pastures (EPPO 2006b). In Central Europe S. inaequidens spreads rapidly along motorways and railroad tracks and grows predominantly in ruderal habitats and occasionally old fields in early successional stages (Bossdorf et al 2008). In Europe S. inaequidens grows on warm and dry ruderal sites and is often found associated with railroads and gravel areas, highways, river ports, logging areas, industrial sites, disused quarries, storm-damaged forests and on flat roofs or in flower tubs. It also occurs on natural sites such as in volcanic soils, on rocky sites (in the central Rhine valley, Germany) and in coastal dunes of Belgium and Germany (Heger & Böhmer 2006).
Disturbance has been shown to enhance invasion (Hobbs & Huenneke 1992, in Cano & Sans 2007) by supplying aliens with new resources, as a consequence of the decline in the use of the resources by native vegetation. Garcia-Serrano and colleagues (2004) also found that shrubs facilitated the recruitment of S. inaequidens; the presence of open shrublands can be a driving force for the invasion processes of introduced species in Mediterranean communities (Cano & Sans 2007). Shrubland was the habitat that most favoured recruitment in natural conditions, however, grassland was the most suitable habitat in the short term (Cano & Sans 2007). Severe disturbances such as fires could also occur in forests and allow the invasion of grass and shrub lands (Cano & Sans 2007).
Mean annual rainfall ranges from 500 to 1000 mm. Mean annual temperature ranges from 10 deg;C to 20 deg;C. Mean maximum temperatures are 30 deg;C to 35 deg;C. Mean minimum temperatures are minus 5 to 0 deg;C. The absolute minimum temperature is minus 15 deg;C (EPPO 2006b).
Principal source: Heger, T. and Böhmer, H.J., 2006: NOBANIS – Invasive Alien Species Fact Sheet – Senecio inaequidens. – From: Online Database of the North European and Baltic Network on Invasive Alien Species – NOBANIS
European and Mediterranean Plant Protection Organization (EPPO). 2006b. Data sheet on Invasive Plants Senecio inaequidens
Compiler: Interim profile: IUCN SSC Invasive Species Specialist Group (ISSG) with support from the EU-funded South Atlantic Invasive Species project, coordinated by the Royal Society for the Protection of Birds (RSPB)
Updates with support from the Overseas Territories Environmental Programme (OTEP) project XOT603, a joint project with the Cayman Islands Government - Department of Environment
Review:
Publication date: 2010-10-04
Recommended citation: Global Invasive Species Database (2024) Species profile: Senecio inaequidens. Downloaded from http://www.iucngisd.org/gisd/speciesname/Senecio+inaequidens on 07-10-2024.
Large quantities of Senecio species ingested by livestock over a short period of time induce acute poisoning which leads to death. A large single non-lethal dose or multiple lower doses ingested over a longer period may cause chronic diseases including anorexia, diarrhoea and nervous system symptoms including incoordination of the hind limbs, circling, apparent blindness and tremors (Dimande et al. 2007).
Invasive plants are capable of modifying ecosystem function. In a study by Dassonville and colleagues (2008) the impacts of highly invasive plant species, including Senecio inaequidens, on nutrient pools in the topsoil and the standing biomass was tested. Invaded plots had increased above-ground biomass and nutrient stocks in standing biomass compared to un-invaded vegetation. Enhanced nutrient uptake may be a key trait of highly invasive plant species.
German experts agree that S. inaequidens does not demonstrably pose a threat to indigenous species or plant communities at present as the plant rather appears to fill vacant ecological niches in Europe. It has not been investigated whether the species puts indigenous species at risk near natural sites but it has been observed that S. inaequidens forms dominant populations on rocky sites (Adolphi & Klingenstein Pers. Comm., in Heger & Böhmer 2006). It is impossible to exclude a threat to indigenous plant species of great importance to nature conservation (eg: blue lettuce Lactuca perennis). Its colonisation success on open rocky sites may pose a risk to endangered animal species (eg: Saltatoria - a division of Orthoptera including grasshoppers, locusts, and crickets). In coastal dunes it occurs especially in yellow dunes with marram grass (Ammophila arenaria) and in sea-buckthorn scrub (Hippophae rhamnoides) where it changes the floristic composition of the dune vegetation (Isermann Pers. Comm., in Heger & Böhmer 2006). In the French Mediterranean area it is reportedly a threat to native Centaurea corymbosa (Brunel 2003, in EPPO 2006b).
S. inaequidens is a cereal crop weed and in South Africa may find its way into bread causing toxicity in consumers and perhaps even death (Bromilow 1995, in Heger & Böhmer 2006). S. inaequidens toxins may also be detected in the milk of cattle which feed on the plant, although it is usually avoided by grazing animals. In France S. inaequidenscan be found in vineyards and pastures and in Denmark the species has been found in apple tree orchards (Skovgaard Pers. Comm., in Heger & Böhmer 2006).
Because narrow-leaved ragweed is not susceptible to the most commonly used herbicide, glyphosphate, this plant causes additional annual expenditures of 100,000 Euros for control measures along railroad tracks in Germany (Reinhardt & Streit 2003).
Climate change can be considered to have favoured the invasion of S. inaequidens in Europe and the plant's ability to reproduce may increase considerably with the gradual warming of the climate (Heger & Böhmer 2006).
Monitoring: The identification of critical mechanisms that favour invasion is useful for local managers. One of the main outcomes of a Mediterranean study by Cano & Sans (2007) was to recommend a survey of open shrublands and grasslands during rainfall periods. A monitoring program is advisable in areas where S. inaequidens has either begun to exert massive colonisation pressure on locations outside of the ruderal sites preferred in the past or is capable of doing so (eg: in cereal cultures). A monitoring program should focus on expulsion mechanisms between S. inaequidens and thermophilous native species with poor competitive capacity, as well as on the potential impacts to agriculture and human health in terms of toxic contamination of produce (see General Impacts) (Heger & Böhmer 2006).
\nField management: Reducing the risk of fire, avoiding overgrazing and sowing with perennial species with good ground cover such as Trifolium spp. are likely to limit the spread of S. inaequidens (Brunel 2003, in EPPO 2006b). From a management perspective it is clear that disturbance increases invisibility in all habitat types. Therefore disturbance should be reduced in natural ecosystems to minimize invasion by S. inaequidens (Garcia-Serrano & Sans 2004).
Manual control: Hand-pulling or mowing before flowering repeated for several years has proven to be effective in some natural areas of the South of France (EPPO 2006b). However, other sources claim S. inaequidens is resistant and even promoted by mowing (Radkowitsch Pers. Comm., Werner Pers. Comm., in Heger & Böhmer 2006). Non-specific control measures such as mowing may actually provide a competitive advantage for S. inaequidens over other ruderal plants (cf. also Guillerm et al. 1990, in Heger & Böhmer 2006). If using such a method monitoring and control must be carried out over several years to remove the seed bank. Hand-pulling is at best a method for small areas of establishement. Eradication has been achieved in Corsica in this way. It is essential to collect and destroy the plants which have been pulled out as they can still produce achenes (a type of dry fruit propagule) for two or three days following removal (EPPO 2006b).
\nChemical control: It has been observed that this species is exceptionally resistant to herbicides (Hard Pers. Comm., in Heger & Böhmer 2006). In vineyards, treatment with low toxicity phytosanitary products has proved effective in the South of France (EPPO 2006b).
\nBiological control: The aphid Aphis jacobaeae is associated with the European native Senecio. jacobaea and has been observed to attack S. inaequidens in France (Fort et al. 2003, in EPPO 2006b). The beetle Longitarsus jacobaeae (cf. Scherber et al. 2003, in Heger & Böhmer 2006) is another proposed biological control agent; the adults of these beetles accept S. inaequidens for feeding and mating (Scherber et al, 2003). However biological control may not be easy to apply in practice or may only be applicable for small areas (cf. EPPO 2004, in Heger & Böhmer 2006).