Flowers are inflorescences (capitula), and are yellow and 5-6mm in diameter. Capitula are borne on stalks at the end of branches. Flowers open from 6am to 11am. The fruit is an achene that is 2.5-4mm long and 1mm wide, compressed and obovoid in shape (Pethybridge, 2005). Achenes have 3-5 ribs and are rugose in texture. Mature seeds have a white feathery pappus (5-8mm long), that collectively form a white puff ball similar to dandelion (Virginia Tech, Undated). A single plant can produce over 8,000 seeds (Chauhan et al., 2005) that are wind dispersed.
Other uses include food for poultry, rabbits and fodder for cattle (Grubben & Denton, 2004). It has potential to be used as a trap crop for control of insect populations (Grubben & Denton, 2004).
Principal source:
Compiler: 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: 2010-07-23
Recommended citation: Global Invasive Species Database (2024) Species profile: Sonchus oleraceus. Downloaded from http://iucngisd.org/gisd/speciesname/Sonchus+oleraceus on 31-08-2024.
S. oleraceus is also an important alternative host of pests and diseases of crops (CSIRO, 2007). It is a known host of a wide range of viral diseases including watermelon mosaic virus (WMV), pepino mosaic virus (PepMV), tomato spotted wilt virus (TSWV) and alfalfa mosaic virus (AMV). It is the host for the economically significant castor whitefly (Trialeurodes ricini), Bemisia whiteflies, cotton bollworm (Helicoverpa armigera and the nematode Radopholus similis (Grubben & Denton, 2004). It is also likely to be an important host for downy mildew (Bremia lactucae), one of the worst diseases of lettuce which is an important vegetable crop worldwide (Vieira & Barreto, 2006).
Grazing: Grazing of Sonchus spp. by cattle and sheep effectively suppresses infestations in pastures, and weakens plants allowing other control methods to be more effectively used (Zollinger & Parker, 1999 in Guertin, 2003). They also make excellent feed for livestock.\r\n
Chemical Control: For control of Sonchus spp. (asper and oleraceus), a pre-emergent herbicide containing isoxaben can be used, herbicidal soaps when the plants are young, or glyphosate when plants are mature. Zollinger and Parker (1999 in Guertin, 2003) recommend 2,4-D, clopyralid, dicamba, glyphosate, and picloram for control of Sonchus spp., while Rice (1992 in Guertin, 2003) 2,4-D, DCPA, diethatyl-ethyl, MCPA, amitrole, atrazine, bromoxynil, chlorsulfuron, dicamba, dichlorprop & 2,4-D, diuron, glyphosate, isoxaben (Snapshot), norflurazon, oryzalin, oxyfluorfen, paraquat, Ornamental Herbicide II, napropamide, simazine and tebuthiuron.\r\n
Sonchus oleraceus has developed resistance to chlorsulfuron in southern Queensland and northern New South Wales (Adkins et al. 1997 in Chauhan et al. 2006) atrazine (CSIRO, 2007), and all lettuce (Lactuca sativa) herbicides (University of California Riverside, Undated in Guertin, 2003). A recent study carried out in California also found methyl bromide and alternative fumigants to be ineffective against S. oleraceus (Shrestha et al., 2009). Apparently spot spraying of Lontrel® 10ml/10L with a wetting agent can be used to control the plant, preferably at the rosette stage (FloraBase, 2010).\r\n
Biological Control: Biological agents are currently being researched as a possibility for managing S. oleraceus and other Sonchus species in Australia (CSIRO, 2007). Sonchus species have previously been the target of biological control in Canada (Peschekn, 1984 in CSIRO, 2007). Preliminary surveys for biological control agents have been made in southern France and northern Europe (Scott & Jourdan, 2005; Peschken, 1984). Currently the rust fungus Miyagia pseudosphaeria and an unidentified eriophyid mite species are two widespread organisms in Australia with potential for control. The CSIRO project will focus on determining the impact of these potential control agents on related native Australian species ( Sonchus hydrophilus and Actites megalocarp and on weedy S. oleraceus and S. asper (CSIRO, 2007).