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Taxonomic name: Brassica tournefortii Gouan Synonyms: Brassica tournefortii var. sisymbrioides (Fisch.) Grossh. Common names: African mustard, Asian mustard, Aslooz (Libya), Mediterranean turnip, Sahara mustard, Tournefort's birdrape, wild turnip Organism type: herb Brassica tournefortii, commonly known as Sahara mustard, is an annual herb that is especially common in areas with wind-blown sediments and disturbed sites such as roadsides and abandoned fields. It appears to suppress native wildflowers by monopolising available soil moisture as it builds canopy and matures seed long before many native species have begun to flower. B. tournefortii also increases fuel loads and fire hazard in desert scrub and coastal sage scrub. There is very little information regarding the control of this species. It is reported that managing for dense stands of native grasses will assist in eradicating this species from areas, but there are no documented mechanical and biological controls that are successful in managing this species. Description Brassica tournefortii is described as an annual herb with stems 10 to 100cm tall. The plants flower early; the small, dull yellow flowers are inconspicuous compared to most other true mustards. Petals are less than 5 to 7mm. Individual flower stalks are longer than the sepals and spread away from the stem. Fruits have an obvious beak at the tip. The pedicels of the fruits are 4 to 10mm long and diverge stiffly from the stem at a forty-five degree angle (Sanders and Minnich, 2000). B. tournefortii shows variability in size depending on the availability of soil moisture. Drought-stressed plants can reproduce with leaves as small as 8cm long and on sandy soils with sufficient moisture leaves have known to grow to more than 50cm long, giving the plant a 1m spread, making it the largest herbaceous rosette plant in the region (Van Devender et al. 1997). Occurs in: desert, range/grasslands, ruderal/disturbed Habitat description Sanders and Minnich (2000) report that, "Brassica tournefortii is especially common in areas with wind-blown sediments. This species is also invading exotic annual grassland and coastal sage scrub. It often forms almost pure stands on abandoned sandy fields. The authors also state that B. tournefortii is most common in disturbed sites such as roadsides and abandoned fields, and that it can be found, but is scarce, on alluvial fans and rocky hill slopes." The Mojave Weed Management Area (UNDATED) states that, "B. tournefortii is especially common in sandy lowland habitats across the Sonoran Desert, including low dunes, interdune troughs, sandy flats, and sandy-gravelly washes." Brooks and Pyke (2002) in their study of the role of invasive plants and fire in the deserts of North America describe the invasion sequence of species in the deserts of N. America. They explain that new populations of invasives go through a very slow initial lag phase. They are restricted to sites with relativly high nutrient and water levels until they reach a 'critical mass' and take advantage of years when there is high rainfall. The authors state that this sequence was demonstrated by B. tournefortii in the Sonoran desert during the 1960s to 1970s and in the Mojave desert during 1980s to 1990s. General impacts Sanders and Minnich (2000) report that, "Dense stands of B. tournefortii appear to suppress native wildflowers. Because of its early phenology, it appears to monopolise available soil moisture as it builds canopy and matures seed long before many native species have begun to flower. This species also locally dominates exotic grasslands in dry, open sites, especially disturbed areas. It expands over larger areas when drought suppresses other exotic annuals such as Bromus rubens, Avena fatua, Brassica geniculata, and Erodium cicutarium. B. tournefortii increases fuel loads and fire hazard in desert scrub and coastal sage scrub. It also establishes from a soil seed bank after fire." Van Devender et al. (1997) identify B. tournefortii as one of six weeds (the other five being grasses: Bromus madritensis ssp. rubens, Pennisetum ciliare, P. setaceum, Schismus arabicus, and S. barbatus) that have the potential to cause the most ecological damage in the Sonoran Desert Region. B. tournefortii is especially common in sandy lowland habitats across the Sonoran Desert, including low dunes, interdune troughs, sandy flats, and sandy-gravelly washes. Uses The Plants For A Future Database (1997) states that the leaves of Brassica tournefortii can be used to create various oils. The authors state that the leaves and young shoots can be cooked, and edible oil can be obtained from the seed. Dr. Khaled O. Abukhabta (pers. com. 2005) reports from Libya that it is widely used as food, mixed with kuskus (couscous) and some other spices to give it a very good flavour. He adds that in addition to it's laxative effect (high content of fibers), it contains 3-methylsulfinylpropyl glucosinolate, which reduces the risk of cancer of the lung, stomach, colon and rectum, with a possible reduction in endometrial and ovarian cancer and a decrease in total cancer incidence. Geographical range Native range: Africa, Asia, and Europe (USDA-GRIN, 2003) Known introduced range: Australia, and North America (Adkins et al. 1997, and USDA-NRCS 200) Introduction pathways to new locations Agriculture: Sanders and Minnich (2000) report that, "Brassica tournefortii probably was introduced with date palms brought from the Middle East in the early part of this century with the development of the date industry in the Coachella Valley." Local dispersal methods On animals: Sanders and Minnich (2000) report that, "During rains, a sticky gel forms over the seed case that permits seeds to disperse long distances by adhering to animals." Management information Mechanical: The spread of B. tournefortii can be reduced by controlling it along roads, which provide corridors for rapid invasion into new habitats. In small areas Sahara mustard can be eradicated by pulling plants before they mature seed. This is most effective in new invasions where a seed bank has not been established (Invaders of the Sonoran Desert Region, Undated). Sanders and Minnich (2000) report that, "Hand pulling of B. tournefortii might be effective in limited areas when seed pools have been suppressed. Planned burns may not be a useful option. Although fires cause high seed loss, stem densities reach pre-burn levels within one or two growing seasons. Partial seed survival after fire may be related to its hard seed coat. B. tournefortii is closely related to a number of important vegetable crops, so it will be difficult to find an agent that will attack this plant but not damage food crops. Even the possibility of transfer of a control agent to a valuable food crop may create political pressures that could prevent importation of the agent. Since B. tournefortii establishes from a seed bank, it is doubtful that grazing could suppress the spread of this annual. The establishment of dense cover of exotic annual grasses apparently suppresses this species." Chemical: In selected areas herbicide treatment may be effective. Sahara mustard tends to be the first annual to germinate after a rain, so early treatment may reduce its abundance and allow later-germinating natives to establish (Invaders of the Sonoran desert, Undated). ALS inhibitor herbicides are used widely "because of their low use rates, high efficacy, low mammalian toxicity and good selectivity in over 12 major crops" (Brown and Cotterman, 1994 in Heap, 1997). However, at least 33 ALS-inhibitor resistant weed species have been recorded. B. tournefortii was identified to be resistant to Chlorsulfuron in 1992 in Australia (Heap, 1997). In an Australian study by Adkins et al. (1997) the authors determined that B. tournefortii and other winter weeds were still susceptible to chlorsulfuron, despite fears that they may be becomming more resistant with continued use. Yu et al. (2003) reports that, "An African mustard Brassica tournefortii (Gouan.) biotype with a Pro to Ala substitution also was reported as highly resistant to SU and TP [herbicides] but not to IM herbicides (Boutsalis et al. 1999, in Yu et al. 2003)." Biological: Invaders of the Sonoran desert (Undated) state that "It is unlikely that a biological agent, if found, would be approved because many important crop plants are in the genus Brassica (e.g., cabbage, cauliflower, broccoli, brussels sprouts). There are also numerous native mustards that might be threatened by a biological agent". Nutrition The Plants For A Future Database (1997) states that, "Brassica tournefortii prefers light (sandy), medium (loamy) and heavy (clay) soils and requires well-drained soil. It prefers acid, neutral and basic (alkaline) soils. It cannot grow in the shade. It requires moist soil." Reproduction Brassica tournefortii appears to be self-compatible or autogamous, as there is virtually 100 percent fruit set on most plants. A well-developed plant produces between 750 and 9,000 seeds. Seed longevity is unknown, but based on observations of other species of Brassica, it is probably several years. There is little evidence of herbivory or seed parasitism (Sanders and Minnich, 2000). Lifecycle stages North American region: Sanders and Minnich (2000) state that, "B. tournefortii flower or fruit as early as December or January and set seed by February. Most plants are in fruit or dead by April. Time of flowering probably is controlled by the onset of the rainy season. Early flowering may be triggered by hot spells during winter. During warm or dry winters, plants mature at a small size, ripen seeds, and perish by February. Once soils have chilled in fall, rains as small as 4cm cause mass germination. The period of most rapid growth is from the first winter rains or February to April. Within two to three months, plants can grow to a biomass of 3.0 tons/ha-1, but usually less than 0.5 tons/ha-1. Total biomass does not correlate with annual precipitation because hot, dry spells frequently cause plants to reach premature flowering and fruiting in early winter." Reviewed by: Expert review underway Principal sources: Sanders and Minnich, 2000 Brassica tournefortii Compiled by: National Biological Information Infrastructure (NBII) & IUCN/SSC Invasive Species Specialist Group (ISSG) To contribute information, please contact Shyama Pagad. Last Modified: Tuesday, 18 October 2005