Solanum elaeagnifolium


European and Mediterranean Plant Protection Organization Organisation Européenne et Méditerranéenne pour la Protection des Plantes

Identity

Scientific name: Solanum elaeagnifolium Cavanilles

Synonyms: Solanum dealbatum Lindley, Solanum flavidum Torrey, Solanum hindsianum Bentham, Solanum leprosum Ortega, Solanum roemerianum Scheele, Solanum saponaceum Hooker fil in Curtis, Solanum texense Engelman & A. Gray, Solanum uniflorum Meyer ex Nees

Taxonomic position: Solanaceae

Common names: Silver-leaf nightshade, white horse-nettle, tomato weed, silverleaf nettle, bitterleaf nightshade, bitter apple, silverleaf bitter apple, bull nettle, prairie berry (English); morelle jaune (French); ölweidenblättriger, nachtschatten (German); meloncillo del campo, quillo-quillo, revienta caballo, tomatillo, trompillo (Spanish); Tähtikoiso (Finnish); gfck/b kbytqyjkbcnysq (Russian); bitterappel, bloubos, satansbos, silwerblaarbitterappel (Afrikaans); chouka assafra, chouika, chouk jmel, hassika matechat jmel, zririga (in Morocco)

Notes on taxonomy and nomenclature: The name Solanum elaeagnifolium is universally accepted, though the species displays considerable morphological variation, especially in the Americas, confusing its taxonomic status. Morton (1976) proposed that the Argentine form was a separate subspecies, but Symon (1981) concluded that this form also occurs in North America and is thus a natural variant of the same species. Several varieties and forms have been described, though clonal reproduction permits the coexistence of different variants, suggesting that classification at the varietal level should be avoided unless genetic differences are confirmed (Stoltsz, 1994; Heap & Carter, 1999)

EPPO code: SOLEL

Phytosanitary categorization: EPPO A2 List no. 342

Geographical distribution

EPPO region: Algeria, Croatia, Cyprus, Egypt, France, Greece, Israel, Italy, Republic of Macedonia, Morocco, Serbia and Montenegro, Spain, Syria, Tunisia

Asia: India (Karnataka, Tamil Nadu), Israel, Taiwan

Africa: Algeria, Egypt, Lesotho, Morocco, South Africa, Tunisia, Zimbabwe

North America: Mexico, USA (Alabama, Arizona, Arkansas, California, Colorado, Florida, Georgia, Hawaii, Idaho, Illinois, Indiana, Kansas, Kentucky, Louisiana, Maryland, Mississippi, Missouri, Nebraska, Nevada, New Mexico, North Carolina, Ohio, Oklahoma, Oregon, South Carolina, Tennessee, Texas, Utah, Washington)

Central America and Caribbean: Guatemala, Honduras, Puerto Rico

South America: Argentina, Chile, Paraguay, Uruguay

Oceania: Australia (all states).

History of introduction and spread

S. elaeagnifolium is native to north-east Mexico and south-west USA where it is a weed (Robinson et al., 1978). It is also considered native to Argentina, the nature of the insect herbivorous fauna suggesting that this distribution is secondary. It has been introduced to other parts of North America including California and Florida and is now widespread in all but the Great Lakes and New England regions (USDA-NRCS, 2005). Invasions of the weed have also occurred in Australia, southern India, South America, southern Africa and around the Mediterranean Basin. Further spread is very likely. It was newly recorded in southern Taiwan and the Penghu Islands in 2002 (Hsu & Tseng, 2003). It is reported but unconfirmed in Turkey.

Introduction to Morocco is believed to have resulted from the import of contaminated crop seeds in 1958 (Tanji et al., 1984), and it now infests 50 000 ha in the Tadla region and it is spreading to other regions such as El-Kelâa des Sraghna and Marrakech. In South Africa, it is thought to have been imported as a contaminant of pig fodder around 1905 (Wassermann et al., 1988), and/or hay during the 1940s or 1950s, being recorded as a problem in 1952 and declared a weed in 1966. Similarly, infestations in South Australia are linked to imports of contaminated hay from North America during the 1914 drought, although the weed was first recorded in New South Wales in 1901 and then in Victoria in 1909 (Heap et al., 1997). Later infestations in Western Australia appeared from contaminated Sudan grass (Sorghum sudanense) introduced from eastern Australia (Heap & Carter, 1999). In the USA, where the plant is native to some south-western States, contaminated ballast and bedding used in railway cattle wagons led to the introduction of the weed into California in 1890 (Goeden, 1971).

Morphology

Plant type

S. elaeagnifolium is a seed- or vegetatively-propagated (therophyte, chamaephyte, hemicryptophyte or geophyte), broadleaved herbaceous and woody perennial.

Description

S. elaeagnifolium is multistemmed, up to 1 m tall, the aerial growth normally dying back during winter, with an extensive root system spreading to over 2 m deep (Fig. 1). The term ‘rhizome’ cannot be used in the case of this plant as fragments on any part of the roots can regenerate.

Figure 1.

Extensive root system of S. elaeagnifolium. Berre l’Etang, Bouches-du-Rhône, France, April 2005. Photo: Christelle Chevrat.

Stems are cylindrical, sparingly branched, with a few scattered reddish prickles, herbaceous except at the base.

Leaves are dark green to pale greyish green, petiolate, lanceolate, obtuse or acute at the tip, rounded or truncate at the base, with entire or wavy margin, 2.5–10 (max 16) cm long and 1–2.5 (max 4) cm wide, petiole 0.5–2 cm long, sometimes slightly lobed or with undulate margins (Figs 2 & 3). Leaves, stems and calyx are densely pubescent, giving the plant its typical silver-green appearance. Foliage is covered with star-shaped hairs. Yellow- to brown-coloured prickles usually occur on the stems and also the main veins of the leaves.

Figure 2.

S. elaeagnifolium seedling. Surroundings of Kairouan, Tunisia, May 2006. Photo: Sarah Brunel.

Figure 3.

S. elaeagnifolium invading a potato field. Surroundings of Kairouan, Tunisia, May 2006. Photo: Sarah Brunel.

The inflorescence is a solitary cyme of 1–7 flowers, with long peduncules (5–20 mm). The calyx measures 5–7 mm, with 2–4 linear lobes. The corolla is 25–35 mm large and is orbicular, generally bright blue to purple but sometimes white with yellow anthers of 7–9 mm (Fig. 4).

Figure 4.

S. elaeagnifolium inflorescence in a wheat field. Surroundings of Kairouan, Tunisia, May 2006. Photo: Sarah Brunel.

The fruit is an irregularly dehiscent berry, initially spherical, green (with white patches) and fleshy, drying and becoming yellow to orange (10–15 mm in diameter) at maturity (Fig. 5). A single plant generally produces 40–60 fruits, each containing 60–120 seeds, smooth, flat, greenish-brown, 2–3 mm in diameter, closely resembling those of tomatoes.

Figure 5.

Fruit of S. elaeagnifolium. Surroundings of Kairouan, Tunisia, May 2006. Photo: Sarah Brunel.

Invasions of croplands and pastures by S. elaeagnifolium are most conspicuous during midsummer when the plants are flowering (Fig. 6). In such infestations, the plants are easily identified by the abundance of blue or purple flowers and the orange-yellow mature berries that appear later in the season.

Figure 6.

S. elaeagnifolium invading an olive orchard. Surroundings of Kairouan, Tunisia, May 2006. Photo: Sarah Brunel.

Similarity to other species

In the EPPO region, S. elaeagnifolium is very distinct from other native or introduced Solanum spp. Elsewhere in the world, it has been confused with S. coactiliferum, S. esuriale and S. karsensis in Australia (Heap et al., 1997; Heap & Carter, 1999), S. carolinense in Texas, USA (Gorrell et al., 1981), and S. panduriforme in South Africa where hybrids have also been identified (Wassermann et al., 1988). However, variation within introduced populations is considered to be the result of multiple introductions rather than hybridization with native Solanum species (Stoltsz, 1994; Heap et al., 1997). (See Notes on taxonomy and nomenclature, above.)

Biology and ecology

General

S. elaeagnifolium is a perennial geophyte with roots, summer-growing, dying back in late autumn, and surviving off its rootstocks during the winter.

It has four different growth forms: from seeds (as a therophyte) germinating from spring through summer; from buds above soil level giving new shoots in spring (chamaephyte); from buds at the soil surface (hemicryptophyte); from buds buried in the soil, which regenerate from its roots (horizontal or vertical), from which new shoots arise (geophyte).

It mainly reproduces vegetatively, from buds on underground fragments. Fragments as small as 0.5 cm long and as deep as 20 cm deep can regenerate. Sections of taproot may maintain their viability for up to 15 months (Molnar & McKenzie, 1976). Ten-day-old seedlings are able to regenerate. Sprouting is enhanced by the removal of the aerial parts of the parent plants or by cultivation. This aggressive vegetative growth from deep rootstocks makes S. elaeagnifolium very difficult to control, both mechanically and chemically.

Reproduction by seed is secondary, though seeds are highly viable and last at least 10 years in soil. High levels of dormancy and infrequent germination can lead to the establishment of extensive viable seed banks.

Studies indicate that 10% of seed is still viable after passing through the digestive tract of sheep (Washington State Noxious Weed Control Board, 2006). Seeds require fluctuating temperatures to germinate. Boyd & Murray (1982) obtained a maximum germination rate of 57% when they germinated seeds at 20°C for 16 h and at 30°C for 8 h; light and darkness had no effect. They also found that a pH of 6 or 7 was optimal for germination. Other work indicates that immersing seeds in running water for relatively long periods may improve germination rates (Rutherford, 1978). Factors controlling seed germination are poorly understood, however, the reproductive biology of S. elaeagnifolium is comprehensively reviewed by Heap & Carter (1999), Parsons (1981) and Richardson & McKenzie (1981).

The life cycle of the plant is composed of 5 phases: vegetative regeneration and germination during spring; vegetative development, the duration of which depends on the biotope; flowering from spring to the end of summer and fructification from the end of spring until autumn.

Pollination is believed to occur via insects. Individual plants produce up to 200 berries per growing season, approximating to 1500–7200 seeds per plant. Factors influencing seed ecology, viability and germination are comprehensively reviewed by Heap & Carter (1999), who report the chromosome number of S. elaeagnifolium as 2n = 24.

Habitat

S. elaeagnifolium is mainly a weed of cultivated land, orchards, managed grasslands and associated man-made habitats such as natural grasslands, riverbanks/canalsides, rail/roadsides and wastelands (Fig. 7). It appears to be adapted to a wide range of habitats and soil conditions, but appears mostly in areas of relatively low annual rainfall (250–600 mm) (Parsons, 1981; Heap & Carter, 1999). In Australia and South Africa, the largest infestations occur in cropping and grazing land, with smaller infestations found in irrigated pastures, orchards and vineyards, roadsides, channel banks and stockyards (Wassermann et al., 1988; Heap & Carter, 1999). In particular, the weed thrives on disturbed land and although undisturbed pastures and natural vegetation are not normally invaded, this is facilitated by trampling caused by livestock.

Figure 7.

An infestation of S. elaeagnifolium on a roadside, probably introduced with the growing media of the ornamental plant. Surroundings of Kairouan, Tunisia, May 2006. Photo: Sarah Brunel.

Environmental requirements

  • S. elaeagnifolium tolerates Mediterranean, steppe and mild climates with relatively high summer temperatures and low annual rainfall (Parsons, 1981; Heap et al., 1997). It has been suggested that cool summers and high annual rainfall are factors that could prevent invasion in certain areas (Heap & Carter, 1999) and this is consistent with the distribution of the weed in Australia and South Africa. However, in Europe, its northern potential limit may be more dependent on winter temperatures. Established plants are sensitive to frost and waterlogging but are tolerant to saline conditions and highly resistant to drought (Wassermann et al., 1988). Full sunlight is most favourable for growth, and shading reduces plant vigour. It requires high temperatures (20–34°C) for normal germination and growth. Germination is advanced under favourable moisture conditions, notably heavy rains, and by alternating temperatures. Once established, the plants are highly resistant to drought and are widespread in semiarid areas, but will also thrive under irrigated conditions in these areas. Although summer-growing, the weed is very adaptable climatically and, in Australia, also occurs in winter rainfall areas (Cuthbertson et al., 1976). It is recorded at up to 1200 m altitude (Californian Department for Food and Agriculture, 2006).

S. elaeagnifolium can adapt to different soil types. For example, in Australia, the heaviest infestations were observed on sandy soils with low organic matter (Heap & Carter, 1999).

Climatic and vegetational categorization

S. elaeagnifolium is found in areas with a hot dry summer and a cool wet winter. In its native range, it seems hardy only to zone 9 (–7 to –1°C) but as a weed it is hardy to zone 6 (–23 to –18°C) as, for example, in the USA. It is associated with the following vegetation zones: Mediterranean sclerophyllous forests and temperate steppes.

Uses and benefits

Despite its confirmed adverse toxicity to livestock (e.g. Dollahite & Allen, 1960; Molnar & McKenzie, 1976), South African cattle and wild antelope browse S. elaeagnifolium during spring and early summer with no ill effects (Wassermann et al., 1988), and the plant has also been pelleted and successfully fed to livestock. The steroidal alkaloid Solasodine used in the preparation of contraceptive and corticosteroid drugs has been commercially extracted from S. elaeagnifolium berries in India (Maiti, 1967) and Argentina, making it the most promising source among Solanum species investigated (Heap et al., 1997). Recent studies have identified other potential uses for S. elaeagnifolium as plant extracts have shown moluscicidal and nematicidal activity, as well as cancer-inhibiting activity.

Pathways of movements

Natural dispersal

Spread can occur both vegetatively from cut root sections, and via seeds. The fruit can float, and can be dispersed over long distances along rivers and streams, especially during floods. Seeds are also easily and widely dispersed by agricultural machinery and tools, vehicles, in bales of hay and alfalfa, and in the dung of livestock and wild animals. Although the plants die back in winter, ripe fruit are retained on dead branches and may be dispersed by wind. Dried plants may also blow like tumbleweeds, spreading seed along the way (Boyd et al., 1982). S. elaeagnifolium has a particular pattern of spreading. From the first point of introduction and establishment, the plant spreads in all directions. This spreading is not continuous but occurs in leaps. The space between the neighbouring colonies increases with distance from the centre (Yannitsaros et al., 1974).

Agricultural practices

Spread is possible by livestock and manure, irrigation water, agricultural machinery, rooted nursery plants, contaminated straw or seeds. Vehicles and tools used in agriculture, bulldozers and other earth-moving equipment can also spread the weed by transporting both seeds and sections of root. Soil, sand and ornamental plants can be contaminated by fragments of roots or seeds of S. elaeagnifolium (Taleb et al., 2007).

Movement in trade

S. elaeagnifolium has no ornamental value and has only occasionally been introduced for its aesthetic characteristics (Chalghaf et al., 2007), thus introductions worldwide appear to have been unintentional. Movements of contaminated fodder are proposed as the mode of introduction into South Africa and Australia, where it is suspected that multiple, rather than single, introductions have occurred. Crop seed, notably grain and fodder crops that are contaminated by the weed, are another major source of infestation (e.g. in Australia, Morocco, South Africa and California). The main crops reported to have contained S. elaeagnifolium are maize (Zea mays) and lucerne (Medicago sativa).

Impact

S. elaeagnifolium has a negative impact mainly on crop production but also on livestock production, on the environment and on trade and international relations.

Effects on plants

By being a spring species, the life cycle of S. elaeagnifolium perfectly coincides with those of spring crops. In autumnal crops, the invasive plant is only present during the second half of their life cycle.

S. elaeagnifolium competes for moisture and nutrients with many crops. The most affected crops are Gossypium hirsutum (Cotton), Medicago sativa (lucerne), Sorghum bicolor (common sorghum), Triticum aestivum (wheat), Zea mays (maize) and to a lesser extent Arachis hypogaea (groundnut), Asparagus officinalis (asparagus), Beta vulgaris var. saccharifera (sugar beet), Citrus spp. (citrus), Cucumis sativus (cucumber), Lycopersicon esculentum (tomato), Olea europaea subsp. europaea (olive), Prunus persica (peach), Solanum tuberosum (potato), Sorghum sudanense (Sudan grass) and Vitis vinifera (grapevine). Infestations are more serious in drylands, although irrigated croplands are also very prone to invasion, and many other horticultural and orchard crops are affected.

In Morocco, losses of up to 64% in maize without treatment (Baye & Bouhache, 2007) and 78% in cotton have been reported. In Australia, wheat losses varied from 12 to 50% (Cuthbertson, 1976) according to climatic conditions and weed density, but were highest at dry, sandy sites or during low rainfall years (Heap & Carter, 1999). In the USA, sorghum and cotton yield losses under optimal moisture regimes were 4–10% and 5–14%, respectively (Robinson et al., 1978), with 75% losses in cotton grown under semiarid conditions.

S. elaeagnifolium also displays allelopathic effects, especially in cotton fields (Californian Department for Food and Agriculture, 2006; Bothma, 2002). Both perennial and annual pastures are adversely affected, with pasture establishment delayed and pasture production reduced.

As a perennial weed, S. elaeagnifolium is very difficult to control, and often disrupts tillage and harvesting practices. It can block drains and irrigation channels. Severe infestations could even limit the types of crop that could be successfully cultivated in the USA (Davis et al., 1945). The presence of S. elaeagnifolium can lead to less effective land usage, reduced monetary returns, and increased production costs arising from control operations.

In California, S. elaeagnifolium has been reported as a reservoir for Lettuce chlorosis virus (McLain et al., 1998) which is transmitted by Bemisia tabaci. It is also recorded as a secondary host of several insect pests, the most important being Leptinotarsa decemlineata (Hare, 1990), Anthonomus eugenii (Patrock & Schuster, 1992), Globodera rostochiensis and Globodera pallida. In Tunisia, the plant has been reported as a potential source of Potato virus Y (PVY) propagation (Boukhris-Bouhachem, 2007).

The berries of S. elaeagnifolium are toxic to livestock, particularly when mature (Burrows et al., 1981). Symptoms include excessive salivation, nasal discharge, respiratory complications, bloating, trembling and diarrhoea (Parsons, 1981). The plant affects horses and causes mortality to sheep (Molnar & McKenzie, 1976) while goats are apparently unaffected (Parsons, 1981; Wassermann et al., 1988).

Environmental and social impact

Although S. elaeagnifolium is primarily associated with cultivated land, it may also invade adjoining areas (e.g. roadsides, river- and canal-sides). It may replace natural vegetation in areas of overgrazed rangeland and in heavily trampled areas around waterholes. However, the environmental impacts are limited in comparison to the impacts on cultivated lands.

Agricultural land infested with S. elaeagnifolium loses considerable rental and resale value. In Morocco, the value of infested fields decreased by 25% (Gmira et al., 1998). In the USA, farms have been abandoned because of infestation (Parsons, 1981).

Summary of invasiveness

S. elaeagnifolium has been introduced from North America to Africa, Asia, Australia, Europe and South America where it is an important weed of croplands and pastures, mostly in cultivated land, disturbed areas and overgrazed areas with low rainfall. The invasiveness is aggravated by high seed production and an extensive root system that promotes vegetative multiplication and renders conventional control methods very difficult. Other negative effects include hindering commercial cropping activities, harbouring agricultural pests, being toxic to livestock and reducing land values. The plant is officially declared as a noxious weed in several countries.

Control

Cultural control

S. elaeagnifolium is very difficult to control and it is essential to keep it out of uncontaminated areas. Any isolated plants and small patches should be treated as soon as they appear (Parsons, 1981). In endangered areas, regular inspections during midsummer when plants are flowering and vigilance during harvesting are recommended (Heap et al., 1997). Grain and fodder crops harvested in contaminated areas should be inspected for contamination. It is also recommended to check hay for S. elaeagnifolium berries before feeding it to cattle. This will prevent livestock poisoning and the introduction of seeds into uninfested areas (Californian Department for Food and Agriculture, 2006). In Australia, movements of livestock, mainly sheep, account for most new infestations and stock from infested areas should be quarantined for 14 days to allow all seed to pass through the digestive tract and thus prevent further spread (Heap et al., 1997). Unauthorized vehicles should also be kept out of infested properties, and vehicles and machinery should be thoroughly checked for berries and root fragments and cleaned on leaving infested areas. The development of S. elaeagnifolium is reduced in irrigated crops and where dense crop stands can be maintained (e.g. with lucerne). It is also controlled by intensive cropping in wheat-sorghum-wheat rotations and by sowing Eragrostis curvula in pastures. Viljoen & Wassermann (2004) studied the suppression of S. elaeagnifolium by three pasture species under dryland conditions in a field trial. They showed that Medicago sativa and particularly Digitaria eriantha have the potential to suppress S. elaeagnifolium provided that dense stands be achieved and maintained. Although intensive browsing by cattle is reported to reduce fruit set (Wassermann et al., 1988), the removal of all cattle from infested pasture is recommended as selective grazing increases the dominance of the unpalatable S. elaeagnifolium.

The use of seed free from S. elaeagnifolium and deep ploughing at the beginning of summer are recommended as preventative measures.

Mechanical control

In winter crops, regular tillage during the preceding summer weakens S. elaeagnifolium because of its lack of growth in winter. In summer crops (e.g. cotton, sorghum), dense crops may suppress the weed and regular tillage or clearing prevent fruit set (Davis et al., 1945). Small infestations may be hand-pulled, but this should be repeated several times during the growing season. The plant has sharp spines and gloves should be worn for hand-pulling.

Eradication action has been undertaken in the south of France (Agence Méditerranéenne de l’Environnement, 2006). The entire root system of the plant was taken out, and contaminated ground in the surroundings of the plant buried in a hole three metres deep. In cases of mechanical control, all parts of the plant, including the roots, have to be collected and destroyed. Considering the viability of seeds, monitoring of the treated area should last for at least 10 years.

Control methods in Morocco are reviewed by Ameur et al., 2007.

Chemical control

Experience in South Africa (Wassermann et al., 1988) and Australia (Parsons, 1981; Heap et al., 1997) has shown that S. elaeagnifolium is generally very difficult to control with herbicides, including soil sterilants and nonselective chemicals. None were considered effective and affordable for large infestations. Spot-spraying treatments with picloram proved effective in Australia and Greece, whereas glyphosate was unreliable and others less effective (Eleftherohorinos et al., 1993; Heap et al., 1997). Herbicides were considered to be more effective when applied during optimal moisture conditions and during the ‘green berry’ stage of the weed (Stubblefield & Sosebee, 1986).

Many experiments have been conducted in Morocco. Zaki et al. (1995) showed a significant density and biomass reduction of S. elaeagnifolium with the application of glyphosate added with ammonium sulphate at the flowering and fructification stages, followed by mowing 2, 3 or 4 weeks after treatment. The combination of glyphosate and mechanical control allowed a reduction of density (> 92%), biomass (> 94%) and fruit production (100%) of S. elaeagnifolium.

Baye et al. (2007) found that systemic herbicides such as glyphosate, sulfosate and amitrole have shown to be very effective and are principally recommended for nonselective treatments in orchards (olive, citrus, fruit trees) and fields at postharvest (cereals, sugar beet, market gardening). These require special application conditions and are recommended above all in cases of severe infestation. Phenoxy herbicides, imazapyr and bromacil are used for weed control on roadsides, whether forested or nonforested and possibly on unused plots. Bromacil can be used in citrus orchards that are at least four years old, but only in heavily infested areas in view of its high cost.

Biological control

S. elaeagnifolium supports a diverse insect herbivorous fauna in its area of origin (Goeden, 1971), some of which have been tried as biological control agents notably in South Africa (Olckers & Zimmermann, 1991) and Australia (Wapshere, 1988). Two leaf-feeding beetles, Leptinotarsa texana and Leptinotarsa defecta, are established in South Africa following release in 1992, though only L. texana causes considerable damage, by reducing growth and fruit production (Hoffmann et al., 1998; Olckers et al., 1999). Morocco has more recently expressed an interest in importing these biological control agents (Klein, 2001). Sforza and Jones (2007) state that biological and impact studies of Leptinotarsa spp. in Europe should be conducted. The native leaf-galling nematode Ditylenchus phyllobius has been used with some success in the USA (Northam & Orr, 1982). It has become established in India, probably after having been introduced with the plant. It was considered as a biological control agent in South Africa, but was not released due to doubts about its host specificity (Olckers & Zimmermann, 1991). A foliar nematode, Orrina phyllobia, which causes leaf and stem galling has also been studied (Roche, 1991). Nevertheless, biological control can only be considered as one component of an integrated management plan, to be used in conjunction with specific management practices.

Regulatory status

S. elaeagnifolium has accidentally been introduced into several countries via contaminated fodder crops. Consignments of seeds, containers and packing material, plants for planting with soil, soil as a consignment, soil as a contaminant, and livestock also present a high phytosanitary risk for the countries that import these products from infested countries. S. elaeagnifolium is declared invasive in several countries, including Morocco where it is considered as the country's most noxious weed (Taleb, 2006) and is under official control. In Belarus, Russia and Ukraine where it is a quarantine pest, grain consignments are required to be free from its seeds. This plant is also included in lists of plants controlled under noxious weed legislation in Australia, South Africa and approximately 20 states of the USA (USDA-NRCS, 2005). Moreover, the sale of contaminated agricultural products with Solanum elaeagnifolium is prohibited in South Africa (Wassermann et al., 1988).

In 2006, S. elaeagnifolium was recommended for regulation in the EPPO region as an A2 pest.

Phytosanitary measures could include that plants for planting with growing medium attached originating from countries where the pest is present should be grown in a growing medium free from the pest or should come from a pest-free area or pest-free place of production for S. elaeagnifolium.

Soil/growing medium (with organic matter) as a commodity originating from countries where the pest is present should be collected in a pest-free place of production or pest-free area for S. elaeagnifolium.

Seeds of Gossypium spp., Hordeum indicum, Medicago sativa, Nicotiana tabacum, Sesamum indicum, Sorghum bicolor, Triticum spp., or Zea mays from countries where the pest occurs should be cleaned or should come from a pest-free area or pest-free place of production for S. elaeagnifolium.

Consignments of grain (Hordeum spp., Sesamum indicum, Sorghum bicolor, Triticum spp, Zea mays) from countries where the pest occurs should be cleaned, or should come from a pest-free area or pest-free place of production for S. elaeagnifolium.

Cleaning or disinfection of imported machinery or vehicles from countries where the pest occurs is recommended. Publicity to enhance public awareness on pest risks is a recommended measure as S. elaeagnifolium can be a contaminant on footwear. Use of clean containers and packaging material is also recommended.

Appendix

References for geographical distribution

Ancillary