Sicyos angulatus (Cucurbitaceae) is a new weed in maize crops in France: Addition to the EPPO Alert List
In France, Sicyos angulatus, a cucurbit of North American origin, was recorded as a weed in 1983 in three maize fields in the Pays Basque (south-west of France). However, its introduction is probably older as it was described in Floras published in the 1970s as a flowering plant which could be used to cover rapidly walls and palisades, or infertile soils. Today, S. angulatus is present in coastal areas from Pyrénées-Atlantiques to Gironde (south-west of France), and along the Rhône valley (south). S. angulatus is mainly found in irrigated maize crops, although a few marginal infestations have been seen in vineyards. Very rapid growth is reported. S. angulatus can cover maize plants entirely and break their stems, thus leading to yield losses (Larché, 2004) . Considering the very rapid development of S. angulatus and the damage it can cause to maize crops, the EPPO Secretariat felt that it could be added to the EPPO Alert List.
Sicyos angulatus (Cucurbitaceae – bur cucumber)
Why: A paper from Larché (2004) attracted our attention to the presence of Sicyos angulatus, a North American cucurbit, in France and other European countries, and to the damage it can cause to crops (maize in particular).
Description: S. angulatus is an annual vine. The plant climbs with long and branched tendrils. Leaves are alternate, hairy, broadly heart-shaped with 5 pointed lobes (22 mm long – 22-30 mm large) and a toothed margin. Monoic species. Small whitish to green flowers (2 mm) with 5 sepals and 5 petals. Small, spiny fruits are produced in clusters (3-20).
Pictures can be viewed on INTERNET:
http://www.comune.ferrara.it/lipu/isola/flora/sicyos.html (infestation in Italy)
Growth can be very rapid, up to 2 m in 3 weeks. Plants can measure up to 7 m long or even more. In Indiana conditions (US), plants established in early spring (May) attained a fresh weight of up to 86 kg and produced almost 80.000 seeds. With later establishment, less biomass and a smaller number of seeds were produced. S. angulatus showed rapid development with periodic germination throughout the growing season.
EPPO region: S. angulatus has been introduced into several European countries as a decorative plant from America. In some places, it has escaped and become a weed. In the literature, there are a few references to its use as a rootstock for cucumbers grown under glass in Europe, but more data is needed on its actual use in practice. S. angulatus is reported from: Croatia (first observed in 1995), Czech Republic, France (South-West), Germany, Hungary, Italy (considered as an invasive weed), Moldova, Norway (thought to have been introduced with imports of soybean seeds), Slovenia, Spain (its presence has been reported, but so far not as an invasive alien), Sweden (first found in 2003), Turkey, United Kingdom.
North America: Canada (Québec, Ontario), Mexico, USA (recorded in 37 states, absent in the west – for more details see USDA plant profile).
Caribbean: Guadeloupe, Martinique.
Asia: China, Japan, Korea Republic.
Habitat: Wet soils, fencerows, shores, swamps, thickets, roadsides and disturbed areas. In France, it was observed that S. angulatus is favoured by floodable loamy clay soils.
Damage: S. angulatus winds around the stems of crops (e.g. maize, soybean) and covers the plants. It is a strong competitor for light and nutrients, which directly leads to yield reduction. In addition, it is a very aggressive climbing plant which pulls maize and soybean plants to the ground creating a harvest loss (fields can be rendered unharvestable). In USA, S. angulatus is listed as a noxious weed in Delaware and Indiana. In Japan, it is considered as a major introduced weed species. It occurs in cultivated and uncultivated fields and it is also invading native vegetation. Observations made in Japanese maize fields showed that yield was decreased by 80% by a population of 15-20 plants/10 m² and by 90-98% with 28-50 plants/10 m².
Dispersal: Plant dissemination is mainly ensured by dispersal of seeds. These seeds, which are produced in large numbers, are readily scattered by mechanical harvesters and animals. Fruits with prickly hairs may also help dissemination. Over long distances, trade of seeds contaminated with S. angulatus seeds can ensure plant spread.
Pathway: Seeds of crops (e.g. maize, soybean) contaminated with S. angulatus seeds, soil or machinery with viable S. angulatus seeds.
Possible risks: S. angulatus is reported as a weed in arable crops such as maize and soybean which are major crops in the EPPO region. Significant losses are occasionally reported. In addition, it is also observed in non-cultivated areas competing with native species. Herbicides can be used against S. angulatus but this is difficult in cases of heavy infestations or near water courses. Cultural control (tillage, crop rotation) can help to reduce weed populations. Although, S. angulatus is reported from several EPPO countries, more data is needed on its impact on crops and native vegetation in the areas where it occurs.
EPPO RS 2004/092
Panel review date - Entry date 2004-06
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Larché, J.F.; (2004) Sicyos angulatus, nouvelle adventice du maïs dans le Sud-Ouest de la France. Phytoma – La Défense des Végétaux, no. 571, 19-22.
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