Vincetoxicum rossicum (European swallow-wort)

Pictures

Picture	Title	Caption	Copyright
Title Stem and flowers Caption Stem and flowers of V. rossicum. Copyright Frances Lawlor	Stem and flowers	Stem and flowers of V. rossicum.	Frances Lawlor
Title Habit Caption Habit of V. rossicum. Copyright Frances Lawlor	Habit	Habit of V. rossicum.	Frances Lawlor
Title Flowers Caption Flowers of V. rossicum. Copyright Frances Lawlor	Flowers	Flowers of V. rossicum.	Frances Lawlor
Title Fruits Caption Fruits of V. rossicum. Copyright Frances Lawlor	Fruits	Fruits of V. rossicum.	Frances Lawlor

Identity

Preferred Scientific Name

• Vincetoxicum rossicum (Kleopow) Barbar.

Preferred Common Name

• European swallow-wort

Other Scientific Names

• Alexitoxicon rossicum (Kleopov) Pobed.
• Antitoxicum rossicum (Kleo.) Pobed
• Cynanchum rossicum Kleopow
• Cynanchum rossicum Borhidi
• Vincetoxicum officinale var. rossicum (Kleopow) Grodz.

International Common Names

• English: dog-strangling vine; pale swallow-wort

Local Common Names

• Canada: dompte-venin de Russie
• USA: swallowwort; swallow-wort

Summary of Invasiveness

V. rossicum is a herbaceous perennial climbing vine native to Ukraine and southwestern European Russia. It was introduced into North America for ornamental purposes and has spread extensively throughout the lower Great Lakes Basin, particularly Lake Ontario, including New York State, USA and Ontario, Canada. Self-fertility and large numbers of wind-borne seeds ensure rapid dispersal of V. rossicum to new sites. Small patches of V. rossicum can coalesce to form very large, monospecific stands which can outcompete native vegetation resulting in a change in habitats and a decrease in biodiversity. V. rossicum is allelopathic and can alter the microbial composition in the rhizosphere preventing the growth of sensitive plant species. In the USA, competition from V. rossicum is putting pressure on the rare and endangered species Asplenium scolopendrium var. americanum. In addition to this, V. rossicum has been shown to decrease insect biodiversity and may have negative impact on the reproduction of the Monarch butterfly, Danaus plexippus.

Taxonomic Tree

• Domain: Eukaryota
•     Kingdom: Plantae
•         Phylum: Spermatophyta
•             Subphylum: Angiospermae
•                 Class: Dicotyledonae
•                     Order: Gentianales
•                         Family: Asclepiadaceae
•                             Genus: Vincetoxicum
•                                 Species: Vincetoxicum rossicum

Notes on Taxonomy and Nomenclature

Other names for the genus Vincetoxicum Wolf (1776) include Vincetoxicum Medik., Alexitoxicum St. Lag., Cynanchum (L.) Pers., Cynanchum (L.) R. Br. and Antitoxicum Pobed. No consensus exists for the distinction between Vincetoxicum and Cynanchum. Liede and Täuber (2002) found significant distinctions between Old and New World Cynanchum species, more so than between other established genera of Asclepiadaceae. Liede (1996) separated Vincetoxicum from Cynanchum on the basis of the presence of certain alkaloids and glycosides in Vincetoxicum that are lacking in Cynanchum, using these as indicators of phylogenetic distance. Others find the variation of these genera to be too continuous to separate them (Woodson, 1941; Kartesz, 1999).

Description

V. rossicum is a perennial herbaceous suberect, climbing and twining vine growing from a fibrous root system with several subterranean buds at the stem base producing one (or more) stems which annually grow to 1-3+ m high. Leaves are opposite, 9-12 cm long, oblong to ovate, acuminate, rounded to subcordate at base, with short (5-10 mm) petioles.

Flowers are in groups of 4-6 in umbelliform cymes in the axils of leaves, peduncles 2-5 cm long, pedicels pubescent. Creamy pale to dark maroon corolla, 4-6 mm diameter, corolla lobes fleshy, glabrous, deltoid, 1.5-3 mm, segments joined by a connective membrane 1/2 their length. The fruits are slender, smooth follicles, 4-6 cm long by 0.5 cm wide, often in pairs. Seeds comose.

Plant Type

Distribution

V. rossicum is native to Ukraine and southwestern European Russia. V. rossicum has been introduced into North America where infestations are concentrated in the Lower Great Lakes basin, especially the Lake Plain of New York State, USA and southern Ontario, Canada. Additional reports come from Missouri (USDA-NRCS, 2016). The presence of V. rossicum has also been reported in British Columbia and Quebec, Canada, (USDA-NRCS, 2016). Populations of V. rossicum have been identified in Norway, where invasive tendencies were noted (Lauvanger and Borgen, 1998).

Distribution Table

The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

History of Introduction and Spread

The first record of V. rossicum in North American was collected in 1885 from cultivation in Victoria, British Columbia, Canada (Moore, 1959; Sheeley and Raynal, 1996). The first record in eastern North America was in 1889 at Toronto Junction, Ontario, Canada (Moore, 1959). The earliest state record in the USA was 1897 in Monroe and Nassau Counties, New York (Sheeley and Raynal, 1996).

Risk of Introduction

The accidental introduction of V. rossicum will continue via agricultural commodities, contaminated soil and vines/seeds caught on equipment. V. rossicum and the closely related V. nigrum are included on invasive plant lists for New York State and the New England states, but the lists have no regulatory power. In addition to this the attractive flowers and pods invite collection and introduction of V. rossicum into new areas by the public.

Habitat

V. rossicum is found in shrub steppe, meadow steppe and steppe meadow (Visulina, 1957), on stony soil high in calcium and carbonate, in its native regions north of the Black Sea in the Ukraine and southwestern European Russia.

In North America V. rossicum is present in a range of habitats from dry and sunny successional fields and limestone barrens to alluvial woodlands, all on lime-based soils. It is very competitive in open areas, particularly associated with disturbances, such as shallow soils susceptible to stresses such as freeze-thaw cycles and flooding.

V. rossicum is also associated with disturbed and waste areas such as quarries and transportation corridors. Once established, V. rossicum readily moves into natural and semi-natural habitats and is a weed of woodlands.

Habitat List

Biology and Ecology

Genetics
Moore (1959) reports the chromosome number for V. rossicum (Cynanchum medium R. Br.) as 2n=22.

Physiology and Phenology

Polyembryonic seeds germinate in autumn and spring, with improved germination after vernalisation, yielding 1-4 seedlings. The fibrous root system radiates from the crown. Seedlings have pointed ovate leaves. V. rossicum becomes reproductive during the second year, or later. Fruit dehisce and release coma (tufts of hairs)-bearing wind-borne seeds from mid-August until early October in New York State, USA. Plants senesce after seed dispersal. Dead stems persist through winter and the successive growing season. Perennating buds on the root crown readily sprout after top destruction. Plants emerge in May and expand rapidly. Twining begins as flower buds begin to enlarge. Flowering begins in mid to late May, and ends by mid-July.

Reproductive Biology

Reproduction of V. rossicum is amphimictic, by entomophily or self-pollination. Flowers are visited mainly by Hymenoptera, Diptera and Coleoptera (Christensen, 1998; Lawlor, 2000). Seed longevity is unknown. Productivity in fully irradiated monospecific stands was over 2000 seeds/m² (Sheeley, 1992). Seed production is greatly reduced under low light conditions. Polyembryony yields 1-4 seedlings per seed (Sheeley, 1992; Cappuccino et al., 2002). Seed weight and seedling mass are related to polyembryony, which increased establishment success on bare soils, but not in competition with grasses (Cappuccino et al., 2002).

Associations

The Monarch butterfly, Danaus plexippus, will lay eggs on V. rossicum, but larvae die (Casagrande and Dacy, 2001). This genus may therefore adversely affect Monarch butterflies by disrupting the obligate relationship of Monarch reproduction on Asclepias species.
V. rossicum appears to be able to manipulate native arbuscular mycorrhizal fungi to the detriment of native plant species (A DiTomasso, Cornell University, Ithaca, NY, USA, personal communication, 2003).

Environmental Requirements

V. rossicum tolerates more precipitation in North America than in eastern Europe; mean precipitation 957 mm in Watertown, New York, USA, versus 519 mm in Kharkov, Ukraine, for example. Habitats include meadows, successional shrublands, hedgerows, copses and woodland from rocky shores to more than 400 m. V. rossicum has a preference for lime-derived soils. V. rossicum is present in areas with a mean winter temperature of -11-0.7°C and summer temperatures of 20.7-26.4°C with an annual precipitation of 776-1206 mm per year (ISSG, 2016).

Latitude/Altitude

Air Temperature

Rainfall

Rain Regime

Soil Tolerances

Soil drainage

• free
• seasonally waterlogged

Soil reaction

• acid
• alkaline
• neutral

Soil texture

• light
• medium

Special soil tolerances

• shallow

Natural Enemies

Notes on Natural Enemies

Eight insect species have been noted on Vinctoxicum spp. in Europe and are being considered as potential biocontrol agents (Tewksbury et al., 2002). No record of phytophagous insects on V. rossicum has been found in North America, although Cappuccino has observed transfer of the milkweed bug, Oncopeltus fasciatus, onto V. rossicum (N Cappuccino, Carleton University, Ottawa, Ontario, Canada, personal communication, 2003). In Europe, Vincetoxicum species are important alternate hosts for cronartium rust and resin-top, Cronartium flaccidum, in conifer trees, although no information is available on the susceptibility of V. rossicum to the rust (Kaitera, 1999).

Means of Movement and Dispersal

Natural Dispersal

Seeds of V. rossicum are wind-dispersed, bearing the tuft of hairs, or coma, typical of the milkweed family. A study by Cappuccino et al. (2002) found that seeds travelled up to 18 m at an average wind speed of 11.2 km/h from their release point, with 50% falling within 2.5 m.

Accidental Introduction

V. rossicum may be accidentally transported by man, through garden cultivation and possible decorative use of dried fruits on the vine, as witnessed in an infested area in Monroe County, New York, USA, after wreaths of the vine were sold in a craft shop. Seeds have been observed in the trouser cuffs of hikers and hunters and can be moved with hay sales from infested hay fields, sale of nursery stock and Christmas trees.

Intentional Introduction

V. rossicum was intentionally introduced into North America for ornamental and horticultural purposes.

Pathway Vectors

Plant Trade

Impact Summary

Economic Impact

In the USA, V. rossicum has been reported as a major problem in corn and soybean fields where it decreases yields. It is also a problem for Christmas tree producers (ISSG, 2016).

Environmental Impact

Impact on Habitats

V. rossicum can successfully dominate susceptible natural areas where it can form dense stands which can outcompete and smother native plant species. As a result, this leads to a change in habitat structure which can lead to loss of biodiversity in both flora and fauna. Change in habitat structure in grassland bird habitats is of concern for diminishing populations of migratory grassland birds in northern New York State, USA. The ability of V. rossicum to dominate the woodland herbaceous layer raises concerns about forest regeneration.

V. rossicum is allelopathic and a number of compounds identified in the roots and fruits have anti-fungal and anti-feedant activity (ISSG, 2016). These compounds may inhibit the germination seeds and modify soil microbial communities on which sensitive plant species may depend upon (ISSG, 2016).

Impact on Biodiversity

Both V. nigrum and V. rossicum may have negative impacts on the reproduction of the Monarch butterfly, Danaus plexippus, as empty eggs have been found in the field. Experiments in field cages and in the laboratory indicate that larvae hatched from eggs oviposited on stems die in early instar stages (Casagrande and Dacy, 2001; DiTommaso and Losey, 2003). V. rossicum also displaces the native host for this species, Ascelpias syriaca (ISSG, 2016). A study by Ernst and Cappuccino (2002) found that monotypic stands of V. rossicum have been reported as decreasing insect biodiversity compared with graminoid old-fields or stands of Solidago altissima.

In North America, alvar habitats, disjunct and perhaps relict prairie plant communities on shallow soils over limestone bedrock are under competitive pressure from V. rossicum, as are populations of the USA federally listed hart's tongue fern, Phyllitis scolopendrium var. americana [Asplenium scolopendrium var. americanum].

Threatened Species

Social Impact

Large infestations of V. rossicum have interfered with management of, and access to, amenity areas. Loss of plant diversity, pastures, etc. on private lands has diminished pleasure and productivity of landowners.

Risk and Impact Factors

Impact mechanisms

• Competition - monopolizing resources
• Pest and disease transmission

Impact outcomes

• Damaged ecosystem services
• Ecosystem change/ habitat alteration
• Negatively impacts agriculture
• Negatively impacts animal health
• Negatively impacts tourism
• Reduced amenity values
• Reduced native biodiversity

Invasiveness

• Has high reproductive potential
• Has propagules that can remain viable for more than one year
• Highly adaptable to different environments
• Highly mobile locally
• Proved invasive outside its native range
• Tolerates, or benefits from, cultivation, browsing pressure, mutilation, fire etc

Likelihood of entry/control

• Difficult/costly to control
• Highly likely to be transported internationally accidentally
• Highly likely to be transported internationally deliberately

Uses

Several Vincetoxicum species were investigated as rubber substitutes during World War II by the Canadian Department of Agriculture however there is little information is available. V. rossicum was originally introduced for its ornamental purposes. Wreaths made with mature V. rossicum vines have been offered for sale in northern New York State, USA.

Similarities to Other Species/Conditions

V. rossicum may be confused with a number of closely related species in the genus Vincetoxicum.

In North America V. rossicum is often confused with V. nigrum, where ranges only occasionally overlap. Flowers and fruits of V. nigrum tend to be larger than those of V. rossicum, with the fruits 5-7 cm long. V. nigrum flowers are dark purple with straight white hairs on the upper surface, peduncles 1-3 cm.

In Europe, V. hirundinaria has yellow-white flowers and only occasionally twines. V. fuscatum has brown flowers with short, erect stems. Lack of taxonomic agreement, numerous subspecies and evidence of hybridization all add to confusion between species.

Prevention and Control

Cultural Control

V. rossicum has been suppressed in cattle pastures in central New York State, USA.

Mechanical Control

Mowing, pulling and other top destruction methods have poor long-term success as there is rapid regrowth from perennating buds. Effective timing of cutting, as fruit begin to enlarge, will prevent maturation of the seed crop and prevent successful recovery to form a new seed crop. Digging must remove the entire root crown.

Chemical Control

Triclopyr has been more effective at reducing V. rossicum than has glyphosate (Lawlor and Raynal, 2002). A systemic herbicide must be used against this perennial plant.

Biological Control

Possibilities for biological control of V. rossicum and V. nigrum are being investigated (Tewksbury et al., 2002). Host-range studies at the University of Rhode Island (URI), USA,  with Chrysolina aurichalcea ssp. asclepiadis have shown that this species is unsuitable age owing to the potential risk of attack on native North American Asclepias and Asteraceae (Weed and Casagrande, 2011).

In contrast, host-specificity tests conducted with more than 80 test plant species showed that the leaf-feeding moths Hypena opulenta and Abrostola asclepiadis are very host specific: successful larval development occurred only on species of Vincetoxicum. In 2014, mature H. opulenta larvae and pupae were successfully released on V. rossicum in Ottawa, Canada and released on V. nigrum in 2016. In 2016, H. opulenta had not yet been approved for release in the USA. Work on Chrysochus asclepiadeus did not show high levels of host specificity as for the two leaf feeding moths. Comparative host specificity studies are planed with various populations of C. asclepiadeus. Preliminary studies with the fruit fly Euphranta connexa indicate high host specificity. The potential of pathogens for biological control of V. rossicum has not yet been investigated. The chemical signature of Old World Asclepiadaceae may separate Vincetoxicum spp. from Asclepiadaceae species of the New World for effective host specificity.

IPM

Prevention and early eradication are the best control methods for V. rossicum. Seed crops from upwind infestations must be managed to successfully prevent new infestations. Early detection and eradication are essential. Public education will build awareness in susceptible areas.

References

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Contributors

28/12/2016 Updated by:

André Gassmann, CABI-CH, Switzerland

Distribution Maps

• = Present, no further details
• = Evidence of pathogen
• = Widespread
• = Last reported
• = Localised
• = Presence unconfirmed
• = Confined and subject to quarantine
• = See regional map for distribution within the country
• = Occasional or few reports

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