Stachytarpheta cayennensis (blue snakeweed)
Datasheet Types: Invasive species, Pest
Abstract
This datasheet on Stachytarpheta cayennensis covers Identity, Overview, Distribution, Dispersal, Hosts/Species Affected, Diagnosis, Biology & Ecology, Environmental Requirements, Impacts, Uses, Prevention/Control, Further Information.
Identity
- Preferred Scientific Name
- Stachytarpheta cayennensis (Rich.) Vahl
- Preferred Common Name
- blue snakeweed
- Other Scientific Names
- Stachytarpheta australis Moldenke
- Stachytarpheta dichotoma (Ruiz Lopez & Pavon) Vahl
- Stachytarpheta urticaefolia (Salisb.) Sims
- Valerianoides cayennensis (Rich.) Kuntze
- Verbena cayennensis Rich.
- International Common Names
- Englishblue porterweedblue rat's tailbluetopbranched porterweedbrazilian teacayenne porterweedcayenne snakeweedfalse verbenajoeenettleleaf porterweednettleleaf velvetberrynettleleaf vervainrattailrough leaved false vervain
- Frenchherbe à chenilleherbe bleuequeue de rat
- Local Common Names
- piche de gatorabo de zorro
- Brazilgervâogervao-urticante
- Cook Islandstiaki
- Fijifinak ne puaklaveniase karakarawaserakawatumbutumbuturulakaka
- French Polynesiapiripiri
- Japanhonagaso
- Kiribatite uti
- Micronesia, Federated states ofouchungsakura
- Nauruedidubaiedidubaiy
- Niuemautofu samoamotofu
- Palaulouch beluu
- Samoafua pepefua pepemautofumautofu talamautofu vaotaiotivao pepe
- Tonga‘i kuma‘iku ‘i kumahiku ‘i kuma
- USA/Hawaiioiowi
- EPPO code
- STCHI (Stachytarpheta cayennensis)
Pictures
Summary of Invasiveness
S. cayennensis is a shrub native to South and Central America and the Caribbean. It was introduced widely introduced into several tropical countries around the world as an ornamental species due to its attractive blue flowers, but in some countries it has become invasive. S. cayennensis has a wide environmental tolerance and often invades disturbed areas where it can outcompete native flora. It is invasive in many Pacific islands and is regarded as a noxious weed in the Northern Territory, Australia and is increasing in abundance in Florida, USA. According to a risk assessment this species is regarded as being highly invasive (score 20 = high risk) (PIER, 2015).
Taxonomic Tree
Notes on Taxonomy and Nomenclature
S. cayennensis belongs to the Verbenaceae family which comprises around 100 genera. The genus Stachytarpheta has undergone a series of taxonomic revisions that are further complicated by putative hybrids (Wilson et al., 2009). A total of 32 synonyms of S. cayennensis, including varieties, have been reported (The Plant List, 2013). Further details of the taxonomic history can be found in Munir (1992).
A number of species within the genus Stachytarpheta are also known to be invasive weeds.
Stachy(s) (a spike, originally an ear of corn) describes the elongate inflorescence, and tarphy (thick) refers to the thickened or densely flowered flower stalks. The plant was named after the capital of French Guiana, Cayenne.
The genus Stachytarpheta contains about 65 species, mostly from the American tropics. Many of which are regarded as being weedy throughout the tropics and subtropics. The closely related species S. jamaicensis is similar in appearance to S. cayennensis and the common names for these species are often used interchangeably.
Plant Type
Perennial
Broadleaved
Seed propagated
Shrub
Description
S. cayennensis is a perennial evergreen herb or subshrub which can reach heights of 2.5 m. It has a woody glabrous stem with several branches. Leaves opposite, membranous, elliptic to broadly elliptic or ovate, 4-8 cm long, 2-4.5 cm wide, upper surface rugose, both surfaces glabrous or occasionally lower surface with a few scattered hairs usually along the veins and margins, margins sharply and coarsely serrate, the teeth conspicuously divergent, apex acute, base cuneate, petioles 0.5-2 cm long. Spikes slender, rachis flexuous to erect or somewhat nodding, 14-40 cm long, ca. 2.5 mm in diameter, the furrows somewhat shallow, nearly as wide as the rachis, bracts lanceolate, ca. 7 mm long; calyx ca. 7 mm long, the teeth subequal; corolla usually dark purplish blue with a paler center, the tube 7-8 mm long (Wagner et al., 1999).
Distribution
The native range of S. cayennensis includes much of the Americas, from Mexico, Central America and the Caribbean, through tropical South America to southern Brazil (Weeds of Australia, 2011).
This species has been introduced into all of the continents with tropical and subtropical climates between 30° N and 30° S parallels.
Distribution Map
Distribution Table
History of Introduction and Spread
The majority of introductions throughout the world are as a result of intentional introductions for ornamental purposes. S. cayennensis produces an attractive blue flower which is appealing to bees and butterflies.
In 1868 S. cayennensis was introduced into New Caledonia as fooder for livestock (Blanfort et al., 2008).
Risk of Introduction
The risk of S. cayennensis being introduced into new areas is fairly high as seeds of this species are readily available for sale on the internet. In addition to this, it can disperse locally by winds, attachment of seeds to vehicles and animals or as a contaminant in hay (Weeds of Australia, 2011). A risk assessment conducted by PIER (2015) gave this species a high score of 20 and therefore would reject its import due to its invasive tendencies.
Means of Movement and Dispersal
Natural Dispersal
Seeds of S. cayennensis may be dispersed over short distances by rain and run-off. There is some indications that this species may reproduce and spread locally by vegetative propagation (PIER, 2015).
Vector Transmission
Seeds of this species may become attached to the fur of animals and translocated over short distances into new areas (Weeds of Australia, 2011).
Accidental Introduction
It is believed that the spread of this species in Queensland, Australia is a result of accidental introductions via fodder, hay and contaminated pasture seed (Smith, 2002). Seeds may also be introduced into new areas in garden waste or by attachment of seeds to clothing, vehicles and machinery (Weeds of Australia, 2011).
Intentional Introduction
S. cayennensis was intentionally introduced into a number of countries as an ornamental species. This species produced an attractive blue flower which is appealing to bees and butterflies. Seeds of this species are still readily available for sale on the internet.
Pathway Causes
Pathway cause | Notes | Long distance | Local | References |
---|---|---|---|---|
Garden waste disposal (pathway cause) | Yes | |||
Internet sales (pathway cause) | Several companies sell seeds for ornamental purposes | Yes | ||
Seed trade (pathway cause) | Yes |
Pathway Vectors
Pathway vector | Notes | Long distance | Local | References |
---|---|---|---|---|
Debris and waste associated with human activities (pathway vector) | Yes | |||
Land vehicles (pathway vector) | Yes | |||
Livestock (pathway vector) | Yes | |||
Soil, sand and gravel (pathway vector) | Yes | |||
Water (pathway vector) | Yes |
Hosts/Species Affected
S. cayennensis may outcompete smaller native plant species and crops dedicated to livestock are often affected by smothering. In Australia, this species is commonly found as a weed of pastures and sugarcane (Saccharum species) (DAFF, 2014).
Host Plants and Other Plants Affected
Host | Family | Host status | References |
---|---|---|---|
Theobroma cacao (cocoa) | Malvaceae | Unknown |
Similarities to Other Species/Conditions
Others species within the genus Stachytarpheta closely resemble S. cayennensis. These include S. jamaicensis, S. australis and S. mutabilis. The colour of the flower is often used to differentiate between the species. The flowers of S. jamaicensis are light blue or mauve, S. australis has light blue or white flowers and the stem and lower face of leaves are pubescent and S. mutabilis is characterized by having larger pink or red flowers with a hairy stem.
Hybridization between the closely related species S. cayennensis and S. jamaicensis may occur. The hybrids more closely resemble S. jamaicensis, but the corollas are darker in colour than typical in S. jamaicensis. The habit is more erect, and the leaves are usually more ovate, darker green and with more divergent teeth similar to S. cayennensis (Wagner et al., 1999). S. cayennensis may also hybridize with S. mutabilis. A number of hybrids have been found to have naturalized in Queensland (Weeds of Australia, 2011).
S. cayennensis is also similar in appearance to Verbena litoralis and V. officinalis however these have four stamens instead of two with smaller flowers which are less than 4 mm across (Weeds of Australia, 2011).
Habitat
S. cayennensis is common in open field like pastures, crop fields, moorlands, fallow lands, roadsides and wastelands. This species is also tolerant to shade and may invade low density forests. S. cayennensis grows on every type of soils, including infertile and dry soils. Although it can tolerate drought, this species grows best in moist, deep, fertile soils in disturbed areas (HEAR, 2012).
Habitat List
Category | Sub category | Habitat | Presence | Status |
---|---|---|---|---|
Terrestrial | ||||
Terrestrial | Terrestrial – Managed | Cultivated / agricultural land | Present, no further details | Productive/non-natural |
Terrestrial | Terrestrial – Managed | Managed forests, plantations and orchards | Present, no further details | |
Terrestrial | Terrestrial – Managed | Managed grasslands (grazing systems) | Present, no further details | Productive/non-natural |
Terrestrial | Terrestrial – Managed | Disturbed areas | Principal habitat | Natural |
Terrestrial | Terrestrial – Managed | Rail / roadsides | Present, no further details | Harmful (pest or invasive) |
Terrestrial | Terrestrial ‑ Natural / Semi-natural | Natural forests | Present, no further details | |
Terrestrial | Terrestrial ‑ Natural / Semi-natural | Natural grasslands | Principal habitat | Natural |
Terrestrial | Terrestrial ‑ Natural / Semi-natural | Scrub / shrublands | Present, no further details |
Climate
Climate type | Description | Preferred or tolerated | Remarks |
---|---|---|---|
A - Tropical/Megathermal climate | Average temp. of coolest month > 18°C, > 1500mm precipitation annually | Preferred | |
Af - Tropical rainforest climate | > 60mm precipitation per month | Preferred | |
As - Tropical savanna climate with dry summer | < 60mm precipitation driest month (in summer) and < (100 - [total annual precipitation{mm}/25]) | Tolerated | |
Aw - Tropical wet and dry savanna climate | < 60mm precipitation driest month (in winter) and < (100 - [total annual precipitation{mm}/25]) | Tolerated | |
Cf - Warm temperate climate, wet all year | Warm average temp. > 10°C, Cold average temp. > 0°C, wet all year | Tolerated | |
Cs - Warm temperate climate with dry summer | Warm average temp. > 10°C, Cold average temp. > 0°C, dry summers | Tolerated | |
Cw - Warm temperate climate with dry winter | Warm temperate climate with dry winter (Warm average temp. > 10°C, Cold average temp. > 0°C, dry winters) | Tolerated |
Latitude/Altitude Ranges
Latitude North (°N) | Latitude South (°S) | Altitude lower (m) | Altitude upper (m) |
---|---|---|---|
30 | 30 |
Soil Tolerances
Soil texture > light
Soil texture > medium
Soil texture > heavy
Soil reaction > acid
Soil reaction > neutral
Soil reaction > alkaline
Special soil tolerances > saline
Special soil tolerances > infertile
Impact Summary
Category | Impact |
---|---|
Economic/livelihood | Negative |
Environment (generally) | Negative |
Human health | Positive |
Impact: Environmental
Impact on Habitats
S. cayennensis is unpalatable to livestock and in areas with heavy grazing this species may outcompete surrounding species (HEAR, 2013).
Impact on Biodiversity
This species is opportunistic and can readily invade disturbed areas. It can form dense thickets which may outcompete or smother native plant species (PIER, 2015). In Florida this species is regarded as a Category II plant, a species which has increased in abundance but has not yet altered plant communities (FLEPPC, 2009).
Risk and Impact Factors
Invasiveness
Proved invasive outside its native range
Highly adaptable to different environments
Pioneering in disturbed areas
Tolerant of shade
Impact outcomes
Reduced native biodiversity
Impact mechanisms
Competition - monopolizing resources
Competition - shading
Hybridization
Likelihood of entry/control
Highly likely to be transported internationally deliberately
Difficult to identify/detect in the field
Uses
Economic Value
There is no information available on the economic value of S. cayennensis. As an ornamental this species is sold in the nurseries and via the internet and therefore has some economic value.
Social Benefit
In Latin America, S. cayennensis is utilised in traditional medicine to treat symptoms of malaria, treat dysentery and liver disorders, to relieve fevers and to act as a sedative (Taylor, 2012). The plant contains flavonoids, terpenes, phenols and steroids and has been found to have anti-inflammatory and anti-malarial properties (Okoye et al., 2014).
Uses List
Environmental > Ornamental
Medicinal, pharmaceutical > Source of medicine/pharmaceutical
Animal feed, fodder, forage > Fodder/animal feed
Ornamental > Potted plant
Ornamental > Seed trade
Prevention and Control
Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.
Prevention
SPS Measures
In Australia, S. cayennensis is regarded as an environmental weed and regulations are in place in a number of territories to prevent its spread. In New South Wales this species is restricted, meaning that it cannot be sold or distributed within the territory. In the Northern Territroy this species has been declared a noxious weed. This means that the spread of this species must be controlled and that introductions are prohibited (Weeds of Australia, 2012).
S. cayennensis is included in a list of the 33 most invasive species of the South Pacific (Blanfort et al., 2008).
Control
Physical/Mechanical Control
Manual removal of seedlings by hand can be effective for small populations, ensuring the large roots are also removed. S. cayennensis may also be controlled by chipping or cultivation (ploughing, grubbing and hoeing) (Swarbrick, 1997). Planting of local and vigorous pasture plants, such as legumes, may compete with S. cayennensis and prevent re-establishment.
Biological Control
No biological control agents have been released for S. cayennensis, however possible agents are discussed by Waterhouse and Norris (1987). The potential for biological control of the closely related species S. jamaicensis is discussed in detail by Cock et al. (1985).
Chemical Control
It has been suggested that S. cayennensis is sensitive to foliar application of 2,4-D or MCPA (Motooka et al., 2003). It is however, less sensitive to other hormone type herbicides, although drizzle application of triclopyr in water have been found to be effective in trials in Palau (Motooka et al., 2003). Some control using glyphosate has been recorded. The best control of S. cayennensis can be achieved during the summer months when plants are actively growing (Weeds of Australia, 2011).
IPM
For large areas of S. cayennensis it is recommended that plants are mechanically removed and treated with herbicides. The best time to cut plants is before flowering. It is necessary to follow up and retreat areas with herbicides to provide effective control (Weeds of Australia, 2011).
Links to Websites
Name | URL | Comment |
---|---|---|
GISD/IASPMR: Invasive Alien Species Pathway Management Resource and DAISIE European Invasive Alien Species Gateway | https://doi.org/10.5061/dryad.m93f6 | Data source for updated system data added to species habitat list. |
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