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Baccharis spicata (Asteraceae)

 

Why
Baccharis spicata (Asteraceae) is a medium sized shrub native to South America.  In 2015 two naturalised populations were recorded for the first time in the vicinity of Porto (Matosinhos and Vila do Conde) in Portugal (EPPO RS 2017/070).  Since these observations, four additional populations have been recorded with the most northern and southern populations some 30 km apart.  B. spicata has a wide climatic tolerance and can colonise a variety of habitats.  Coupled with high seed production which are wind-dispersed, B. spicata has the potential of becoming an emerging invasive species in the EPPO region. 

Geographical distribution
EPPO Region: Portugal.
South America: Argentina, Brazil, Paraguay, Uruguay.

Baccharis spicata
Courtesy: Rob Tanner

Morphology
B. spicata is a dioecious medium sized shrub usually 40-150 cm in height (maximum 300 cm).  Stems are unwinged and branch from the base.  The lower leaves are opposite with the upper leaves sub-opposite to alternate.  The species is capable of reproducing after 12 months.  Inflorescences are terminal and composed of cylindrical spikes. Flower heads are sessile and solitary or grouped in small glomerules.  The achenes bear a pappus which aids wind-dispersal.

Biology and ecology
Both male and female plants are present in Portugal.  Seed production and dispersal rates are similar to that of the congener B. halimifolia (EPPO A2 List -  EU List of Union concern), indicating that B. spicata also has the potential for long distance dispersal. 

Habitats
In its native range, B. spicata is reported to exhibit a high level of plasticity for suitable habitats.  It can grow in steppe and grasslands, disturbed coastal areas, river margins, arable land, abandoned paddies and urban areas.  In the EPPO region, in Portugal, the species is found on disturbed habitats colonised by other invasive non-native plant species. 

Invaded habitats (left: together with Cortaderia selloana) - Courtesy: Rob Tanner

Pathways for movement
Three Baccharis species are grown in European gardens - B. magellanica, B. patagonica and B. halimifolia.  However, there is no evidence that B. spicata is or has been grown as an ornamental species in the region.  The two originally identified populations in Portugal are located in the vicinity of an international airport and seaport, and thus accidental introduction is the most likely pathway of entry for these populations.

Impacts
In Portugal, B. spicata grows on disturbed ground with other highly invasive species such as Acacia longifolia, A. melanoxylon, Cortaderia selloana and Paspalum dilatatum.  In these habitats, B. spicata shows strong competition with other species becoming an abundant species in the community.

Control
The populations in Portugal represent the first naturalised record of the species outside its native range and thus there is little information on control options for the species. An EPPO National Regulatory Control Standard is available for B. halimifolia (PM 9/23 (1) Baccaris halimifolia), and some management methodologies detailed may be suitable for B. spicata.

Sources
EPPO (2016) First report of Baccharis spicata in Portugal. EPPO Reporting Service 2017 no. 3. Available at: https://gd.eppo.int/reporting/article-6038.
Verloove F, Dana ED, Alves P (2017) Baccharis spicata (Asteraceae), a new potentially invasive species to Europe. Plant Biosystems http://dx.doi.org/10.1080/11263504.2017.1303001

 

EPPO RS 2017/125
Entry date 2017-06

 

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