conyza sumatrensis

Conyza sumatrensis

Herb up to 200cm, with flowers arranged in small off-white spherical flower heads.

Scientific name: Conyza sumatrensis (Retz.) E. Walker

Common names: tall fleabane, broad-leaved fleabane, fleabane

Family: Asteraceae (Compositae)

Status in Portugal: invasive species

Risk Assessment score: (in development)

Synonymy: Conyza albida Sprengel, Conyza albida Willd. Ex. Spreng.

Last update: 09/07/2014

pormenor sumatrensis

Close-up of capitula of Conyza sumatrensis: in flowering (left); in frutification (right).

 

 

How to recognise it

Annual herb up to 200 cm, with a robust look.

Leaves: greyish-green, densely hairy; the inferior leaves are lanceolate with indented margins; the upper leaves are linear-lanceolate, with entire margins.

Flowers: arranged in capitula whose involucral bracts are densely hairy; very small ligules, hardly noticeable to the naked eye.

Fruits: off-white cypselas, with a pappus of 3 mm diameter; capitula (open) with 4-8(10) mm diameter.

Flowering: June to August.

 

Similar species

The several Conyza species in Portugal are very similar and hard to distinguish. Additionally, the Conyza species hybridize very rapidly among themselves, originating hybrids with intermediate characteristics, causing further difficulty in the identification.

Conyza sumatrensis is distinguished from the Conyza bonariensis (hairy fleabane) by having a larger plant type (C. sumatrensis up to 200 cm; C. bonariensis up to 60 cm) and smaller open capitula (C. sumatrensis 4-8 mm; C. bonariensis 8-15 mm).

It may be distinguished from Conyza canadensis (Canadian fleabane) for having involucral bracts and densely hairy leaves (while C. canadensis has no hairs on the involucral bracts and the leaves have cilia only on the margin and on the midrib) and absence of well visible ligules.

Comparison of capitula

Close-up of capitula: comparison of the three most common Conyza species in Portugal

Characteristics that aid invasion

It propagates by seed, producing a high amount of seeds that are efficiently dispersed by the wind, rapidly enhancing their distribution area.

 

 

Native distribution area

South America.

 

Distribution in Portugal

Mainland Portugal (all provinces), Madeira archipelago (Madeira island).

Geographic areas where there are records of Conyza sumatrensis

Other places where the species is invasive

Europe (Spain, France, Romania, Yugoslavia, United Kingdom).

 

 Introduction reasons

Probably accidental, very ancient.

 

Preferential invasion environments

A ruderal weed species, very frequent in disturbed areas: urban areas, roadsides and croplands or common lands. It also appears in natural and semi-natural areas (e.g., dunes) normally associated to disturbance events.

 

 

Impacts on ecossystems

It forms dense areas that prevent the growth of native vegetation.
 

Economic impacts

High costs in applying control methodologies, mainly in crop areas.

It reduces productivity in crop fields.
 

Other impacts

Due to the high production of pollen, it is considered an allergenic plant.

 

 

Controlling an invasive species demands a well-planned management, which includes the determination of the invaded area, identifying the causes of invasion, assessing the impacts, defining the intervention priorities, selecting the adequate control methodologies and their application. Afterwards it is fundamental to monitor the efficiency of the methodologies and recuperation of the intervened area as to perform, whenever necessary, the follow-up control.

The control methodologies used for Conyza sumatrensis include:

 

Physical control (preferencial methodology)

Hand pulling: it is applied to plants of all sizes. In more compacted substrates, hand pulling should be made during the rainy as to facilitate the removal of the root system.

Agricultural practices of soil mobilization (tilling, harrowing): it is applied to plants of all sizes when dense infestations occur. It should be done before flowering.

 

Chemical control

Foliar application of herbicide. Spray with herbicide (active substance: glyphosate) limiting as much as possible its application to the target species. The herbicide application should be done during the early stages of the plant’s development, before the primary axis is developed.

 

Visit the webpage How to Control for additional and more detailed information about the correct application of these methodologies.

 

Alves P, Aguiar C (2012) Três neófitos novos para a Flora de Portugal. Silva Lusitana 20 (1-2): 136-138.

CABI (2012) Conyza sumatrensis. In: Invasive Species Compendium. CAB International, Wallingford, UK. Available: http://www.cabi.org/isc/ [Retrieved 10/11/2012].

Carvalho JA (2008) Conyza sumatrensis (Retz.) E. Walker In: Silva L, Land EO, Luengo JLR (eds) Flora e fauna terrestre invasora na Macaronésia. Top 100 nos Açores. Madeira e Canárias. Arena, Ponta Delgada, pp. 478-480.

Dana ED, Sanz-Elorza M, Vivas S, Sobrino E (2005) Especies vegetales invasoras en Andalucía. Consejería de Medio Ambiente, Junta de Andalucía, Sevilla, 233pp.

Flora Digital de Portugal (2012) Conyza sumatrensis. Available: http://jb.utad.pt/especie/conyza_sumatrensis [Retrieved 10/11/2012].

Marchante E, Freitas H, Marchante H (2008) Guia prático para a identificação de plantas invasoras de Portugal Continental. Imprensa da Universidade de Coimbra, Coimbra, 183pp.

 

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