Conyza bonariensis (hairy fleabane)

Conyza bonariensis (hairy fleabane)
Herb up to 60 cm, greyish-green, with flowers arranged in small off-white spherical flower heads.
Scientific name: Conyza bonariensis (L.) Cronq.
Common names: hairy fleabane, Argentine fleabane, fleabane
Family: Asteraceae (Compositae)
Status in Portugal: invasive species (listed in the annex I of Decreto-Lei n° 565/99, 21 December)
Risk Assessment score: (in development)
Synonymy: Erigeron bonariensis L., Erigeron linifolius Willd., Leptilon bonariense (L.) Small, Leptilon
linifolium (Willd.) Small
Last update: 09/07/2014
How to recognise it
Annual herb up to 60 cm, covered in short hairs that
confer a greyish-green tone to the plant; simple primary
stem with terminal panicles, posteriorly with long
branches that overtop the main axis.
Leaves: greyish, pillose on both surfaces; basal leaves
oblanceolate, entire or with 2-5 coarse lobes on each side;
upper leaves smaller, linear-oblong, entire and sessile.
Flowers: arranged in capitula whose involucral bracts are
densely hairy; ligules that are hard to observe (< 0,5 mm).
Fruits: dirty-white cypselas, each one with a pappus of 4-5 Close-up of the stem and leaves covered
mm diameter; (open) capitula with 8-15 mm diameter.
by hairs
Flowering: June to August.
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Conyza bonariensis (hairy fleabane)
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 bonariensis is distinguished from the other species of Conyza (Conyza canadensis, Canadian
fleabane, and Conyza sumatrensis, tall fleabane) for having a smaller plant syze and for having bigger and
denser capitula (on the fruit) with dirty-white cypselas. It is also the only species that presents the shorter
main axis overtopped by the lateral branches.
Characteristics that aid invasion
It propagates by seed, producing high amounts of seeds (2000 a 230000 seeds per plant) of reduced
persistence (2 to 3 years) and a graduated germination. The seeds are efficiently dispersed by the wind,
rapidly enhancing their distribution area.
ORIGIN AND DISTRIBUTION
Native distribution area
South America.
Distribution in Portugal
Mainland Portugal (all provinces), Azores
archipelago (all islands), Madeira archipelago
(islands of Madeira and Porto Santo).
Other places where the species is invasive
Europe (Spain, France, Italy, Croatia, Greece, Malta,
Albania, Czech Republic), South Africa, Australia,
New Zealand, Oriental Africa, North America
(Mexico and USA), Central America.
Introduction reasons
Probably accidental, very ancient.
Preferential invasion environments
A ruderal weed species, very frequent in disturbed areas: urban areas, roadsides and crop fields or
common lands. It also appears in natural and semi-natural areas (e.g., dunes) normally associated to
disturbance events.
IMPACTS
Ecological impacts
It forms dense areas that prevent the growth of native vegetation.
Economic impacts
High costs in applying control methodologies, mainly in crop areas.
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Conyza bonariensis (hairy fleabane)
It reduces productivity in crop fields.
Other impacts
Due to the high production of pollen, it is considered an allergenic plant.
CONTROL
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 bonariensis include:
Physical control (preferential methodology)
Hand pulling: it is applied to plants of all sizes. In more compacted substrates, hand pulling should be
made during the rainy 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.
Continued use of this herbicide has recently originated the appearance of several biotopes of Conzya that
are resistant to it. However, as long as properly used, the herbicide application constitutes an effective
way to reduce invasion.
For additional information, visit the webpage www.invasoras.pt and/or contact us at [email protected].
REFERENCES
Alves P, Aguiar C (2012) Três neófitos novos para a Flora de Portugal. Silva Lusitana 20(1-2): 136-138.
CABI (2012) Conyza bonariensis. In: Invasive Species Compendium. CAB International, Wallingford, UK. Available:
www.cabi.org/isc [Retrieved 10/11/2012].
Dana ED, Sanz-Elorza M, Vivas S, Sobrino E (2005) Especies vegetales invasoras en Andalucía. Consejería de Medio Ambiente,
Junta de Andalucía, Sevilla, 233pp.
Dufour-Dror J-M (2012) Alien invasive plants in Israel. The Middle East Nature Conservation Promotion Association, Ahva,
Jerusalem, 213pp.
INRB (2011) Hairy fleabane - Conyza bonariensis resistente ao glifosato. Boletim técnico. UIPP-BT/09.
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.
Silva L, Corvelo R, Moura M, Carvalho JA, Land EO (2008) Conyza bonariensis (L.) Cronq. 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. 291-293.
USDA, NRCS (2012) The PLANTS Database. National Plant Data Team, Greensboro, NC 27401-4901 USA. Available: http://
plants.usda.gov [Retrieved 10/11/2012].
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