Evergreen shrub or small tree, with bright yellow spikes; very frequent in coastal dunes.
Scientific name: Acacia longifolia (Andrews) Willd.
Common names: Sydney golden wattle, golden wattle
Family: Fabaceae (Leguminosae)
Status in Portugal: invasive species (listed in the annex I of Decreto-Lei n° 565/99, of 21 December)
Risk Assessment score: (in development)
Synonymy: Acacia longifolia (Andrews) Willd. var. typica Benth., Mimosa longifolia Andrews, Mimosa macrostachya Poiret, Phyllodoce longifolia (Andrews) Link Racosperma longifolium (Andrews) Martius
Last update: 30/06/2014
How to recognise it
Shrub or small tree up to 8 m.
Flowering: December to April.
Acacia cyclops (coastal wattle) is similar but has phyllodes that are generally smaller, lighter and slightly falcate; the flowers are arranged in globular flower heads, the pod is compressed and the funicle is scarlet and completely encircles the seed. Acacia melanoxylon (Australian blackwood) also has some similarity, but the phyllodes are falcate, the flowers are arranged in globular flower heads and the seeds are completely encircled by an orange funicle.
Characteristics that aid invasion
It reproduces by seed, producing many seeds that remain viable in the ground for many years. Seed production may reach 12000 seeds/m2/year, where most part accumulates underneath the tree. The seeds are dispersed by animals, mainly birds and ants, which lead to the formation of invasion foci. Germination is stimulated by fire. It presents a high growth rate.
The species also propagates vegetatively, forming shoots from the stump in some situations. However, in understory areas, under some climate conditions or seasons of the year, the species sprouts much less vigorously or may even not sprout.
Native distribution area
Distribution in Portugal
Mainland Portugal (Trás-os-Montes, Minho, Douro Litoral, Beira Litoral, Estremadura, Ribatejo, Alto Alentejo, Baixo Alentejo, Algarve), Madeira archipelago (islands of Madeira and Porto Santo).
Other places where the species is invasive
Europe (France, Spain, Italy), South Africa, New Zealand, South America (Brazil), Western USA (California), Asia (Israel).
For ornamental purposes and for erosion control, mainly in costal dunes.
Preferential invasion environments
Coastal dunes and watercourses. It also appears, although less frequently, along roadsides and over interior mountainous areas.
It is one of the invasive species that causes stronger impacts on dune ecosystems.
Impacts on ecossystems
It forms very dense populations inhibiting the development of native vegetation, diminishing the flow of watercourses.
It produces a lot of nitrogen-rich litter, which promotes change in soil composition (carbon and nutrients, mainly nitrogen) and microbiology.
Expensive control methods.
Natura 2000 Network habitats more subject to impacts
– Southern riparian galleries and thickets (Nerio-Tamaricetea and Securinegion tinctoriae) (92D0 pt1, pt2);
– Vegetated sea cliffs of the Atlantic and Baltic coasts (1230);
– Shifting dunes along the shoreline with Ammophila arenaria («white dunes») (2120);
– Fixed coastal dunes with herbaceous vegetation («grey dunes») (2130);
– Atlantic decalcified fixed dunes (Calluno-Ulicetea) (2150);
– Dunes with Salix repens ssp. argentea (Salicion arenariae) (2170);
– Wooded dunes of the Atlantic, Continental and Boreal region (2180);
– Humid dune slacks (2190); – Malcolmietalia dune grasslands (2230);
– Coastal dunes with Juniperus spp. (2250);
– Cisto-Lavenduletalia dune sclerophyllous scrubs (2260);
– Wooded dunes with Pinus pinea and/or Pinus pinaster (2270);
– Inland dunes with open Corynephourus and Agrostis grasslands (2330);
– Rivers with muddy banks with Chenopodium rubri p. p. and Bidention p. p. vegetation (3270).
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 Acacia longifolia include:
Hand pulling: preferential methodology for seedlings and small plants. When in more compacted substrates, hand pulling must be made during the rainy season as to facilitate the removal of the root system. It should be guaranteed that no stumps and main roots are left in the ground.
Cutting: preferential methodology for adult plants. Care should be taken to cut the trunk as close to the ground as possible by using manual and/or mechanical equipment. It should be done before seed maturation. Most times, this operation is enough for the effective control of the species. However, there are situations where the sprouting occurs after cutting, making necessary the application of this methodology in posterior interventions in combination with other methodologies, namely the application of herbicide.
Physical + chemical control
Cut stump method: Apply to adult plants. Cut the trunk as close to the ground as possible and immediately (in the following seconds) apply herbicide (active substance: glyphosate) to the cut stump. If shoots should latter on appear, these should be immediately eliminated when they reach 25 to 50 cm height by cutting or pulling.
The wasp Trichilogaster acaciaelongifoliae (Hymenoptera: Pteromalidae) is used with success in South Africa since 1982. This species forms galls on the floral and vegetative buds of A. longifolia inhibiting the formation of up to 90% of the seeds. Its use is combined with the weevil [Melanterius ventralis (Coleoptera: Curculionidae)] that feeds off the few remaining seeds that are formed.
OThe specificity tests, in quarantine, to evaluate the security in using T. acaciaelongifoliae in Portugal were officially authorized and concluded in 2010. Final authorization for liberation in the natural medium is being awaited.
It may be strategically used to favour germination of the seed bank, e.g., after the control of adult individuals (with the adequate management of the resulting biomass) and the subsequent elimination of seedlings. This method provides an advantageous reduction of the seed bank, both by destroying part of the seeds or by stimulating the germination of the remainders.
Visit the webpage How to Control for additional and more detailed information about the correct application of these methodologies.
Agricultural Research Council – Plant Protection Research Institute – Weed Research Division (2014) Management of invasive alien plants: A list of biocontrol agents released against invasive alien plants in South Africa. Available: http://www.arc.agric.za/arc-ppri/Documents/WebAgentsreleased.pdf [Retrieved 03/03/2014].
CABI (2012) Acacia longifolia. In: Invasive Species Compendium. CAB International, Wallingford, UK. Available: http://www.cabi.org/isc/ [Retrieved 06/11/2012].
Dennill GB, Donnelly D, Stewart K, Impson FAC (1999) Insect agents used for the biological control of Australian Acacia species and Paraserianthes lophanta (Willd.) Nielsen (Fabaceae) in South Africa. African Entomology: Memoir no.1: 45-54.
Marchante E, Freitas H, Marchante H (2008) Guia prático para a identificação de plantas invasoras de Portugal Continental. Imprensa da Universidade de Coimbra, 183pp.
Marchante E, Kjøller A, Struwe S, Freitas H (2008) Short- and long-term impacts of Acacia longifolia invasions on the belowground processes of a Mediterranean coastal dune ecosystem. Applied Soil Ecology 40: 210-217.
Marchante H, Freitas H, Hoffman JH (2010) Seed ecology of an invasive alien species, Acacia longifolia (Fabaceae), in Portuguese dune ecosystems. American Journal of Botany 97 (11): 1780-1790.
Marchante H, Freitas H, Hoffman JH (2011) The potential role of seed banks in the recovery of dune ecosystems after removal of invasive plant species. Appl Veg Sci 14: 107-119.
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