Short description of Nassella neesiana, American Needle-Grass

N. neesiana is an erect, perennial tussock forming grass that grows in dense clumps with culms up to 100cm tall. The inflorescence has a distinctive purplish colour and bears a loose panicle with sharp pointed (long-lived) seeds that are 8-10mm long and with hairy awns up to 90mm in length. Leaves are 10-30cm long, 1-5mm wide, and rough to the touch at the edges. The most distinctive feature of Chilean Needle-grass is the corona (ciliate on the margins) that is found at the join of the seed body and the awn.

Impact summary: Nassella neesiana, American Needle-Grass

N. neesiana has established, spread and become invasive in  Australia and New Zealand, is considered to be unpalatable in the summer months and can quickly dominate large areas of highly productive pasture land. It has the potential to flower year-round and outcompetes native vegetation, thereby reducing the biodiversity of native grasslands. Its seeds can cause injury to livestock if ingested. Plants are capable of producing seeds in the nodes and bases of the flowering stems. These seeds are self-fertilised (cleistogamous), account for about one quarter of total seed production, and enable the plant to reproduce despite attempted control via grazing or by burning (whch can lead to a monoculture of N. neesiana).

Habitat summary: Nassella neesiana, American Needle-Grass

In GB, it has been found in wasteground, rubbish tips and, rarely, inner-city environments.

Overview table

Environment	Terrestrial
Species status	Non-Native
Native range	Bolivia, Ecuador, Peru, Paraguay, Uruguay, Argentina, Chile, Southern Brazil
Functional type	Land plant
Status in England	Non-Native
Status in Scotland	Non-Native
Status in Wales	Non-Native
Location of first record	v.c.79
Date of first record	1916

Origin

It is native to South America, recorded from northern Argentina, Bolivia, Peru, Ecuador, Uruguay, Paraguay, southern Brazil and Chile.

First Record

1916

Pathway and Method

Initially introduced on wool with a first record of 1916. All GB records report casual occurrence – thus it is not currently spreading (or established).

Species Status

Reported as highly invasive in New Zealand and Australia, where it is abundant over large areas of New South Wales, the Australian Capital Territory and Victoria. Isolated populations have been found in South Australia and southern Tasmania. Also very occasionally found as a naturalised weed in the United States, GB, France, Italy and Spain.

Dispersal Mechanisms

A temperate species of warm, humid climates (500-800mm annual rainfall), tolerant to both drought and seasonal waterlogging and an early colonist of bare or disturbed ground. Its seeds are readily dispersed on farm animals (through becoming attached to wool, hides and animal carcases) and by grass-cutting operations on roadsides and sporting fields. Seeds may also be dispersed long distances by floodwaters, wild animals, as contaminants of seeds or fodder, the long-distance moving of livestock between farms or even the importation of infested hides to use in tanning works. However, seeds are poorly adapted for natural dispersal by wind.

Reproduction

Reproduction is by seed (from chasmogamous and cleistogamous flowers), which can have up to 90% viability and build up a long term (at least 12 years) persistent seed bank. Seeds germinate mainly in the autumn and spring, and although seedlings are slow-growing, they have a high survival rate. Plants can flower and set seed in the first season, and a single plant may produce as many as 22,000 seeds per square metre.

Known Predators/Herbivores

None known.

Resistant Stages

None known.

Habitat Occupied in GB

 Wasteground, rubbish tips, inner city paving.

South America (see above for native distribution), GB, USA, France, Spain (mainland and Canary Islands), Italy (mainland near Genoa and Corsica), Australia, New Zealand.

Environmental Impact

Where N. neesiana has established and spread (e.g. Australia, New Zealand), it is considered to be unpalatable in the summer months and can dominate large areas of highly productive pasture land and grassy woodland, and also the margins of streams and riverbanks. It outcompetes native vegetation, thereby reducing the biodiversity of native grasslands, and its seeds can cause serious injury to livestock if ingested. Plants are capable of producing seeds in the nodes and bases of the flowering stems. These seeds are self-fertilised (cleistogamous), account for about one quarter of total seed production, and enable the plant to reproduce despite grazing or attempted control by burning (which has been shown to eventually lead to a dominace of the species via rapid germination of the seed bank).

Health and Social Impact

Loss of income for livestock farmers via dominace of a grass that is not palatable in the summer months.

Economic Impact

In Australia, on average, N. neesiana costs from $64.50 ha-1 to $118.75 ha-1 to control on grazing lands, depending on whether the infestation is scattered or dense.

Identification

Walsh, N. (1998) Identification of South American Tussock Weeds. Plant Protection Quarterly 13 (2): 59-62.

Cope, T. & Gray, A. (2009) Grasses of the British Isles. BSBI Handbook no. 13. BSBI, London.

Stace, CA. (2010) New Flora of the British Isles: Ed 3. Cambridge University Press, Cambridge.http:weeds.dpi.nsw.gov.auWeedsDetails36http:keyserver.lucidcentral.orgweedsdata080c0106-040c-4508-8300-0b0a06060e01mediahtmlNassella_neesiana.htm

Biology, ecology, spread, vectors

Anderson, F.E., et al. (2010) Investigations into biological control of Nassella neesiana in Australia and New Zealand. In Proceedings of the 17th Australasian Weeds Conference (ed Zydenbos, S.M.) pp. 215–218. New Zealand Plant Protection Society, Christchurch, New Zealand.

Anderson, F.E., et al. (2011) Biological control of Chilean Needle-grass (Nassella neesiana) in Australasia: Completion of host range testing. In XIII International Symposium on Biological Control of Weeds. pp. 26-32.

Bourdôt, G.W. & Hurrell G.A. (1992) Aspects of the ecology of Stipa neesiana Trin. and Rupr. seeds. New Zealand Journal of Agricultural Research 35: 101–108.

Bourdôt, G.W., et al. (2012) The potential global distribution of the invasive weed Nassella neesiana under current and future climates. Biological Invasions 14: 1545-1556.

Management and impact

Anonymous (2003) Weed management guide—Chilean needle-grass (Nassella neesiana). Retrieved from http:www.weeds.gov.aupublicationsguidelineswonspubsn-neesiana.pdf on 14 December 2015.

General

Agriculture and Resource Management Council of Australia and New Zealand, Australian and New Zealand Environment and Conservation Council and Forestry Ministers (2003). Weeds of National Significance, Chilean needle grass (Nassella neesiana) strategic plan, National Weeds Strategy Executive Committee, Launceston.

Csurhes, S. (2008) Pest plant risk assessment: Chilean Needle-grass Nassellia neesiana. Unpublished report for the Department of Primary Industries and Fisheries, Queensland Government, Australia.McLaren, DA, Stajsic, V & Gardener, MR (1998), ‘The distribution and impact of SouthNorth American stipoid grasses (Poaceae: Stipeae) in Australia’, Plant Protection Quarterly 13: 62–70.

McLaren, DA, Tereso, AM & Weiss, J (2002), ‘Distribution, economic impact and attitudes towards Chilean needle grass (Nassella neesiana (Trin. and Rupr.) Barkworth) in Australia’, Proceedings of the 13th Australian Weeds Conference, pp. 749–52.