Chilean needle grass (Nassella neesiana)

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Impact

Chilean needle grass is closely related to serrated tussock (Nassella trichotoma). Chilean needle grass affects both sown pasture and native grasslands of southeastern Australia. It is relatively unpalatable and reduces farm productivity by displacing more desirable pasture species. Heavy infestations can decrease productivity by as much as 50% during summer. It also causes injury to stock and downgrades wool, skins and hides with its long, sharp seeds.

Research on the Northern Tablelands of NSW by the University of New England has shown that the main reason for the success of Chilean needle grass is its large, long-lived reserve of viable seed in the soil seed bank. This seed bank can persist for many years even if further seed input is prevented. It is a prolific seeder, with the potential to produce more than 20,000 seeds per square metre in a good season. It also has hidden seeds under the leaf sheaths at each of the nodes on the flowering stems that mature even if the seed head has been removed. 

Distribution

Chilean needle grass is a serious weed on the Northern Tablelands and north-west slopes of New South Wales. According to records at the National Herbarium, it was first identified in NSW during the early 1940s in the Glen Innes region.

It is thought to have spread very slowly until the late 1970s. Identifications of this species from the Guyra - Glen Innes area since the mid 1970’s have increased indicating its ability to spread. In 1996 a major infestation was identified near Tamworth in the Reedy Creek catchment. Chilean needle grass is also well established on the Southern Tablelands and southwest slopes of NSW and in southern and central Victoria.

Chilean needle grass is a native of South America occurring in Argentina, Uruguay, Chile and Brazil. It has become naturalised in New Zealand, South Africa and several European countries. In Australia, Chilean needle grass is considered a weed because it is very invasive and is less productive/lower quality than introduced pasture, causing a reduction of carrying capacity. 

Distribution map

Spread

Chilean needle grass germinates in autumn and spring and at other times of the year given adequate moisture and temperature. The seedling grows quite slowly but has a very high survival rate and can produce flowers in the first season. The adult plant is long-lived and very hardy, surviving heavy grazing and drought.

Seed heads emerge during late spring, and when mature have a very distinctive purplish colour. The individual seeds are very sharp at the apex (hence the name). By late February, most of the seed has been shed from the plant and can be found on the ground. Wind dispersal of seed appears to be almost negligible. Most of the spread is by attachment to animals (both domestic and wildlife) or machinery, particularly motor vehicles. The backward pointing hairs on the apex of the seed anchor firmly in the wool of sheep. These seeds may fall from the fleece several months later, spreading the seed to new regions. Sometimes, Chilean needle grass seed will penetrate the skin of sheep reducing their hide value and may irritate individual animals.

Description

Chilean needle grass appears very similar to the native spear grasses (Austrostipa spp.). The most diagnostic feature of Chilean needle grass (and only found in this species) is the corona — a raised crown of small teeth, at the junction of the seed body and the seed awn. The awn twists when dry and often has two bends in it.

Vegetative (green leafy) plants of Chilean needle grass can be mistaken for many other winter green species, especially Danthonia and fescue. Close examination reveals the presence of hairs along the leaf surface of Chilean needle grass by contrast with the hairless leaves of fescue and the much coarser feel of needle grass leaves compared with Danthonia. Chilean needle grass also has a small tuft of hairs at the junction of the leaf blade and the leaf sheath, which most other grasses do not have.

Chilean needle grass forms a robust tussock but is variable and not as clumpy as Poa or many Eragrostis species. 

Habitat

The main requirement for establishment of Chilean needle grass is bare ground that can be created by over grazing or indiscriminate herbicide application. 

Acknowledgements

Authors: A. M. Storrie and J. C. Lowien

Editor: Bill Noad

Technical reviewers: Dr Mark Gardener, M. Duncan and M. Michelmore

Other publications

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Control

Once established in an area and allowed to set seed, it is unlikely Chilean needle grass can be eradicated. This is because established populations have a persistent seed bank that will enable reinfestation even if adult plants have been killed. Small newly establishing infestations may be eradicated with a great deal of persistence.

The management options of established Chilean needle grass populations depend on the land use. These options include crop rotation, pasture sowing, herbicide control and grazing management with best results where a combination of options is used. The management goals should aim to reduce the soil seed bank and minimise the Chilean needle grass component of the pasture by creating conditions that hinder its growth. The most important of these conditions is the maintenance of good ground cover through competitive perennial pastures and grazing management.

Arable areas

On arable lands timely planting of crops can keep Chilean needle grass populations to a minimum. Where ploughing is possible, planting a sequence of fodder crops for two or three years will reduce the weed seed bank. However seeds buried as a result of deep cultivation will remain viable for longer periods than those near the surface.

Winter or summer forage cropping or summer grain cropping programs can be used. The important issue with any of the cropping programs is to make sure that any seedlings that germinate and go through winter are prevented from flowering and seeding in late spring/early summer either by chemical, cultivation or very heavy grazing.

Following the cropping phase establishment of a perennial pasture will provide competition for remaining Chilean needle grass seedlings. The pasture must be allowed to properly establish and maintain good ground cover all year-round and develop height plus bulk from November to February to have a smothering effect against Chilean needle grass seedlings. In addition, regular paddock inspection and spot spraying to eliminate newly emerged plants is vital to maintain clear areas.

Non-arable areas

The same principles apply as those for arable areas. The seed bank should be reduced by a succession of short-term pasture or annual fodder crops established by direct drilling. In many locations, steep or stony country causes great difficulty, even for direct drilling. In these areas, aerial application of herbicide, seed and fertiliser would be necessary, but, where possible, ground application of herbicide is preferred to reduce off-target damage.

Pasture management of these areas is vital to ensure plenty of competition to needle grass seedlings. Strategic grazing and resting of pasture should aim to maintain comprehensive ground cover, particularly during spring and autumn germination of Chilean needle grass seeds.

For specific pasture species and management recommendations for your area refer to the appropriate pasture management guides.

Grazing management

One inexpensive and adaptable tool available to most landholders is grazing management. Although Chilean needle grass is less palatable than other introduced pasture plants, research has shown that during winter it produces a reasonable quantity of average quality feed (up to 16.6% crude protein and digestibility of approximately 60% — in comparison the temperate pasture grass fescue had crude protein up to 18.8% and digestibility of approx. 65%). In extensive areas of Chilean needle grass where it is uneconomical or impractical to control, consideration should be given to utilisation in winter in combination with pasture topping or weed wiping in spring. In South America it is considered an important winter growing pasture grass. However, during summer it produces little green leaf and a large amount of unpalatable flower stalk.

Because of its lower palatability compared to other pasture species, a high density –short duration strategic grazing management system is preferable. This allows better utilisation of the pasture as well as allowing the faster growing desirable species such as fescue to slow the growth of Chilean needle grass through shading.

A heavy grazing with cattle in spring, when the flower heads were developing, reduces the number of flower stalks produced and made the grass more palatable to stock. Landholders have made Chilean needle grass dominated pastures more productive by using heavy stock densities for a short duration during the flowering period. Spraytopping of the pasture in the early flowering period with very low herbicide rates is also said to increase palatability.

The most important thing in any system of grazing management is to maintain good ground cover and favourable conditions for the faster growing desirable pasture species.

Chemical control

In research conducted by NSW DPI glyphosate gave 90% control at 1.5 L/ha when applied in autumn, but was significantly less effective from a spring application. By contrast fluproponate was equally effective from a spring or autumn application.

Chemical control is a useful tool to be used in a management program. Herbicide application before direct drilling is essential. Later in a program, spot spraying of re-invading seedlings will also be vital to reduce pasture degradation.

Glyphosate will generally be preferred to fluproponate for initial boom spraying in autumn where the area is to be resown because of the high cost of fluproponate. Glyphosate is used for or to assist in seedbed preparation prior to direct drilling, conventional preparation or aerial seeding.

Fluproponate would be preferred for smaller infestations, spot spraying or removing Chilean needle grass from an established pasture where the infestation is large enough to warrant boom spraying. At registered boom spraying rates fluproponate has reasonable selectivity, leaving behind pasture species such as fescue and cocksfoot.

However some pasture species are sensitive to fluproponate depending on timing — for example phalaris is sensitive to autumn applications but has little effect when applied in summer. Label information on selectivity should be carefully read. Manufacturers should be contacted if in doubt.

Under some circumstances, usually at flowering, low rates of glyphosate can be added to the slower acting fluproponate to provide a quicker desiccation and reduce seed production. 

Weed wipers using glyphosate have been used on Chilean needle grass with varying success. If plants are wiped between flowering and milky-dough stage (usually November to early December) panicle seed set is prevented. This overcomes seed problems when grazing (wool vegetable fault and eye/carcass injuries). Wiping to kill plants has not been highly successful, with less than 60% kill.

Pasture topping is a useful technique for seed sterilisation in spring/early summer. For sheep producers this allows Chilean needle grass paddocks to be grazed (after complying with chemical withholding periods) without the panicle seed causing significant problems with wool vegetable fault or eye/carcass injuries. It also significantly reduces the amount of seed going to the soil seed bank.

Chemical control has its drawbacks. The non-selectivity of most herbicides result in the death of both desirable and target species. Since Chilean needle grass has a large seed bank and a requirement for bare ground to establish, the resulting vegetation after herbicide application may actually have a greater proportion of the weed. Bare ground resulting from herbicide application should be re-seeded to provide the germinating Chilean needle grass with competition. If there are only a few plants it is probably better to remove them by hand than create a bare area with spot spraying.

It must be emphasised that chemical application alone will not control Chilean needle grass.

Herbicide options

WARNING - ALWAYS READ THE LABEL
Users of agricultural or veterinary chemical products must always read the label and any permit, before using the product, and strictly comply with the directions on the label and the conditions of any permit. Users are not absolved from compliance with the directions on the label or the conditions of the permit by reason of any statement made or not made in this information. To view permits or product labels go to the Australian Pesticides and Veterinary Medicines Authority website www.apvma.gov.au

See Using herbicides for more information.


PERMIT 9792 Expires 30/11/2020
Glyphosate 360 g/L (Roundup®)
Rate: 1 L per 100 L water
Comments: Spot spray
Withholding period: Nil.
Herbicide group: M, Inhibitors of EPSP synthase
Resistance risk: Moderate


PERMIT 9792 Expires 30/11/2020
Glyphosate 360 g/L (Roundup®)
Rate: 1 L/ha
Comments: Boom spray
Withholding period: Nil.
Herbicide group: M, Inhibitors of EPSP synthase
Resistance risk: Moderate


Flupropanate 745 g/L (Tussock®)
Rate: 1.5–3.0 L/ha
Comments: Boom application. Apply to actively growing plants.
Withholding period: Don't graze cows or goats that are being milked on treated areas. Blanket sprayed pastures - grazing or cutting for stock feed - 120 days. Spot sprayed areas - grazing or cutting for stock feed - 14 days. Don't graze stock on treated areas for 14 days prior to slaughter.
Herbicide group: J, Inhibitors of fat synthesis (Not ACCase inhibitors)
Resistance risk: Moderate


Flupropanate 745 g/L with Glyphosate 360 g/L (Various products)
Rate: 200 mL flupropanate plus 150 mL glyphosate 360g/L per 100 L of water
Comments: Spot spray application. Apply to actively growing plants.
Withholding period: Don't graze cows or goats that are being milked on treated areas. Blanket sprayed pastures - grazing or cutting for stock feed - 120 days. Spot sprayed areas - grazing or cutting for stock feed - 14 days. Don't graze stock on treated areas for 14 days prior to slaughter.
Herbicide group: J, Inhibitors of fat synthesis (Not ACCase inhibitors)
Resistance risk: Moderate


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Biosecurity duty

The content provided here is for information purposes only and is taken from the Biosecurity Act 2015 and its subordinate legislation, and the Regional Strategic Weed Management Plans (published by each Local Land Services region in NSW). It describes the state and regional priorities for weeds in New South Wales, Australia.

Area Duty
All of NSW General Biosecurity Duty
All plants are regulated with a general biosecurity duty to prevent, eliminate or minimise any biosecurity risk they may pose. Any person who deals with any plant, who knows (or ought to know) of any biosecurity risk, has a duty to ensure the risk is prevented, eliminated or minimised, so far as is reasonably practicable.
All of NSW Mandatory Measure
Must not be imported into the State or sold
Central Tablelands
Exclusion zone: whole region except for the core infestation area of Bathurst Council, Blayney Council, Lithgow Council, Oberon Council, Cabonne Council and Cowra Council
Regional Recommended Measure*
Exclusion zone: The plant should be eradicated from the land and the land kept free of the plant. Land managers should mitigate the risk of the plant being introduced to their land. Core infestation area: Land managers should mitigate spread from their land.
Central West Regional Recommended Measure*
Land managers should mitigate the risk of new weeds being introduced to their land. The plant should be eradicated from the land and the land kept free of the plant. The plant should not be bought, sold, grown, carried or released into the environment. Notify local control authority if found.
Hunter Regional Recommended Measure*
Land managers should mitigate the risk of new weeds being introduced to their land. The plant should be eradicated from the land and the land kept free of the plant. The plant should not be bought, sold, grown, carried or released into the environment. Notify local control authority if found.
Murray Regional Recommended Measure*
Land managers should mitigate the risk of new weeds being introduced to their land. Land managers should mitigate spread from their land. Notify local control authority if found.
North West
An exclusion zone is established for all lands in the region, except the core infestation area comprising the Tamworth Regional council
Regional Recommended Measure*
Whole of region: The plant should not be bought, sold, grown, carried or released into the environment. Exclusion zone: Land managers should mitigate the risk of new weeds being introduced to their land; land managers should mitigate spread from their land. Core infestation: Land managers reduce impacts from the plant on priority assets
Northern Tablelands Regional Recommended Measure*
Land managers should mitigate the risk of new weeds being introduced to their land. Land managers should mitigate spread from their land. The plant should not be bought, sold, grown, carried or released into the environment.
Riverina Regional Recommended Measure*
Land managers should mitigate the risk of new weeds being introduced to their land. The plant should be eradicated from the land and the land kept free of the plant. Notify local control authority if found.
South East
Exclusion zone: whole of region except core infestation area of Wollongong, Kiama, Shellharbour, Wingecarribee, Gouburn/Murwaree, and Queanbeyan/Palerang
Regional Recommended Measure*
Whole region: Land managers should mitigate the risk of new weeds being introduced to their land. Exclusion zone: The plant should be eradicated from the land and the land kept free of the plant.
*To see the Regional Strategic Weeds Management Plans containing demonstrated outcomes that fulfill the general biosecurity duty for this weed click here

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For technical advice and assistance with identification please contact your local council weeds officer.
For further information call the NSW Invasive Plants and Animals Enquiry Line on 1800 680 244 or send an email to weeds@dpi.nsw.gov.au

Reviewed 2017