Serrated tussock (Nassella trichotoma)

Serrated tussock is a drought tolerant grass with low feed value. It takes over pastures and native vegetation.

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How does this weed affect you?

Serrated tussock is not palatable to livestock and has little feed value. Animals forced to graze serrated tussock can become malnourished and may die with a stomach full of partly digested serrated tussock. Serrated tussock can:

• take over pastures and native vegetation
• reduce pasture quality
• contaminate hay and grain.

The native vegetation communities at risk include:

• native grasslands
• grassy woodlands
• dry forests
• some coastal vegetation.

Serrated tussock can completely take over new areas within 4 years. It is similar in appearance to many native species making it difficult to identify when not in flower. Subsequently, it can go unnoticed for many years. A single plant can produce up to 140,000 seeds each season. Serrated tussock is hard to get rid of, control is costly and herbicides used to control serrated tussock impact other grasses, especially natives.

What does it look like?

Serrated tussock grows in upright tussocks up to 45 cm tall and 25 cm wide.

The colour of the plant changes over seasons. In:

• spring, the clumps are light green with brown tips on the leaves
• late spring and early summer, the clumps have a purple tinge when the seed heads are fully emerged
• summer, plants are green when other grasses turn brown
• winter when frosted, the plants turn a golden yellow.

Leaves are:

• very narrow and tightly rolled
• upright and stiff
• whitish at the base, looking like shallots
• serrated, felt when drawing the leaf between your fingers.

Ligule:

The ligule is one of the key identification features for serrated tussock. The ligule can be found at the junction of the leaf sheath and the leaf. Slowly separate and bend the leaf back to see if there is a small, milky coloured, hairless flap 1mm long protruding vertically

Seedheads:

Multiple seedheads are produced and can be present from September to March . Each seedhead:

• has multiple branches with a single seed at the end of each branch
• is up to 35 cm long and they tend to “weep” over the plant
• can break off when mature and be easily blow away by the wind
• has a purple tinge when mature due to the reddish brown or purple bracts wrapping around each seed.

Seeds:

• are golden brown and hard
• are small, 1.5 mm long
• have a ring of white hairs where they connect to the plant
• have an awn 25 mm long, offset from the centre at the other end of the seed.

Roots are:

• deep
• fibrous
• difficult to pull out of the ground, even when plants are small.

Similar looking plants

Serrated tussock looks like some native Australian grasses including:

• corkscrew grass (Austrostipa setacea)
• poa tussock (Poa labillardierei)
• snowgrass (Poa sieberiana)
• wallaby grass (Rytidosperma pallidum).

Key features of serrated tussock are:

• leaves are rolled rather than folded
• leaf base is white
• ligule is 1 mm long, white and hairless.

Where is it found?

The main infestations are in the Central and Southern Tablelands of NSW. There is some serrated tussock on the Northern Tablelands.

It was first introduced to Australia in the early 1900s and first identified in 1935. In 1976, 680 000 ha of NSW had serrated tussock. By 2003 this area had increased to 820 000 ha. The area with serrated tussock within NSW continues to increase.

Serrated tussock is native to South America. It is a weed in New Zealand, South Africa, Europe and North America.

What type of environment does it grow in?

Serrated tussock prefers to grow on the tablelands of NSW, although it can be found on the coast and slopes. The optimum temperature range is 10 - 15 °C. It tolerates:

• acid and alkaline soil 
• dry conditions
• rocky areas
• shallow soil if it is not in competition with other plants
• soils derived from basalt, granite, shale, slate and sandstone.

It does not grow well in:

• hot weather
• wet areas
• heavy shade e.g. under a thick tree canopy
• saline soils or salty areas
• competition from other plants.

Maps and records

• Recorded presence of Serrated tussock during property inspections (Map: Biosecurity Information System - Weeds, 2017-2023)
  These records are made by authorised officers during property inspections under the Biosecurity Act 2015. Officers record the presence of priority weeds in their council area and provide this to the NSW Department of Primary Industries. Records reflect the presence of the weed on the date of inspection.
  
  

How does it spread?

Serrated tussock seeds can spread long distances by wind and water. Wind is the main way it is spread. The mature seed heads break of at the base and are carried long distances by wind - 10 km or more if conditions are favourable. Seeds have been known to move 60 km downstream from the nearest infestation on the banks of the Macquarie River.

Seeds also spread with feed, animals and machinery.  Animals can pick up seeds in hooves, fleeces or coats. Serrated tussock seeds remain viable passing through an animal’s gut.

Serrated tussock colonises bare areas. Drought causing bare ground favours serrated tussock. Sandy, nutrient poor soils are at most risk.

References

Ayres, L. and Leech, F. (2006). Serrated tussock – identification and control, Primefact 44. NSW DPI, Orange.

Auld BA and Coote BG (1981). Prediction of pasture invasion by Nassella trichotoma(Gramineae) in South East Australia. Protection ecology 3, 271-277.

Badgery, W.B., Kemp, D.R., Michalk. D.L. and King, W.M. (2005). Competition for nitrogen between Australian native grasses and the introduced weed Nassella trichotoma. Annals of Botany 96, 799-809.

Badgery, W.B., Kemp, D.R., Michalk DL, King WM (2008). Studies of competition between Nassella trichotoma (Nees) Hack. ex Arechav. (serrated tussock) and native pastures. 1. Adult plants. Australian Journal of Agricultural Research 59, 226-236.

Badgery W.B., Kemp, D.R., Michalk, D.L. and King, W.M. (2008). Studies of competition between Nassella trichotoma (Nees) Hack. ex Arechav. (serrated tussock) and native pastures. 2. Seedling responses. Australian Journal of Agricultural Research 59, 237-246.

McLaren, D. and Grech, C. (2010). Primefact 1013 - Recognising, managing and preventing herbicide resistance in serrated tussock. Industry and Investment NSW.

Kidston, J., Ferguson, N., and Scott., M. (2010). Weed Control in Lucerne and Pastures 2010. Industry and Investment NSW.

Osmond, R., Verbeek, M., McLaren, D.A., Michelmore, M., Wicks, B., Grech, C.J. and Fullerton, P. (2008). Serrated tussock - National Best Practice Management Manual. Victorian Department of Primary Industries.

PlantNET (The NSW Plant Information Network System). Royal Botanic Gardens and Domain Trust, Sydney. Retrieved 2 February 2022 from: https://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Nassella~trichotoma

More information

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Control

Successful weed control relies on early action and follow up after initial efforts. Using a combination of control methods is usually more successful.

Prevention:

• Learn how to identify serrated tussock.
• Control plants quickly, delaying control allows a quick transition to more and more plants. Larger infestations become costly and difficult to control.
• Limit animal movement from infested areas into clean paddocks.
• Quarantine stock from infested areas for at least 10 days to pass seed through the gut before releasing them to clean paddocks.
• Avoid bringing hay, grain, or silage from serrated tussock areas onto your property.
• Inspect hay or fodder (even from clean areas) for weed seeds.
• Plant windbreaks to reduce seeds blowing in.
• Clean vehicles and machinery before moving into clean areas. 

Pasture management

Maintaining healthy pastures and 100% ground cover is the best long-term defence against serrated tussock. 

Establishing and maintaining healthy pastures can require different techniques and this will be influenced by many factors such as topography, rainfall, grazing management, and soil type. Further information is available on the Pastures and Rangelands section of NSW DPI website.

Grazing

Serrated tussock is not very palatable and has little feed value. Animals can graze it for short periods, but will lose condition. Animals favour other pasture species over serrated tussock. This promotes the dominance of the weed. Pastures will deteriorate with continuous grazing.

Physical removal

Remove individual plants with a mattock in small, isolated patches. Bag and dispose of the plants. Also dispose of soil attached to roots as it may contain seeds. Tussocks with flowers should be burnt after removal.

Sow pasture seed where the ground is bare.

Forestry

Planting trees with a dense canopy like pines is an effective long-term strategy. It will take many years for trees to be large enough to suppress serrated tussock. Use other control methods in the meantime. Commercial forestry may be an option. Seek expert advice before investing in forestry projects.

Biological control

There are no effective biological control agents in Australia for serrated tussock.

Chemical control

Most herbicides used to control serrated tussock contain either glyphosate or flupropanate. Pasture species have variable tolerance to these herbicides. Check which pasture species are present prior to determining which chemical control option can be used.   

Herbicides are most effective in combination with healthy, competitive pastures. Repeated use of the same herbicide can lead to herbicide resistance.

Always observe grazing withholding periods following herbicide treatments in pastures.

Flupropanate herbicides

Legumes and some native pasture species (e.g. weeping grass, wallaby grass, spear grass) can be killed by flupropanate herbicides. Kangaroo grass and redgrass are more tolerant.

Flupropanate can remain active in the soil for up to two years. Residual activity depends on the amount of rainfall. Residual activity is longer with low rainfall or drought. Flupropanate continues killing serrated tussock seedlings until 100mm of leaching rainfall has fallen.

The herbicide washes out faster from sandy soils than clay soils. Do not sow a new pasture or crop until flupropanate is likely to have washed out of the root zone.

Flupropanate takes several months to kill serrated tussock. It may not stop seed production when applied after mid-August. Apply 2 – 4 weeks before seed heads emerge (indicated by thickening of tillers). After seeding, use a mix of glyphosate + flupropanate.

Label rates of flupropanate control serrated tussock with minimal damage to young native trees.

Glyphosate herbicides

Use glyphosate for a complete knockdown of serrated tussock and other weeds. Glyphosate has no residual effect. Carefully timed applications can allow some selectivity - killing serrated tussock whilst preserving dormant desirable pastures. It is important to get good spray coverage of all the target plant or it may recover.  

Apply glyphosate:

• in spring before crop or pasture in autumn
• just before sowing in autumn
• when plants are actively growing
• to spot spray serrated tussock before it seeds.

Avoid using glyphosate when:

• soil is dry and serrated tussock plants are stressed
• there are frosts or dew on the plant
• dead plant material covers the growing parts of weeds.

Glyphosate can be unreliable when:

• tussocks are mature,
• AND growing on fertile clay soils,
• AND there is low rainfall.

Spot spraying

Spot spray individual clumps or small patches year round, before plants set seed. Calibrate spray equipment to ensure you apply the correct rate of herbicide. Only spray the tussock plants. A spray shield can minimise damage to surrounding plants. Check paddocks after spraying for any missed plants.

Broadacre spraying

Herbicide can be applied with boomsprays or aircraft for larger areas.

Weed wipers

Graze to reduce the height of desirable pasture species before using wipers. Both flupropanate and glyphosate are suitable.

Wiping is only effective on large tussocks. Repeat treatment as smaller tussocks mature. Use the wiper in two directions to improve efficacy.

Herbicide resistance

Herbicide resistant plants that spread by seed are harder to control. Serrated tussock is not reported as resistant to glyphosate. It has become resistant to flupropanate in some areas.

Herbicide resistance is more likely to develop when treating large areas with a lot of weeds. Avoid herbicide resistance developing by:

• rotating flupropanate with glyphosate herbicide
• spraying before seed set
• using other control methods with herbicide (cropping, pasture, chipping, forestry, grazing and fertiliser)
• reducing populations over time
• checking for weed survival after spraying
• treating survivors with a different herbicide.

Herbicide options

See Using herbicides for more information.

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PERMIT 9792 Expires 30/11/2025
Glyphosate 360 g/L (Various products)
Rate: 1 L per 2 L of water
Comments: Wick wiping application.
Withholding period: Nil.
Herbicide group: 9 (previously group M), Inhibition of 5-enolpyruvyl shikimate-3 phosphate synthase (EPSP inhibition)
Resistance risk: Moderate

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Flupropanate 745 g/L (Tussock®)
Rate: 1.5–2.0 L/ha
Comments: Boom and aerial application. June to August inclusive. Four-month withholding period for blanket application.
Withholding period: Spot spray: Do NOT graze or cut for stock feed for at least 14 days. Blanket spray: Do NOT graze, or cut for stock feed for at least 4 months. If stock are grazed in treated areas after required time has passed, remove stock from treated areas and do NOT slaughter or milk for human consumption until they have been on clean feed for at least 14 days.
Herbicide group: 15 (previously group J), Inhibition of very long chain fatty acid synthesis (VLCFA inhibitors)
Resistance risk: Moderate

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Flupropanate 745 g/L (Tussock®)
Rate: 100–200 mL per 100 L of water
Comments: Spot spray from September to May. Four month withholding period for blanket application.
Withholding period: Spot spray: Do NOT graze or cut for stock feed for at least 14 days. Blanket spray: Do NOT graze, or cut for stock feed for at least 4 months. If stock are grazed in treated areas after required time has passed, remove stock from treated areas and do NOT slaughter or milk for human consumption until they have been on clean feed for at least 14 days.
Herbicide group: 15 (previously group J), Inhibition of very long chain fatty acid synthesis (VLCFA inhibitors)
Resistance risk: Moderate

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Flupropanate 86.9 g/kg (GP Flupropanate)
Rate: 15kg per ha
Comments: Apply February to December inclusive. Four month withholding period for blanket application.
Withholding period: Do not graze or cut for stock feed areas which have received any treatment other than spot treatment for at least 4 months. Spot treatment: Do not graze or cut for stock feed for at least 14 days. If stock are grazed in treated areas after required time has passed, remove stock from treated areas and do NOT slaughter or milk for human consumption until they have been on clean feed for at least 14 days. This requirement applies permanently to treated areas.
Herbicide group: 15 (previously group J), Inhibition of very long chain fatty acid synthesis (VLCFA inhibitors)
Resistance risk: Moderate

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Flupropanate 86.9 g/kg (GP Flupropanate)
Rate: 1.5g/m2
Comments: Spot application apply all year round.
Withholding period: Do not graze or cut for stock feed areas which have received any treatment other than spot treatment for at least 4 months. Spot treatment: Do not graze or cut for stock feed for at least 14 days. If stock are grazed in treated areas after required time has passed, remove stock from treated areas and do NOT slaughter or milk for human consumption until they have been on clean feed for at least 14 days. This requirement applies permanently to treated areas.
Herbicide group: 15 (previously group J), Inhibition of very long chain fatty acid synthesis (VLCFA inhibitors)
Resistance risk: Moderate

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Glyphosate 360 g/L (Various products)
Rate: 0.7–1.3 L to 100 L of water
Comments: Spot spray application.
Withholding period: Nil.
Herbicide group: 9 (previously group M), Inhibition of 5-enolpyruvyl shikimate-3 phosphate synthase (EPSP inhibition)
Resistance risk: Moderate

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Glyphosate 360 g/L (Various products)
Rate: 4.0–6.0 L/ha
Comments: Boom spray. Apply to actively growing, stress-free plants.
Withholding period: Nil.
Herbicide group: 9 (previously group M), Inhibition of 5-enolpyruvyl shikimate-3 phosphate synthase (EPSP inhibition)
Resistance risk: Moderate

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Glyphosate 360 g/L (Various products)
Rate: 0.75–1.25 L/ha
Comments: Spray topping application. Apply to actively growing, stress-free plants.
Withholding period: Nil.
Herbicide group: 9 (previously group M), Inhibition of 5-enolpyruvyl shikimate-3 phosphate synthase (EPSP inhibition)
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 pest 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	Prohibition on certain dealings Must not be imported into the state, sold, bartered, exchanged or offered for sale.
Central Tablelands	Regional Recommended Measure* (for Regional Priority - Asset Protection) Land managers should mitigate the risk of the plant being introduced to their land. Land managers should mitigate spread of the plant from their land. A person should not buy, sell, move, carry or release the plant into the environment. Land managers should reduce the impact of the plant on assets of high economic, environmental and/or social value.
Central West An exclusion zone is established for the whole of region, except the core infestation area which defined as from the Central West Local Land Services Boundary North along Burrendong Way to Stuart Town. East along Mookerawa Road to Burrendong Dam. East along Oaky Creek bounded by the Central West Local Land Service boundary.	Regional Recommended Measure* (for Regional Priority - Containment) Whole of region: Land managers mitigate the risk of new weeds being introduced to their land. Within exclusion zone: Land managers should eradicate the plant from the land and keep the land free of the plant. A person should not deal with the plant, where dealings include but are not limited to buying, selling, growing, moving, carrying or releasing the plant. Notify local control authority if found. Within core infestation: Land managers should mitigate spread of the plant from their land. A person should not buy, sell, move, carry or release the plant into the environment. Land managers should reduce the impact of the plant on assets of high economic, environmental and/or social value.
Greater Sydney Wollondilly Shire Council and Camden Council areas are classified as the core infestation area. An exclusion zone is established for the rest of the region.	Regional Recommended Measure* (for Regional Priority - Containment) Whole of region: Land managers should mitigate the risk of the plant being introduced to their land. Within exclusion zone: Land managers should eradicate the plant from the land and keep the land free of the plant. A person should not deal with the plant, where dealings include but are not limited to buying, selling, growing, moving, carrying or releasing the plant. Notify local control authority if found. Within core infestation area: Land managers should mitigate spread of the plant from their land. A person should not buy, sell, move, carry or release the plant into the environment.
Hunter	Regional Recommended Measure* (for Regional Priority - Prevention) Land managers should mitigate the risk of the plant being introduced to their land. Land managers should eradicate the plant from the land and keep the land free of the plant. A person should not deal with the plant, where dealings include but are not limited to buying, selling, growing, moving, carrying or releasing the plant. Notify local control authority if found.
Murray Core infestation zone: Federation Council, Greater Hume Council, Snowy Valleys Council. Exclusion zone: Albury City Council, Berrigan Shire Council, Edward River Council, Murray River Council, Murrumbidgee Council.	Regional Recommended Measure* (for Regional Priority - Containment) Within exclusion zone: Land managers should mitigate the risk of the plant being introduced to their land. Land managers should eradicate the plant from the land and keep the land free of the plant. A person should not deal with the plant, where dealings include but are not limited to buying, selling, growing, moving, carrying or releasing the plant. Notify local control authority if found. Within core infestation area: Land managers should mitigate the risk of the plant being introduced to their land. Land managers should mitigate spread of the plant from their land. A person should not buy, sell, move, carry or release the plant into the environment. Land managers should reduce the impact of the plant on assets of high economic, environmental and/or social value.
North West	Regional Recommended Measure* (for Regional Priority - Eradication) Land managers should mitigate the risk of the plant being introduced to their land. Land managers should eradicate the plant from the land and keep the land free of the plant. A person should not deal with the plant, where dealings include but are not limited to buying, selling, growing, moving, carrying or releasing the plant. Notify local control authority if found.
Northern Tablelands An exclusion zone is established for all the lands in the region, except the core infestation area comprising lands within the: Armidale Regional Council, Uralla Shire Council, Glen Innes Severn Council in the Deepwater area.	Regional Recommended Measure* (for Regional Priority - Containment) Whole of region: Land managers mitigate the risk of new weeds being introduced to their land. Within exclusion zone: Land managers should eradicate the plant from the land and keep the land free of the plant. A person should not deal with the plant, where dealings include but are not limited to buying, selling, growing, moving, carrying or releasing the plant. Notify local control authority if found. Within core infestation: Land managers should mitigate spread of the plant from their land. A person should not buy, sell, move, carry or release the plant into the environment. Land managers should reduce the impact of the plant on assets of high economic, environmental and/or social value.
Riverina	Regional Recommended Measure* (for Regional Priority - Eradication) Land managers should mitigate the risk of the plant being introduced to their land. Land managers should eradicate the plant from the land and keep the land free of the plant. A person should not deal with the plant, where dealings include but are not limited to buying, selling, growing, moving, carrying or releasing the plant. Notify local control authority if found. Your local biosecurity weeds officer can help to identify, advise on control, and how to remove this weed.
	*To see the Regional Strategic Weeds Management Plans containing demonstrated outcomes that fulfil the general biosecurity duty for this weed click here

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Reviewed 2023