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 stock. Animals grazing on it become malnourished.

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 hard to get rid of. A single plant can produce up to 140,000 seeds each season. Control is costly and herbicides used to control serrated tussock impact other grasses, especially natives.

Poor feed quality

Serrated tussock has extremely low nutritional value. All animals forced to graze serrated tussock will lose condition. Sheep lose weight and eventually die, with the stomach full of partly digested tussock at death.

Stock grazing dense serrated tussock for short to medium periods need feed supplements to provide energy and protein.

What does it look like?

Serrated tussock grows in upright tussocks up to 45 cm tall and 25 cm wide. In spring the clumps are light green with brown tips to the leaves. In late spring and early summer the clumps have a purple tinge when the seed heads emerge fully. Plants remain green in summer when other grasses turn brown. After frost the clumps turn a golden yellow.

Leaves are:

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

Serrated tussock has a small, thin structure at the base of the leaf blade. This is a ligule, and can look like a small piece of tissue paper. The ligule is 1 mm long, smooth and milky coloured.

Flowers are:

• on a spike that leans over
• clustered in a group up to 35 cm long
• branched with single flowers on each branch
• wrapped in reddish-brown or purple bracts.

Seeds are:

• in a seed head on the flower spike
• golden brown
• hard
• small, 1.5 mm long
• with a ring of white hairs where they connect to the plant
• with an awn (looks like a bristle or thick hair) 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. Similar looking native grasses include corkscrew grass, poa tussock, snowgrass and wallaby grass. It could be serrated tussock if the:

• leaves are rolled rather than folded
• leaf base is white
• ligule (a small flap at the base of the leaf) is 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 degrees C. It tolerates:

• acid and alkaline soil (low and high pH)
• 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 like:

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

Distribution map

• NSW (image)

How does it spread?

Serrated tussock seeds can spread long distances by wind and water. Wind is the main mechanism of spread. The ripe 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.

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Control

Long term control of serrated tussock needs to consider that:

• flowering times can change depending on seasonal conditions
• seed heads take about 10 weeks to develop
• seeds develop early to mid summer
• seeds germinate year round, but most germinate in Autumn following rain
• most seeds germinate
• some seeds remain viable in the soil for over 3 years
• seeds buried deeper than 1.8 cm are unlikely to germinate
• plants produce seeds from around 18 months old
• 4000 seedlings can establish per square meter, leaving 15 plants per square meter after 3 years.

Prevention:

• Control plants as soon as they appear and before they set seed.
• 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.
• Revegetate unproductive areas with trees and shrubs to resist invasion.
• Minimise soil disturbance on sandy soils - ploughing can cause a flush of seedling growth.
• Plant windbreaks to reduce seeds blowing in.
• Clean vehicles and machinery before moving into clean areas.

Early detection

Learn to identify serrated tussock. Keep checking feedout areas, paddocks and windbreaks for serrated tussock plants and control them. Delaying control of odd plants or light or scattered plants allows a quick transition to more and more plants. These quickly become more difficult and costly to control.

Pasture management

Maintaining healthy pastures is the best long-term defence against serrated tussock. Serrated tussock is unlikely to establish in a good perennial pasture with legumes. Thin and bare patches in the pasture are at most risk of invasion.

Dense pastures with 100% groundcover can prevent seedling establishment. To maintain healthy pastures:

• grow combinations of winter and summer pastures
• rest pastures between grazing periods
• adjust grazing to:
  • keep the ground covered with good pasture plants
  • have higher cover during summer when serrated tussock sets seed
• reduce numbers of grazing animals before overgrazing occurs
• test soil to check fertility
• use fertiliser if needed.

Cropping before pasture establishment

Cropping with weed control in spring and autumn reduces the weed seed bank. Control weeds for at least one year before sowing pasture.

Suitable crops include oats, winter wheats and forage brassicas. Disc ploughs can break up tussock clods and encourage seed germination. Avoid discing on shallow soils or slopes to protect the soil.

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.

Graze in autumn to remove dead plant litter and promote subterranean clover. Don’t over graze. Redgrass (Bothriocloa macra) competes well with serrated tussock.

Avoid grazing new pastures unless conditions are very good. Then a quick, light graze with cattle in spring can encourage pasture growth.

Physical removal

Remove individual plants with a mattock in small, isolated patches. Bag and dispose of the pulled out 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.

Before planting trees:

• spray out the serrated tussock
• cultivate or rip the soil.

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. Follow up is essential for successful control.

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:

• tussock 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 30/11/2020
Glyphosate 360 g/L (Roundup®)
Rate: 1 L per 2 L of water
Comments: Wick wiping application.
Withholding period: Nil.
Herbicide group: M, Inhibitors of EPSP synthase
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: 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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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: 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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Glyphosate 360 g/L (Roundup®)
Rate: 0.7–1.3 L to 100 L of water
Comments: Spot spray application.
Withholding period: Nil.
Herbicide group: M, Inhibitors of EPSP synthase
Resistance risk: Moderate

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Glyphosate 360 g/L (Roundup®)
Rate: 4.0–6.0 L/ha
Comments: Boom spray. Apply to actively growing, stress-free plants.
Withholding period: Nil.
Herbicide group: M, Inhibitors of EPSP synthase
Resistance risk: Moderate

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Glyphosate 360 g/L (Roundup®)
Rate: 0.75–1.25 L/ha
Comments: Spray topping application. Apply to actively growing, stress-free plants.
Withholding period: Nil.
Herbicide group: M, Inhibitors of EPSP synthase
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	Prohibition on dealings Must not be imported into the State or sold
Central 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. Protect conservation areas, natural environments and primary production lands that are free of serrated tussock
Central West Exclusion zone: whole region except for the core infestation area that is bounded by the Central West Local Land Services boundary north along Burrendong Way to Stuart Town, east along Mookerawa Road to Burrendong Dam, and east along Oaky Creek, bounded by the Central West Local Land Services boundary	Regional Recommended Measure* Whole region: The plant should not be bought, sold, grown, carried or released into the environment. 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 reduce impacts from the plant on priority assets. Land managers should mitigate the risk of the plant being introduced to their land.
Greater Sydney Exclusion zone: whole region excluding the core infestation area of Wollondilly and Camden	Regional Recommended Measure* Whole region: Land managers should mitigate the risk of new weeds being introduced to their land. The plant or parts of the plant should not be traded, carried, grown or released into the environment. Notify the Local Control Authority if found. Exclusion zone: The plant should be eradicated from the land and the land kept free of the plant. Core infestation: Land managers should mitigate spread from their land.
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. 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.
North West An exclusion zone is established for all lands in the region, except the core infestation area comprising all Local Government Areas east of the Newell Highway	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; the plant should be eradicated from the land and the land kept free of the plant. 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. Notify local control authority if found.
Riverina	Regional Recommended Measure* Land managers should mitigate the risk of the plant being introduced to their land. The plant should be eradicated from the land and the land kept free of the plant.
South East Core infestation: whole region except the exclusion zone of Shoalhaven, Eurobodalla, Kiama, Wollongong, Bega Valley and Shellharbour councils	Regional Recommended Measure* Whole region: Land managers should mitigate the risk of new weeds being introduced to their land. The plant should not be bought, sold, grown, carried or released into the environment. Exclusion zone: Land managers should mitigate spread from their land. Core area: Land managers reduce impacts from the plant on priority assets.
	*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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Reviewed 2018