The project helps control serrated tussock by providing advice, education and financial assistance to affected landowners. Since its inception in 2001, it has been responsible for implementing control work on approximately 2,000 hectares of infested land, and involving 150 landowners.
The project ensures long-term control by training up landowners and managers with the necessary skills to identify and control the weed. As well, initial control works are only performed if there is a three-year agreement with the landowner to provide ongoing control over that period.
The project is currently inactive awaiting refunding.
For more information, contact Tasmanian Land & Water Professionals on 03 6234 2939, or email admint[at]tlwp.com.au.
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Tasmanian Serrated Tussock Handbook (PDF 1.3MB)
Serrated Tussock Notes (PDF 355KB)
Why is it a weed?
Serrated tussock is one of the worst weeds in Australia. It is an aggressive, invasive perennial grass with the ability to survive under dry conditions.
It is a weed of grazing lands with poor soil fertility and low rainfall. In these areas, competing vegetation is limited and the benefits of control are marginal.
Serrated tussock is unpalatable and rarely eaten by stock. It has no nutritional value (17-25% digestibility, 4% protein and 86 % fibre) and stock given only access to serrated tussock will quickly loose condition. Worse still, due to its very low digestibility, stock forced to eat serrated tussock will starve to death despite having a full stomach.
Dense infestations can completely dominate pasture, making it incapable of supporting livestock. It is also a serious environmental weed that invades dry coastal vegetation, grasslands and open woodlands.
Serrated tussock is a proclaimed noxious weed in Tasmania and a Weed of National Significance.
Where did it come from?
Serrated tussock is a native of the pampas grasslands of South America. It is thought to have been introduced to Tasmania via contaminated pea seed imported from New Zealand in the 1920s. The first infestation was found at Sandford in 1956 and by 1965 there were 3200ha of affected land in the State.
Where is it found?
Currently, there are an estimated 2,000 hectares of affected land in Tasmania, restricted to the Clarence, Sorell, Tasman and King Island municipalities. Though recently, a new infestation has been found near Swansea on the East Coast.
There is a very real risk that serrated tussock will become established in the pastoral midlands where conditions would suit it admirably. Once there, it would be extremely difficult to control and would render large areas of land unusable.
Australia-wide, serrated tussock infests more than one million hectares, with the possibility of increasing to 30 million hectares if left unmanaged. It is also a serious weed in New Zealand and South Africa with small infestations occurring in England, France, Italy, Scotland and the United States.
How does it spread?
Serrated tussock is mainly spread by wind-borne seed. Mature plants can produce more than 140,000 seeds per plant per year, and the very light seeds can be blown up to 20km.
Seeds can also be spread by humans and animals. They can attach to fleeces or lodge in mud on the hooves of livestock. They can attach to cultivating and slashing implements, to tyres and even to firewood.
Buried seeds can remain viable for up to 15 years, so reducing soil disturbance is a good management practice. Serrated tussock seedlings are usually out competed by other plants, but can quickly become established when other vegetation is removed, such as through overgrazing or drought conditions.
What does it look like?
Serrated tussock is a perennial, tussock forming grass with a deep, fibrous root system, similar in general appearance to several of our native tussocks.
Leaves:
Young plants are erect and densely tufted with tightly inrolled leaves; the leaves are bright green and the leaf sheaths at the base are pale, more slender and closely packed than in the native tussocks. As the plant grows to maturity, the later leaves become longer, the tips turning to brownish green or, in winter, a bleached straw colour. Leaves at all growth stages feel rough or serrated if the finger and thumb are drawn down the blade. By the time the tussock is at the flowering stage the leaves are long and drooping.
Flowers:
Flower stalks usually appear in spring, earlier in dry years and later in years when an adequate water supply allows a longer period of vegetative growth. The flowering heads are carried on slender stalks slightly longer than the leaves. The flower head is an open, branched panicle, the primary branches in pairs, each pair distant from the next, slender and drooping. Each floret, purple in colour, produces one seed, about 2 mm long, pale straw coloured, with a tuft of short hairs at the base and a long, slender, twisted awn from the tip. A tussock in full flower presents a distinctly purple appearance due to the large number of purple florets.
Seeds:
When the seeds are ripe the stalk becomes very brittle, the first strong wind breaks it off and the whole seed head is blown along until it lodges against some obstacle. As the seed head dries out, the seeds are released and fall to the ground to begin a new colony. It has been estimated that a hectare of dense tussock can produce over 2 tonnes of seed or about 500 million seeds.
Serrated tussock resembles many native grasses, including Poa labillardieri, Poa poiformis, Stipa spp, Danthonia pallida and Deyeuxia nudiflora. The following characteristics enable serrated tussock to be distinguished from other tussocks throughout the year:
- Leaf bases of serrated tussock are more tightly packed and more slender than those of other tussocks and are never purple or blue-green, but a whitish colour.
- In autumn when most other grasses have dried off to a straw-colour, the young serrated tussock plants still retain their bright green colour, except for the tips, which are bleached.
- At the junction of leaf sheath and blade most grasses carry a small flap known as a 'ligule'. In the case of serrated tussock this is white, papery, rounded at the tip and never hairy.
- The upward-pointing barbs on the leaf blade, which gives them their rough or serrated texture, are minute and almost invisible to the naked eye. If the leaves appear at all hairy, the plant is not serrated tussock.
- The seed head breaks off whole. If the previous year's seed heads remain on the plant, it is not serrated tussock.
- Serrated tussock is rarely found in swampy or heavily timbered areas.
- Flowering and seedling heads are a dark purple due to the colour of the two 'glumes' surrounding the seed.
- Seed of serrated tussock is unlike the seed of any of the other tussock grasses with which it is likely to be confused.
How can it be controlled?
For long-term control, vigorous improved pastures must be established to compete with serrated tussock to help prevent re-invasion. Ploughing or spraying alone without pasture establishment is not effective because serrated tussock will regenerate from seed reserves in the soil.
All control programs should aim at reducing the amount of serrated tussock available to germinate on your property. Hilltops should be a priority for control works as they are an important source of wind borne seed spread to surrounding areas.
The principles and methods of serrated tussock control are:
- Prevention
- Chipping or spot spraying individual plants and small patches
- Cultivation or boom spraying large infestations
- Replacing dead tussock with improved perennial pasture
- Management to maintain a competitive perennial pasture
- Alternative measures
- Continual follow up
Click here for options for control in native grasslands.
a) Prevention
- Preventing the invasion of serrated tussock is the cheapest and most effective way of controlling it.
- Learn to identify serrated tussock, regularly check for it and act immediately to remove it.
- Place stock grazed on serrated tussock in a holding paddock to empty them out of faeces containing seed, before moving into a clean paddock.
Buy certified seed and avoid purchasing hay or stock from contaminated areas. - Establish tree belts or phalaris barriers along boundaries with infested properties to help reduce the amount of seed blowing into your property.
- Keep pastures vigorous and manage grazing so that no bare patches develop.
b) Chipping and Spot Spraying
Do not let serrated tussock establish beyond a scattered low density or else control measures become expensive and difficult. This means that each year every paddock must be searched for serrated tussock. Spot spraying and chipping is used to remove isolated or small patches of plants.
The most common herbicide used for control of serrated tussock is Flupropanate (Trade names Kenock, Tussock, Taskforce, Smack, Senock, Rambo). Spray to completely wet the plant and cause runoff. Add a dye to the spray mixture to identify areas sprayed. Apply Flupropanate at 2mL per 1L of water. To stop the plant from producing seed, spray before the end of July, as Flupropanate is slow acting and can take 12 to 18 months to kill serrated tussock. Flupropanate will kill seeds that germinate soon after spraying. Always follow label instructions and note withholding periods when using Flupropanate. Click here for more critical comments on the use of Flupropanate.
Chip isolated plants with a mattock preferably before the tussocks set seed. In wet conditions, remove soil from the roots. Do not chip out large patches of serrated tussock where a seed bank has built up because any soil disturbance will cause the germination of seeds.
The optimum time to kill serrated tussock is when it is found. Therefore be prepared e.g. keep a mattock in the back of your ute. Once serrated tussock has been removed, it is important to replace it with improved pasture. If the area is left bare, tussock will re-invade the site.
c) Removing large infestations
Cultivation: Serrated tussock can be successfully controlled using a program of cultivation, cropping and pasture improvement. Cultivation and cropping acts to reduce the seed reserves of serrated tussock available to germinate. Serrated tussock seedlings cannot emerge from being buried below 2 cm. Research has found chisel ploughing is not effective but mouldboard ploughing and disc ploughing are successful in burying the seed.
Paddocks that cannot be cultivated have the disadvantage of not reducing the seed bank of serrated tussock before sowing pasture. Therefore every effort should be made to cultivate and crop.
This program involves burning in winter and ploughing soon after to a depth of 10 cm. The paddock is left fallow and cultivated again in summer to remove any new tussocks. Cropping occurs for two years before sowing pasture to further reduce the reserve of tussock seed in the soil. Advice should be sought on the suitability of these cultivating techniques on specific areas of land in terms of soil erosion risk.
Boom or aerial spraying:
Serrated tussock can be boom or aerial sprayed with Flupropanate. Flupropanate will kill annual grasses and some native grasses, making re-seeding necessary. Apply Flupropanate at 2 L/ha between October and February, when there is adequate ground moisture to transport the chemical into the root zone where it is taken up by the plant. Flupropanate will not work under drought conditions. When applying Flupropanate by air use a water rate of 40L/ha to 80 L/ha or by ground spraying 150L/ha. Click here for more critical comments on the use of Flupropanate.
d) Replacing dead tussock with improved pasture
After cultivation or spraying, an improved perennial pasture must be planted back to provide long-term control of serrated tussock. Serrated tussock seedlings which germinate are weak and slow to establish and therefore can be out competed with vigorous grasses.
Important: Before sowing improved pasture species, 100 mm of rainfall must fall to leach Flupropanate out of the soil profile.
Improved introduced pasture species respond better to fertiliser than serrated tussock, therefore soil testing and adequate fertiliser use is important with pasture management for serrated tussock.
Pasture species: Phalaris and cocksfoot are two of the most useful grass species to compete against serrated tussock. Both perennial grasses are deep rooted, drought tolerant and therefore more persistent than perennial ryegrass in areas with dry summers. Phalaris is suited to heavy clay soils and is a larger plant than cocksfoot and therefore better able to compete with serrated tussock. However, cocksfoot can tolerate a lighter and less fertile soil than phalaris.
Also sow a mixture of subclover cultivars. Encourage the pasture to become dominant with clover in the first year, which will smother out any new tussock seedlings and make nitrogen available to the improved grasses. The nitrogen will help the pasture to become grass dominant which will provide long-term control of serrated tussock.
Grazing Management: Avoid grazing new pasture until pasture grasses and clovers have set seed. This allows young plants to fully develop and produce seed, which thickens up the pasture in the following year. Aerial sown pastures are slower to establish than those conventionally sown and need to be spelled into late summer. In late summer, graze down surplus pasture to promote autumn regrowth and clover germination. Spell the new pasture for a month after the autumn break to encourage clover germination.
Serrated tussock can germinate in response to rainfall in any season. It is critical to keep good pasture cover at all times to restrict the establishment of serrated tussock. In the second and third years of a new pasture, spell over spring and summer to smother out the many serrated tussock seedlings that will germinate. Generally, feed is in surplus so that the pasture can be spelled at this time.
e) Maintaining vigorous pastures
To maintain a vigorous perennial pasture, fertiliser will need to be applied annually in autumn. Phosphorus (P) is generally a limiting nutrient and at least 11 kg P/ha: (equivalent to 125 kg/ha of superphosphate) needs to be applied each year.
Avoid overgrazing, as this will encourage reinvasion of serrated tussock. Pasture should contain at least 80% groundcover at all times. If the pasture becomes invaded with weeds other than serrated tussock, herbicide manipulation and/or rotational grazing could help to remove annual grasses or broadleaf weeds.
f) Alternative measures
Burning: In areas of low rainfall and soil fertility where improved pasture is too risky to sow and the serrated tussock density is high, burning each year can help in control.
Burning will not kill serrated tussock, but burning in winter will stop the majority of plants from setting seed and therefore spreading. It will also reduce the fire hazard over the summer period.
Burning initially opens up the pasture. However, by leaving bare areas it also allows serrated tussock to further invade and for this reason should only be done where serrated tussock is at a high density.
Please consult your local Fire Authority captain before burning.
Goats: Goats will graze serrated tussock and can effectively control it, if serrated tussock occupies less than 20% of the pasture. Cattle and sheep are not effective in controlling serrated tussock.
Trees: Dense tree plantings that provide good shade can kill serrated tussock. Commercial pine plantations are used in serrated tussock control in NSW. Windbreaks also play a role in trapping serrated tussock seed and preventing them from blowing any further.
g) Continual follow-up
Serrated tussock will re-invade an improved pasture, particularly if it is weakened or by the sheer amount of seed in the soil. However, re-invasion will be much smaller and slower than in an unimproved pasture.
Once tussocks re-invade an improved pasture they can be removed by spot spraying or chipping, Aim not to let serrated tussock set seed. If the reinvasion is large then serrated tussock can be selectively removed from an improved pasture by using a blanket application of Flupropanate. Flupropanate applied at 2 L/ha in summer, when improved grasses are dormant or not actively growing, should not kill these pasture species, although some damage will occur. Phalaris is the most tolerant grass species to Flupropanate. Grazing down the improved pasture species before spraying at the correct rate will minimise pasture damage.
Once you start on a control program, make sure you complete it and do not give up! Serrated tussock can be controlled but you have to work at it.
Additional comments for the use of Flupropanate.
Graze first to reduce cover of desirable species before spraying. This will help to limit damage to pasture species and increase contact of serrated tussock with the herbicide.
Spot spraying – spray to run off at any time from Spring through to Autumn.
Aerial application to pastures should be in 40 – 80 L of water per hectare. For ground application, use 150 L/ha. For spot spraying, use 1000 L/ha or for a 15 L knapsack treat 150 square metres.
The optimum timing of application to avoid damage to desirable pasture species and/or to allow Flupropanate residues to be leached from the soil prior to Autumn reseeding is the period November to February inclusive. Precautions on reseeding and protection of pasture legumes must be observed.
Flupropanate is very slow acting and control of existing growth will take 3-12 months depending upon weather conditions and plant senescence.
Control under shade may be reduced.
Subterranean clover and other annual legumes may be damaged by Flupropanate if exposed to this spray or if they germinate before product residues have dissipated from the soil. Do not treat pastures with the product more than once a year.
Addition of wetter (e.g. 60 mL of Kenwet per 100 L of spray solution) is recommended.
2,2 DPA may be added to Flupropanate in order to obtain a quicker kill. No herbicides should be applied with Flupropanate if desirable pasture species are to be kept. For more rapid knockdown of existing annual weeds, diquat may be added.
Desirable species such as phalaris, cocksfoot, ryegrass, red and white clovers, subterranean clovers and Lucerne may be sown once at least 100 mm of leaching rain as fallen. If drought conditions prevail defer sowing until next season.
Options for Control in Native Grassland
Serrated tussock is a difficult weed to manage in native grasslands. There is some evidence that native grasses, in particular, the summer growing grasses Themeda triandra and Bothriochloa macra may prevent invasion of serrated tussock or limit its spread. The native grasses must be more than 50% of the sward to be effective, and grazing must be removed for a positive result. Fertiliser assists the process but only if grazing is removed.
Some success has been achieved using the spray and hay technique to rehabilitate native pastures. This technique involves removing serrated tussock with herbicide, covering with Themeda seed and mulch, and burning or otherwise removing the mulch layer in springtime. Success using this method depends on seed quality and quantity, method to introduce seed to the soil, timing of weed control, timing of seed broadcasting and timing of removal of thatch.
Herbicides may be used in native pastures. Kenock is reported to kill serrated tussock, being selective on the natives Themeda triandra, Bothriochloa macra and Poa labillardieri. Kenock, however, kills Danthonia spp. and Microlaena stipoides.
Burning should also be used in the management of native pastures, reducing fire risk, preventing or minimizing seeding and increases the effectiveness of subsequent herbicide applications.
