Serrated tussock - Weed of National Significance
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|Recognising, managing and preventing herbicide resistance in serrated tussock|
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|Serrated Tussock National Best Practice Manual|
|Serrated tussock - weed management guide|
- Declared in NSW under the Noxious Weeds Act 1993 (Current Status)
- Weed of National Significance (definition)
Further InformationSpecific on-farm advice is essential when attempting to control serrated tussock on non-arable land. Consult your local agronomist or council weeds officer.
This website was launched by the Serrated Tussock Working Party for NSW & ACT. It provides useful information on the identification, control and management of serrated tussock.
When using herbicides 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 publication.
Parts of the chemical use pattern quoted in this publication are approved under permits issued by the Australian Pesticides and Veterinary Medicines Authority (APVMA) and in force at the time the publication was prepared. Persons wishing to use a chemical in the manner approved under permit should obtain a copy of the relevant permit from the APVMA www.apvma.gov.au and must read all the details, conditions and limitations relevant to that permit, and must comply with the details, conditions and limitations before using that chemical.
Pasture improvement cautions
Pasture improvement may be associated with an increase in the incidence of certain livestock health disorders. Livestock and production losses from some disorders are possible. Management may need to be modified to minimise risk. Consult your veterinarian or adviser when planning pasture improvement.
The Native Vegetation Act 2003 restricts some pasture improvement practices where existing pasture contains native species. Inquire through your office of the Department of Natural Resources for further details.
Serrated tussock (Nassella trichotoma) - Identification and Control
Serrated tussock is a perennial, drought-resistant, highly invasive tussock-forming grass which is a serious weed in Australia, New Zealand and South Africa. It is highly adapted to a range of environments, seeds prolifically and is difficult and costly to control. Large volumes of seed are spread long distances by wind; allowing new populations to establish over large areas.
Impact on agriculture
Serrated tussock can infest agricultural land ranging from highly arable and fertile areas through to steep and non-arable areas with low fertility. It will colonise both native and introduced pastures, and its spread is most rapid in degraded or disturbed pastures. It can be particularly difficult to control in native pastures as many native species are susceptible to flupropanate - the most commonly used selective herbicide for serrated tussock control. Uncontrolled serrated tussock can develop into a monoculture within a few of years.
Serrated tussock is not palatable for livestock and has little feed value. Significant infestations will dramatically reduce carrying capacities. A well managed pasture can carry around 7–15 dse/ha while heavy infestations of serrated tussock will reduce carrying capacities to as little as 0.5 dse/ha, and moderate infestations can reduce carrying capacity by approximately 40%. It is suggested that serrated tussock decreases carrying capacity proportionally to the level of infestation i.e. a 50% infestation level of serrated tussock reduces carrying capacity by 50%.
Serrated tussock seeds are also a serious contaminant of hay and grain. Farm machinery such as slashers, vehicles and tractors can readily transport seed to clean areas.
Control of serrated tussock within a farming system is on-going and often at great cost to producers, with production from infested country substantially reduced and land values lowered.
Impact in native ecosystems
Serrated tussock threatens the biodiversity of many native vegetation communities, including native grasslands, grassy woodlands, sclerophyll forests and some coastal vegetation.
Serrated tussock is very similar in appearance to many Australian native grass species making it hard to identify when not in flower. It can therefore go unnoticed for many years and eventually form monocultures in once diverse ecosystems. This reduction of biodiversity is a serious threat to native fauna and flora that inhabit these areas.
Origin and distribution
Serrated tussock is native to the South American countries of Peru, Chile, Uruguay and Argentina. It occurs as a weed in New Zealand and South Africa while small infestations also occur in England, France, Italy, Scotland and the USA.
Serrated tussock was first introduced to Australia as early as 1900 and was first identified in New South Wales (NSW) in 1935 from plants collected near the Yass River. It was promptly named ‘Yass River tussock’ or ‘Yass tussock’, and later re-named as ‘serrated tussock’, presumably because of its serrated leaves. In New Zealand it is known as ‘Nassella tussock’ named after the genus of the species.
In 1937 it was described as a potential weed in NSW, and in 1938 it was proclaimed noxious in many shires in the Central and Southern Tablelands and Monaro regions of NSW. It has now been declared noxious in many parts of NSW, Victoria and Tasmania and is a Weed of National Significance (WoNS).
Surveys conducted in 2003 indicate that the total area infested in NSW has increased to 820 000 ha (from 680 000 ha in 1976). A similar area again is threatened by further spread. In NSW the main infestations are in the Central and Southern Tablelands stretching from Mudgee south to the Victorian border and small areas on the Northern Tablelands.
It has not been discovered in Queensland, Western Australia or the Northern Territory.
Serrated tussock is best adapted to the tablelands of NSW, although some infestations occur on the coast and slopes. Plants require relatively cool conditions for growth and survival; the optimum temperature range is 10oC to 15oC. Hot summers have tended to restrict spread westward and to the north; however, some outbreaks have occurred in these areas. The plant is also capable of surviving severe droughts.
Serrated tussock can be found growing on soils derived from granite, basalt, shale, slate or sandstone. While adapted to nutrient-deficient soils it also responds to higher soil fertility. It is highly tolerant of acidic soils, and will also grow on basalt soils with higher pH. It is not often found in wet swampy areas, heavily shaded areas or areas affected by salinity, but is well adapted to rocky terrains. In the absence of competition from other vegetation, serrated tussock establishment is not restricted by shallow soils.
Correct identification of serrated tussock is essential in order to prevent spread. Several key features can be used to distinguish it from similar tussock forming grasses.
Mature tussocks can vary in size depending on soil fertility. In fertile soil, tussocks can grow to 45 cm in height and have a diameter at the base of 25 cm. In infertile soil or lighter soil types tussocks may be smaller.
Serrated tussock changes colour throughout the year. It is most recognisable when in full flower in late spring/summer when it has a distinct purple tinge.
After flowering in late summer, when seed heads are fully developed they are golden brown above a light green tussock base.
In late autumn and winter, frosting bleaches the tussocks a golden yellow. In early to mid spring the tussocks are light green with brown tips.
When recovering from burning or slashing, the tussocks have a light green appearance.
Serrated tussock leaves are tightly rolled, narrow, stiff and upright. They have small serrations that can be felt when the leaf is drawn between the fingers. Although the common name ‘serrated tussock’ suggests that these serrations are a key feature of the weed, reliance on serrations alone for identification can be misleading as other tussock grasses have similar serrations.
The ligule is the key feature for identifying serrated tussock. To find it, trace down a leaf to its junction with the leaf sheath (i.e. the junction with the next leaf). Slowly separate and bend the leaf back, and a small, white hairless flap 1 mm long will protrude vertically.
Leaf basesThe leaf bases of serrated tussock are whitish and ‘shallot like’.
FloweringSerrated tussock generally flowers during mid to late spring, and the seeds develop in early to mid-summer. The time of flowering is variable from year to year, depending on seasonal conditions.
Seed headsThe seed head is a panicle (multi-branched seed head) up to 35 cm long with a weeping appearance when in full flower. At each junction of the seed head, there are two or three branches with a single seed on each branch, or alternatively another set of small branches with single seeds.
SeedsSeeds of serrated tussock are hard and small (1.5 mm long), with a ring of white hairs at one end and a twisted awn 25 mm long at the other.The awn is attached off-centre to the seed. At flowering the seed is encased in reddish-brown or purple bracts.
Root systemSerrated tussock has a deep, fibrous root system that makes pulling plants from the ground more difficult compared to other tussock grasses of similar size.
Similar looking tussock grassesA number of native grasses are often mistaken for serrated tussock. Use the following steps to distinguish serrated tussock from these similar-looking native tussock grasses:
Step 1Look for hairs on the leaf (without using magnification). If hairs are present, the plant is probably an Austrodanthonia species such as wallaby grass. Austrodanthonia pallida (red-anthered wallaby grass) has a large mass of hairs up to 3 mm long. If you cannot see hairs, proceed to Step 2.
Step 2Look at the leaf base and the ligule which can be found by removing the brown leaf sheaths. If the leaf base is purple and there are hairs near the ligule, the plant is an Austrostipa spp. (speargrass or corkscrew grass). Rough speargrass (Austrostipa scabra) has a ring of hairs accompanying a small ligule. If the leaf base is white, proceed to Step 3.
Step 3Take a close look at the ligule and compare it with the sketches in Figure A. If the ligule is white and hairless and the leaf is round (able to be rolled between the fingers), the plant is serrated tussock. If there is no ligule and the leaf is folded, the plant is Poa spp. (P. labillardieri, poa tussock or P. sieberana, snowgrass). Poa spp. have extensions on the top of the leaf sheath that are covered with fine spines.
Step 4Try to confirm the identification by locating the seed head or the seed and comparing it to the diagrams and photos in this Primefact. If you are in doubt as to the identity of the plant, seek advice from your district agronomist or local weeds officer. Erect seed heads are never found on serrated tussock but are common on Poa spp. (snowgrass, poa tussock); Austrostipa spp. (speargrass, corkscrew grass); Austrodanthonia spp. (wallaby grass); and Aristida spp. (three-awned speargrass).
Serrated tussock rarely grows in wet areas or under a heavy canopy of trees. Other species such as poa tussock are commonly found in wet areas, and snowgrass and red-anthered wallaby grass can be found growing under trees.
Most germination of serrated tussock seeds will occur in autumn in response to rain. However, it is possible for seeds to germinate at other times of the year. The germination capacity of newly formed seed varies between 74% and 91% over a 6-12 month period. Although most seeds will germinate within 3 years, very small quantities have been reported to remain viable for significantly longer periods (up to 20 years under laboratory conditions).
EmergenceSeedlings are weak competitors and they are unable to emerge from soil depths greater than 1.8 cm. In heavily infested areas, 4000 tussock seedlings can establish per square metre, but inter-plant competition reduces the number to about 15 per square metre after three years.
GrowthGrowth of serrated tussock seedlings is relatively slow compared to many desirable pasture species. As seedlings are not very competitive they are easily smothered by other more desirable pasture species (i.e. annual clovers). Established perennial grasses will not allow serrated tussock seedlings to establish during their first summer. Mature serrated tussock plants also grow slowly, producing the most foliage in spring and summer and the least in autumn and winter, when low temperatures limit growth.
The reproductive stages of serrated tussock are shown in Table 2.
Seed production occurs mostly in plants as young as 18 months old and possibly even in younger plants when conditions and seasons are favourable. It takes approximately 10 weeks for a seed head to develop. The number of seeds produced on each plant will vary depending on plant size and seasonal conditions. Medium-sized plants can produce around 50 000 to 80 000 seeds while large plants have been estimated to exceed 140 000 seeds per plant per year. A heavy infestation of serrated tussock could produce up to 930 million seeds per hectare.
Serrated tussock seeds are primarily dispersed by wind. The ripe seed heads break off at the base, and the whole seed head can then be carried considerable distances – it is estimated that seeds can be moved up to 10 km; however, seeds are suspected of being able to travel further under favourable conditions.
Seeds can be carried considerable distances in water (serrated tussock has been found on the banks of the Macquarie River, 60 kilometres downstream from the nearest infestation at the headwaters).
||Development of seed head
||Seed heads first appear as thick tillers in early to mid spring.
||Seed heads begin to emerge from these tillers.
||Most seed heads have fully emerged and opened, and have a purple tinge.
||Seeds reach the milky dough stage.
||Seeds reach the dough stage.
||Seed heads are fully developed and ‘weep’ over the tussock to the ground. When mature they break off at the base and are spread by wind.
Once the seed is dispersed serrated tussock is able to quickly colonise areas of bare ground or pastures that lack perenniality, have low cover and biomass of desirable species, are overgrazed or drought stricken. Drought conditions causing bare ground are particularly favourable for serrated tussock and can increase its invasive potential. The length of time for total colonisation will vary depending on soil type and rainfall.
On lighter soil types it is common for the infestation to increase from scattered plants to more dense populations within a few years. Heavier soil types tend to have a higher fertility and therefore a greater potential to have more competitive pasture species, enabling greater resistance to the establishment of serrated tussock seedlings. In some years serrated tussock has been known to seed twice in one year.
Nutritional value for livestock
Serrated tussock has extremely low nutritional value for stock compared to other more desirable pasture species. The digestibility (amount utilised by the animal) of the green leaf component from mature or seedling serrated tussock can range from 44% to 51% (5.5–7 MJ/kg DM metabolisable energy) compared to 70% to 75% (10–11 MJ/kg DM metabolisable energy) for the green leaf component of desirable pasture species (eg. cocksfoot, phalaris).
The dead leaf component from mature or seedling serrated tussock is commonly only 30% digestible (4 MJ/kg DM metabolisable energy) compared to approximately 40% digestible (approximately 5 MJ/kg DM metabolisable energy) for that of desirable pasture species.
Animals forced to graze serrated tussock will not meet maintenance requirements regardless of stock type or class. Minimum nutritional requirements for stock maintenance are 55% digestibility and 7.5 MJ/kg DM metabolisable energy.
Grazing trials in NSW have shown that sheep cannot live on a diet of mature serrated tussock. Due to its very low digestibility, the tussock foliage passes very slowly through the rumen and provides very few nutrients to the animal. If sheep are left to graze serrated tussock, they will lose weight and eventually die, despite the rumen being full of partly digested tussock foliage at death. A study in New Zealand using cattle revealed a similar trend. Two hundred steers were placed on 80 ha and were forced to graze serrated tussock to a height of 10 cm. This grazing pressure reduced seeding by 90%, but the steers lost weight.
Stock grazing dense serrated tussock for short to medium periods may require supplementation to provide both energy and protein to maintain the animal’s condition.
Due to its very low palatability, set stocking of paddocks containing serrated tussock can be to the detriment of more desirable pasture species present. When desirable species are selectively grazed and heavily utilised they will take longer to recover and respond to water, sunlight and nutrients. Desirable plant numbers may also decline if continual grazing pressure is applied.
Preventing establishment and spreadThere are several key principles involved in preventing new infestations. These include:
IdentificationLearn to identify serrated tussock and feel confident in your ability to do so.
Early interventionControl serrated tussock plants as soon as they appear and before they seed (including odd plants and light or scattered densities of plants). Delaying control will quickly lead to larger infestations which are more difficult and costly to control. Early intervention is the best way to avoid heavy production losses and high costs of control at a later time.
Keep pastures competitiveBare ground and a lack of competitive pastures provide serrated tussock with the ideal opportunity to colonise. Maintaining vigorous, competitive pastures through fertiliser use and sound grazing management will help prevent serrated tussock invasion. Continual vigilance in controlling scattered plants is particularly important to keep the weed at a manageable level. Extra vigilance is required when droughts break and early control of seedlings is then vital.
Keep introduced pastures vigorous and competitive. Incorporate grazing rests, conservative stocking rates and regular fertiliser application into pasture and livestock management plans. This allows desirable species to increase in size and become more competitive.
Encourage and maintain density and dominance of native grass species, particularly over summer, by managing grazing and allowing these grasses to flower and set seed each year. Continuous grazing, particularly at high stocking rates will encourage serrated tussock invasion.
Obstacles such as fences, trees, windbreaks or gullies can capture large volumes of seed heads. Seeds are then able to germinate forming new colonies of serrated tussock. Consider planting windbreaks along property boundaries to reduce the amount of seed blowing in. Dense vegetation, such as pine trees or native trees and shrubs, may help to reduce seed dispersal.
Revegetate unproductive areasOn unproductive land long-term consideration needs to be given to total revegetation with trees and/or complete retirement from agricultural production. Prior to trees forming a dense canopy serrated tussock is still able to invade.
Minimise soil disturbance
On light soil types minimal soil disturbance is strongly recommended. Avoid ploughing as mass seedling germination can occur.
Check vehicles and machineryEnsure vehicles and machinery are free of seed when moving into clean areas.
While livestock do not readily consume serrated tussock, the seeds can be passed via the gut or rumen if they do. In one study, wethers taken from an infested property passed an average of 4600 seeds per animal in the 10 days after removal. It is probable that most seeds passed this way are viable. Animals may also pick up seeds in hooves, fleeces or coats and transfer the seeds to other seed heads as nesting material.
Check fodder purchases (hay, silage or grain)
Serrated tussock can be easily spread through the introduction of fodder or hay containing serrated tussock seeds. Inspect hay or fodder for the presence of any weed seeds. Feed out areas should be monitored for germinating seedlings.
Develop a plan
Planning with the assistance of neighbours, council weeds officers and district agronomists will provide a structured approach to controlling and managing serrated tussock infestations. For more information on developing a plan please refer to the Serrated Tussock National Best Practice Management Manual.
Management and control
A number of herbicides are registered for the control of serrated tussock in NSW. The most widely used herbicides are those that contain either glyphosate or flupropanate. The most appropriate herbicide and rate for your situation will depend on the size and density of the infestation, the time of year, the presence of desirable species, soil type, climate and topography.
Native and introduced pasture species vary in their tolerance to herbicides. It is therefore important to identify the pasture species present before undertaking chemical control.
Reliance on herbicides alone in situations where competitive pasture species are not maintained is not effective and can also lead to herbicide resistance with long term use.
Flupropanate herbicides are Group J herbicides and are available under a range of product names. They have been used for many years and will selectively remove serrated tussock from established introduced pastures; however, some common native pasture species such as weeping grass (Microlaena spp.), wallaby grass (Austrodanthonia spp.) and speargrass (Austrostipa spp.) are susceptible to flupropanate and may be damaged or removed from the pasture completely. Other native species such as kangaroo grass (Themeda australis) and redgrass (Bothriochloa macra) are more tolerant to this herbicide. Legumes such as sub clover and white clover are also susceptible to flupropanate.
Flupropanate is a residual herbicide that can remain active in the soil for up to two years. Residual activity is dependent on how much rainfall is received after spraying. Under very low rainfall or drought conditions residual activity will be longer. Light sandy soils leach the herbicide more quickly than heavy clay soil types. Flupropanate will continue to kill seedling serrated tussock until 100mm of leaching rainfall has fallen, after which the residual effect will be gone.
Depending on your soil type, flupropanate can be used at lower than label rates to control large tussocks and seedlings: see Australian Pesticide and Veterinary Medicines Authority (APVMA) permit PER9792 which expires on the 30 November 2015. Copies of the permit can be viewed on or downloaded from the APVMA website www.apvma.gov.au).
Flupropanate takes several months to kill serrated tussock, therefore, it may not stop seed production when it is applied after mid-August. In this case, glyphosate or a mixture of glyphosate plus flupropanate can be applied to prevent seed production and kill the plants. (AVPMA permit PER9792). To ensure that seed set is halted, spraying must be done two to four weeks before the start of seed head emergence (as indicated by thickening of the tillers).
Glyphosate herbicides are non selective and are Group M herbicides. They are available under a range of product names. The main applications of glyphosate herbicides in a serrated tussock control program include an application in spring in preparation for crop or pasture establishment in the following autumn; and carefully timed applications that use the herbicide selectively to preserve existing desirable pastures and prevent serrated tussock from seeding.
Glyphosate is the preferred herbicide where preparing a paddock for cropping or establishment of new pasture on serrated tussock infested land. Spray paddocks in spring for a complete knockdown of serrated tussock and other weed species. Paddocks can then be left fallowed in order to accumulate adequate moisture over the summer months. A second application of glyphosate after the autumn break is necessary to control any new weed growth before sowing pasture or crop in autumn.
Glyphosate can be used all year. Best results occur when tussocks are green, actively growing and not under stress. Applications should be made well before seed set. Avoid using glyphosate under dry soil conditions and also early morning when frosts and dew are present or when plants are covered with dead plant material. It is essential to get good spray coverage of all green leaf material otherwise a complete kill may not be achieved.
Glyphosate has no residual effect and subsequent germinations of serrated tussock may occur after spraying.
Glyphosate can have unreliable effects when applied to mature serrated tussock growing on very heavy, fertile basalt soils in areas with low rainfall or under conditions where soil moisture is limiting.
Spot spraying using flupropanate or glyphosate herbicides can be used to control individual tussocks or small patches on all types of terrain. Spot spraying can be undertaken throughout the year when conditions are favourable, however; it is essential to spray before plants set seed (seedlings can set seed at 18 months of age). Both flopropanate and glyphosate herbicides can damage desirable pasture species hence care must be taken to apply herbicide only to the tussock plants.
A spray shield can be fitted to a handgun to minimise off-target damage. Make sure spot spraying equipment is calibrated to ensure the correct rate of herbicide is applied. A coloured dye can be added to the herbicide to indicate which plants have been sprayed. It will still be necessary to reinspect spot sprayed paddocks to check for seedling tussocks or smaller plants that may have been missed.
Herbicides can be applied using a boomspray or aircraft to larger areas heavily infested with serrated tussock.
Flupropanate is appropriate for aerial spraying and has less potential for non-target damage (particularly to trees) than glyphosate.
Wipers can be used to selectively remove large tussocks from pastures, but only where the tussocks are higher than desirable pasture species. Both flupropanate and glyphosate are suitable to use in this way. Before using the wick wiper the pasture must be grazed to reduce the height of the desirable species in order to minimise damage.
Wiping is not often used by landholders, as it is only effective on large tussocks and it is not feasible in non-arable terrain where rocks, stumps or logs are present. Smaller tussocks will be missed and these then set seed. The technique needs to be repeated as the smaller tussocks mature.
The efficacy of this technique on large plants may be improved by passing the wiper a second time (in the opposite direction) over the tussocks.
Herbicide resistance is the ability of a plant to survive and reproduce after the application of herbicide that would normally be lethal.
Resistance to label rates of flupropanate was first identified in Victoria in 2002 and has since been confirmed at Armidale and Goulburn in NSW. There have been no reports of serrated tussock being resistant to glyphosate.
Flupropanate resistance has occurred following the continual application of the herbicide on the same land over a number of years.
The development and spread of herbicide resistant plants then means that serrated tussock becomes difficult to control. There are a number of ways to avoid developing herbicide resistance on your farm. These include:
Rotate herbicide groups
All herbicides belong to a herbicide group (Group A-R and Z). Herbicides within a group have the same mode of action. Herbicide resistance can be avoided by not relying solely on herbicides from a single group. In the case of controlling serrated tussock do not use flupropanate (Group J) continuously over the same areas and rotate with glyphosate (Group M) whenever possible.
Reduce the population level
The likelihood of resistance developing is higher when there are large populations of plants being treated with herbicide.
Stop seed set
The presence of one resistant plant will produce resistant seed further increasing the resistant plant population.
Use integrated control techniques
Consider other methods such as mechanical control, cropping (where appropriate), pasture establishment, chipping isolated plants, forestry and grazing management and fertiliser.
Monitor sprayed areas for resistant plants
The survival of any mature plants and the emergence of seedlings in a short period of time following a blanket spray treatment should be suspected as potential herbicide resistance.
For more information on herbicide resistance refer to the Primefact ‘Recognising, managing and preventing herbicide resistance in serrated tussock’.
Chipping with a mattock is suitable for removing individual plants scattered across clean paddocks. Isolated tussocks can be chipped year round, preferably before they seed. Tussocks chipped in full flower should be removed from the paddock and disposed of by burning. When conditions are wet soil clods attached to the exposed roots should also be removed to prevent survival. Excessive soil disturbance by chipping can encourage germination of seedlings. In this situation pasture seed and fertiliser should be scattered in the disturbed area as an effective means of providing competition.
Cropping prior to pasture establishment
Cropping can be used prior to pasture establishment to reduce the serrated tussock seed bank. On suitable soils (eg. those with a low erosion risk and good soil depth) it is preferable to crop for at least one year prior to sowing a new pasture. Suitable crops may include oats, winter wheats and forage brassicas. Dual purpose cereals are useful in offsetting the costs of pasture establishment through the grazing and grain values obtained. For specific information on crop suitability, sowing rates, time of sowing and crop nutrition consult the latest Winter Crop Variety Sowing Guide available from Industry & Investment NSW and your local agronomist.
It is preferable to use a knockdown herbicide such as glyphosate in the spring prior to sowing. Disc ploughs are most effective in breaking up tussock clods however, on some soil types eg. those with excessive slope or shallow top soils, direct drilling is the preferred method of establishment and ploughing should be avoided.
The paddock should remain in fallow over summer to accumulate moisture in the soil profile prior to sowing the crop. After the autumn break a knockdown herbicide treatment will be required to control any germinating serrated tussock seedlings, annual grasses and broadleaf weeds. Depending on crop variety choice, sowing should normally commence in autumn following the break.
Sowing new pastures
A permanent pasture based on perennial grasses as well as legumes is one of the most effective means of preventing serrated tussock from encroaching on land. If there are few desirable pasture species present in the paddock then it will be necessary to sow a new pasture. Advice should be sought on the most suitable species and cultivars to sow and the most appropriate method of sowing for the country under consideration. It is important to remember that successful establishment and persistence of the perennial grass will act as the major deterrent to serrated tussock reinvasion so good establishment is essential.
If direct drilling, it is essential to have minimal trash levels to allow ease of establishment. High levels of trash from crop stubbles or dead serrated tussock plants should be reduced by grazing, burning or a combination of both well in advance.
On non arable land it will not be possible to sow a new pasture via ground means. Aerial seeding introduced pastures is an option on such country, however, it is highly unreliable especially in areas of low rainfall and low soil fertility. The risk of failure is greater than other establishment techniques such as direct drilling or cultivation. Consider the economics very carefully and the potential returns before attempting to sow a pasture in difficult terrain. Seek advice from your agronomist if considering this option.
Prior to sowing ensure that any herbicide residual period has lapsed. In the case of flupropanate 100 mm of leaching rainfall must fall before attempting to establish a new pasture or crop.
Under some situations, serrated tussock seedlings may reinfest a new pasture. If this occurs, a lower than label rate of flupropanate applied in the second spring or summer after sowing can be used to kill tussock seedlings (up to 18 months old) with minimal damage to the pasture. (see APVMA permit PER9792). This treatment is more cost effective than spot spraying the tussocks at a later age. Using low rates will ensure all seedlings will be killed. Calibration of spray equipment is essential to minimise off-target damage.
Long-term management should aim to maintain the vigour, competitiveness and dominance of desirable species to assist in the exclusion of serrated tussock. Both strategic grazing management and fertiliser use will help to maintain the pasture in a competitive state.
Grazing newly sown pastures
It is preferable not to graze newly sown pastures for one year. However, under good soil moisture conditions and once the plants become well anchored, a quick, light grazing preferably with cattle in spring can promote tillering.
The pasture should always be spelled in the first summer to allow grasses to set seed. If the pasture is not spelled in this period, then pasture establishment and overall success may be compromised.
Graze the pasture in the autumn after sowing to remove dead plant litter and allow subterranean clover to germinate. Lenient grazing is critical followed by spelling in the first two or three spring-summer periods to ensure plants increase in size and become well established. Increased groundcover and setting of seed for recruitment is necessary to exclude serrated tussock for the longer term.
Grazing management should be aimed at promoting seed set and seedling recruitment of preferred pasture species. Ensure adequate leaf area is maintained in drought, to enable pastures to recover more rapidly when conditions improve.
Grazing existing pasture
Existing pastures susceptible to invasion need to be managed to maintain competitiveness and prevent serrated tussock establishment. Attention should be given to maintaining ground cover at all times. Trials have demonstrated that greater than 2 t/ha herbage mass (measured in spring) and 100% groundcover prevented seedling establishment even when additional serrated tussock seed was added to the soil surface.
Generally the higher the ground cover and pasture herbage mass the more resilient the pasture will be to serrated tussock invasion, particularly during autumn when most serrated tussock recruitment occurs. Grazing management using pasture herbage benchmarks can be used to maintain higher levels of ground cover and herbage mass.
For more information on how to assess pasture herbage mass, pasture benchmarks and grazing management strategies, courses such as PrograzeTM are run by local District Agronomists and Livestock Officers with NSW Department of Primary Industries.
In native pastures it is highly desirable to have a high perennial density to limit serrated tussock seedling invasion. Grazing should aim to promote a high density of perennial grasses to compete with serrated tussock seedlings for moisture during the first summer after they germinate. Redgrass (Bothriocloa macra) has been shown to reduce the establishment of serrated tussock seedlings compared to areas where it or another perennial was absent.
Regular applications of essential nutrients will help ensure introduced species maintain vigorous growth rates and persistence. Phosphorus and sulphur are commonly the two major nutrients deficient in soils and limiting pasture production. Regular soil test on the established pasture can help determine future fertiliser requirements.
Similar to introduced pastures, modified native based pastures may also require the addition of fertiliser to maintain them in a competitive state.
For advice on fertiliser rates and application, consult your local agronomist.
Follow up control
Follow up control programs are essential in order to achieve success in eliminating serrated tussock. Failure to revisit sprayed areas particularly in moderate to heavy infestations can result in serrated tussock again becoming the dominant species within a few years.
In areas of low soil fertility and low rainfall, afforestation can be an effective way of reducing serrated tussock establishment and spread in the long term. Be aware that it will take many years for trees to become large enough to be an effective means of suppressing serrated tussock.
Pinus radiata, for example, or other trees that provide dense shade can help to control serrated tussock. Establishing pine trees or other trees among serrated tussock can be difficult. Either the serrated tussock has to be sprayed with herbicide, or the soil cultivated or ripped before planting. Depending on rainfall and fertility pine trees may take 5 to 8 years to stop the serrated tussock from seeding and 8 to 12 years to kill it. During this period serrated tussock will still require control through chemical or physical means.
Label rates of flupropanate can be used to control serrated tussock with minimal damage to juveniles of acacia and eucalyptus species used for revegetation.
Commercial forestry may be an option in some areas, however seek expert advice before investing in such a project.
Serrated tussock was declared a target for a biological control program in 1998. Several surveys where undertaken to identify potential agents in Argentina and South America. Three fungi where investigated including Puccinia nasellae (a rust fungi), Ustilago spp. (a smut fungi). and Corticum spp. (a Basidiomycete fungus).
Unfortunately progressing these species to release in Australia was not possible as they where found to impact on some native grasses (Austrostipa spp.) Subsequently, no biological control agents are available for serrated tussock.
Serrated tussock is declared a Class 3 or Class 4 noxious weed in many areas of NSW. In areas where it is declared Class 3 the plant must be fully and continuously suppressed and destroyed. In areas where it is declared Class 4, the growth of the plant must be managed in a manner that reduces its numbers spread and incidence and continuously inhibits its reproduction and the plant must not be sold propagated or knowingly distributed.
The responsibility for control of noxious plants and appropriate disposal of weed plant material on private land rests with the owner or occupier of the land. Failure to do so could result in the local control authority issuing a weed control notice, court action and a fine.
Control of noxious weeds on public land must be undertaken adequately to prevent the infestation spreading to adjoining land. Community members can assist the control of this weed by notifying the local control authority of any known infestation of serrated tussock on public land. In addition, for both weed classes: the plant must not be sold, propagated or knowingly distributed. Contact your local control authority for more information.
This publication revises and replaces Primefact 44 First Edition (May 2006).
Authors: Linda Ayres and Fiona Leech
Technical reviewers: Warwick Badgery, Luke Pope, Birgitte Verbeek and Phil Graham
References and further reading
- 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 WB, Kemp DR, Michalk DL, King WM (2005) Competition for nitrogen between Australian native grasses and the introduced weed Nassella trichotoma. Annals of Botany 96, 799-809.
- Badgery WB, Kemp DR, Michalk DL, King WM (2008a) 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 WB, Kemp DR, Michalk DL, King WM (2008b) 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, Scott, M (2010). Weed Control in Lucerne and Pastures 2010. Industry and Investment NSW.
- Osmond R, Verbeek M, McLaren DA, Michelmore M, Wicks B, Grech CJ and Fullerton P (2008). Serrated tussock - National Best Practice Management Manual. Victorian Department of Primary Industries. www.weeds.org.au/WoNS/serratedtussock