Perennial tussock grass with erect or drooping leaves, which grows up to 70 cm high and 80cm wide and forms dense clumps
Stem is swollen just above ground level – like a shallot. Other similar looking tussocks have purplish colouration at their leaf bases
Light green or yellowish-green leaves are thin and tightly rolled; they do not break when pulled. When fingers are run down the leaf, they feel needle-like and very tough
Leaf sheaths are white to light brown. Ligule is short (1 – 2 mm), white, hairless and obvious when the blade is pulled from a younger leaf. Auricles are absent
Similar looking tussocks have no ligule or a ligule with hairs
Plants usually flower between October and early summer when they have a purplish tinge. Flowering stems can be up to 1 m tall
Flowerheads are open, with a branched seed head 25 – 95 cm long, and produced between November and January
Ripe seeds are purplish with a 3cm long bristle
Roots are deep, matted and fibrous. They have been found growing 1.7 m below the soil surface.
Biology
Origin
Nassella tussock originated from South America and has been present in New Zealand since 1860
It has been under control in New Zealand since the 1940s. In 1946 the Nassella Tussock Act became law – the only Act referring to a single weed species
Prevalent in North Canterbury and Marlborough, where it can form dense stands which are difficult to manage
Grows well on steep, dry, rugged sunny slopes, ridges and knobs, along stony riverbeds, stream banks and river terraces
Establishes well on overgrazed, dry bare land. Burning can enhance seed production
Currently tussock numbers are stable in North Canterbury. This suggests that grubbing is stopping numbers from increasing, but some plants are missed and these produce enough seed and hence seedlings to maintain tussock numbers.
Life cycle
Nassella tussock seeds germinate and seedlings establish in autumn, although seedlings can establish at any time of the year
Germinate in late autumn or winter, when adequate rainfall increases seedling survival
Most seedlings appear to grow from the seeds of flowering plants rather than from the seedbank. Therefore plant numbers are more likely to increase from seeds produced from year to year rather than from seeds in the seedbank
Seeds are produced and become viable from late spring (November), with most produced in December and early January. Some seeds are viable when the seed heads first emerge from the leaf sheath. Once a plant has been grubbed, seeds do not continue to ripen
Seeds are spread by the wind and can travel as far as 16 km
Seeds are also transferred to other properties by livestock, machinery, clothing and on milled plantation logs
Each tussock plant can produce up to 100,000 seeds
Seeds can survive passage through sheep.
Benefits
No reported benefits.
Impacts
Nassella tussock can be seriously invasive, completely dominating low-producing grassland. Pasture carrying capacity can be significantly reduced because the leaves are unpalatable and indigestible
Sheep avoid grazing older tussocks when possible, but may graze younger plants
Because of its poor nutritional quality, sheep can lose condition on infested pastures. If forced to eat tussock, they will lose weight and can die as they cannot properly digest the leaves
Nassella tussock seeds can contaminate and damage fleeces and hides of sheep, adding to production losses.
Control
Combinations of cultivation, herbicides, fertilizer, oversowing and removing stock have been effective in reducing tussock numbers
Control during early invasion may be successful. If a farm becomes seriously invaded, nassella is very difficult and costly to control
Plants are more visible just before the autumn break
Control is very difficult on land that is infertile, cannot be cultivated, and is in a low rainfall area.
Grazing management
Grazing of nassella tussock by sheep and cattle does not control it, although it may to some extent reduce seedling densities and limit seed production
Cattle and sheep cannot digest the leaves and they avoid mature plants. This causes overgrazing of desirable species and leads to further spread of nassella tussock.
Pasture species/cultivars
Sowing perennial pastures can help to control nassella tussock, as long as the pasture is grazed and fertilised to favour the perennial species and maintain high levels of ground cover. Note: Ryegrass does not compete well with nassella tussock.
Cocksfoot provides better competition
Going through a cropping phase for two years before sowing (if the land can be cultivated) can reduce tussock seed numbers
Note that appropriate fertiliser application is very important in helping the sown pasture species to outcompete tussock seedlings.
Chemical control
Flupropanate is a selective and residual herbicide for nassella tussock and Chilean needle grass. The length of residual control depends on rainfall and soil type. (Always read the product label before applying)
Studies are underway in Canterbury to measure flupropanate efficacy and selectivity. In pasture dalapon or glyphosate can be used on dense infestations. (Always read the product label before applying)
Spot spraying from a boom spray or by aerial application is the most effective method to reduce dense growth of the tussock.
Mowing / grubbing
Most seedlings come from seed produced by flowering tussock plants, not from seed in the soil from previous years
Preventing existing tussocks from seeding stops tussock numbers increasing and eventually leads to declining numbers
Tussocks must be grubbed before the seed head emerges to stop fresh seeds from being produced
Individual plants can be grubbed but if the roots are not removed completely, they may re-grow
Grubbing is the most effective method of eradicating nassella tussock as long as plants are fully removed.
Biocontrol
No biological control agents are available for controlling nassella tussock.
Further information
References
Bourdôt GW, Hurrell GA, Saville DJ 1992. Eradication of nassella tussock (Nassella trichotoma), an unlikely outcome of grubbing. New Zealand Journal of Agricultural Research 35: 245-252.
Campbell MH 1998. Biological and ecological impact of serrated tussock (Nassella trichotoma (Nees) Arech.) on pastures in Australia. Plant Protection Quarterly 13: 80-86.
Campbell MH, Nicol HI 1999. Seed dormancy in serrated tussock (Nassella trichotoma (Nees) Arech.) in New South Wales. Plant Protection Quarterly 14: 82-85.
Campbell MH, Vere DT 1979. Area, distribution and cost of serrated tussock in New South Wales. Agricultural Gazette of New South Wales 90: 8-10.
Champion P, James T, Popay I, Ford K 2012. An illustrated guide to common grasses, sedges and rushes of New Zealand. New Zealand Plant Protection Society, Christchurch, New Zealand. 208 p.
Cook C 1998. The transmission of serrated tussock (Nassella trichotoma) seeds through the sheep rumen and their viability after ingestion. Plant Protection Quarterly 13: 93.
Lamoureaux SL, Bourdôt GW, Verkaaik M 2006. Outsmarting nassella tussock – answers to common questions based on recent research findings. Proceedings of the Fifteenth Australian Weeds Conference, Preston C, Watts JH, Crossman ND Eds. Weed Management Society of South Australia, Adelaide, South Australia. Pp. 883-885
Miller L 1998. Management of serrated tussock in farming areas. Plant Protection Quarterly 13: 91-93.
Vere D, Jones R, Dowling P, Kemp D 2002. Economic impact of Vulpia in temperate pasture systems in south-eastern Australia. Australian Journal of Experimental Agriculture 42: 465-472.
Vere DT 1977. Superphosphate essential for control of serrated tussock and St. John’s wort. Agricultural Gazette of New South Wales 88: 13.
Vere DT, Campbell MH 1984. Economics of controlling serrated tussock in the Southeastern Australian Rangelands. Journal of Range Management 37: 87-93.
Young S 2013. New Zealand Novachem agrichemical manual. Agrimedia Ltd., Christchurch, New Zealand. 767 p.
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