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- Declared in NSW under the Noxious Weeds Act 1993
Cenchrus incertus (current status)
Cenchrus longispinus (current status)
Contacts and Further InformationIf you find this weed please help to prevent its further spread by contacting your local Council Weeds Officer for positive identification and further assistance.
Alternatively call the NSW Weeds Hotline on
1800 680 244 or send an email to email@example.com
Spiny burrgrass (Cenchrus species)
Spiny burrgrass (Cenchrus species) is a summer-growing grass found throughout the drier areas of Australia, often on disturbed soils. There are four species of Cenchrus classed as troublesome weeds in NSW, C. caliculatus, C. echinatus, C. incertus and C. longispinus, with the latter two declared noxious weeds throughout NSW.
Not all species of Cenchrus are undesirable. There are 10 species in Australia, two of them native. Several, such as buffel grass (C. ciliaris), slender buffel grass (C. pennisetiformis) and birdwood grass (C. setiger) produce soft burrs and can be beneficial tropical and subtropical pasture species. These pasture species are also considered invasive weeds of natural rangelands in some parts of Australia.
The difficulty in identifying individual species has led to considerable confusion in botanical identification and in the use of common names. For this reason the name spiny burrgrass is used generally in this Primefact.
There are numerous other common names used to describe these species including bohena beauty, field burr, sandburr, innocent weed, gentle Annie and hedgehog grass.
Spiny burrgrass is commonly found in drier regions with rainfall of 250 to 600 mm. It prefers sandy to light soils and is generally not found on heavy clay soils. It readily establishes on disturbed sites such as roadsides, creeks and riverbanks.
Spiny burrgrass has spread extensively throughout NSW because of:
- large numbers of travelling stock, foxes and kangaroo
- movement of fodder
- an increase in areas of stubble from cereal crops that provide little competition and an ideal situation for the rapid build-up of the weed
- lack of pasture competition in low rainfall areas due to variable seasons
- road graders, slashers and vehicle tyres
- the use of contaminated sand for building roads, amenity and construction purposes
- irrigation water.
Spiny burrgrass is a summer-growing grass that forms large clumps and generally grows to 30 cm but can reach 60 cm or more.
The species C. incertus can be either annual or perennial depending on the environment. The other Cenchrus weed species are annuals. In many areas of NSW, C. incertus is usually killed by frosts and therefore acts as an annual.
For each plant, several stems grow from the base and can be either erect or spreading. The leaves can be up to 20 cm long and are smooth but sometimes twisted and finely serrated. The roots are fibrous and usually shallow but can be more than 30 cm deep in some soils. The flowers are a spike-like panicle, 3–8 mm long and consisting of up to 40 ‘burrs’. The burrs are straw-coloured, sharply pointed, rigid, with finely barbed spines up to 7 mm long and a purplish colour in C. longispinus and up to 5 mm long in C. incertus.
Spiny burrgrass is a weed because of its sharp and clingy burr, ability to spread rapidly and tendency to develop into dense infestations in favourable conditions. It is also difficult and expensive to manage, especially in marginal rainfall areas.
Mature burrs cause a range of problems such as:
- injury to stock causing swellings and ulcers in the mouth
- injury to people and dogs
- clinging to wool and penetrating the skin of stock, reducing the value of both
- shearing difficulties, which often attracts penalty rates as working with contaminated wool requires leather gloves and/or aprons.
- inconvenience and discomfort to workers in irrigated crops such as vegetables, vines and citrus, and
- contamination of dried fruit and hay.
Seeds are normally produced from late spring to late autumn depending on available soil moisture.
There are up to three seeds produced by each “burr” resulting in each plant producing up to 1000 seeds. The first-formed, or primary seed, is the largest and is capable of germinating within a few months of maturity. The other seeds, or secondary seeds, are usually dormant for up to three years.
Spiny burrgrass has several germination regulating mechanisms to ensure its survival during hot, dry summers.
The germination process is slow. It is reliant on extended periods of moist soil and is suppressed by light and high temperatures. The seed needs to be buried a few centimetres to maximise germination.
Germination generally occurs in spring allowing seedlings to establish during a period favourable for growth but it can occur at any time of the year provided soil temperature and moisture are suitable.
Dormancy of secondary seeds is prolonged by exposure to light on the soil surface or by burial under dense vegetation.
Exposure of seed to high or low temperatures will also induce dormancy with the optimum temperature range for germination being 10°C to 20°C.
Both primary and secondary seeds have the ability to establish from depths of up to 20 cm below the soil surface.
In NSW, most plants die in autumn or early winter, although in mild winters some plants can survive and produce burrs early in the following spring.
|Life cycle stage||Time of year|
|Germination||Spring to early summer|
|Active growth||Late spring to early summer|
|Development of burrs and seed set||Late spring to late autumn|
|Death of plant
||Autumn to early winter|
The major spread of this weed is by seed. The seed is well equipped for spread because of the barbed spines on the burr, which detach easily from the mature plant.
Control and Management
Integrated weed management
The key to the effective control of spiny burrgrass is to prevent seeding and exhaust any reserves of seed in the soil. This can be achieved through integrating cultivation, herbicide application, increasing competition through good pasture establishment and management and cropping.
A management strategy should consider any physical and climatic limitations and cover a three to five-year period.
Prevent spiny burrgrass from spreading by: excluding livestock from infested areas especially when burrs are likely to adhere to livestock and thoroughly cleaning any vehicles or machinery used on site before leaving.
It is important to restrict vehicle access and/or notify anyone who may be accessing the infested site to ensure that they also practice good hygiene.
Control of infestations on roadsides
Infestations can occur as a result of moving livestock, contaminated road graders or road building material.
The integration of several control options is necessary in these situations.
The application of non-selective herbicides can be followed by cultivation to remove established seedlings or burning the dead plants, in suitable conditions, to destroy the remaining seed heads. It is also useful to put up signs where infestations occur to alert others of the presence of spiny burrgrass and of restrictions on moving machinery or livestock through the area.
Once the seed reserves have been depleted, summer-growing perennial grasses such as Consol lovegrass, Rhodes grass or kikuyu should be established along roadsides to provide competition to germinating weed seedlings.
Maintaining vigorous perennial pastures is critical to prevent spiny burrgrass from becoming dominant.
Spiny burrgrass does not establish readily in situations where there is competition from other vegetation.
Good ground cover in spring and summer will limit germination and seedling establishment.
Management of existing and native naturalised pastures should aim to maintain perennial grass content and ground cover. Identify the species present, their growth cycles and their response to grazing and fertiliser to formulate a management regime that will maximise their competitive behaviour.
Establishing a new pasture
Establishing perennial pastures is expensive so thorough preparation and research into suitable species and varieties is required. The establishment of adequate plant numbers is the first step to a successful pasture. Seek advice from your agronomist on the best pasture establishment steps for your situation.
Competitive summer grasses such as Rhodes grass, Premier digit and Consol lovegrass have proven successful in controlling spiny burrgrass on sandy soils. These grasses are summer-growing perennials and are excellent competitors where the weed is a problem. They establish readily, are drought-tolerant and are reasonably palatable to stock (depending on grazing management).
Ideally, these summer grasses should be sown with an annual legume suitable to your area such as a subterranean clover, medic or serradella. Lucerne may also be included if the soils are not too acidic.
In the vegetative stage, spiny burrgrass is readily eaten by livestock. In paddocks dominated by spiny burrgrass heavy grazing may be used to suppress growth and production of burrs as a short term management strategy. However, it has limited value if the spiny burrgrass infestation is sparsely scattered throughout a paddock.
Stock have the potential to spread infestations so it is important to remove stock before seeding commences.
In paddocks that have sparse infestation overgrazing must be avoided. Every effort must be made to keep pastures competitive to prevent dominance by spiny burrgrass.
Timely cultivation to bury the burr or remove surface cover will increase germination and lead to the rapid exhaustion of dormant seeds in the soil.
Follow-up cultivation or the application of an appropriate knockdown herbicide is required to remove the resultant seedlings before they set seed. Under warm, dry conditions this might only be four weeks after germination.
If using only cultivation, repeated workings over a prolonged period will be required to control subsequent seedlings. Intermittent cultivation will create conditions which are ideal for the germination, growth and reproduction of spiny burrgrass, potentially leading to dense infestations becoming established. Avoid over-cultivation as this can increase the risk of soil erosion and soil structural problems such as compaction or surface crusting.
In arable situations a management strategy may involve one or two cultivations during spring and summer combined with fallow spraying. Alternatively, the cultivations may be followed by the application of a pre-emergent herbicide and sowing with a winter crop such as wheat, barley, triticale or lupins.
Some landholders have eradicated spiny burrgrass by using a combination of cultivation and knockdown herbicides for three to five years to prevent any plants present from seeding.
Cropping prior to pasture establishment
It is preferable that the seed reserves of spiny burrgrass be reduced as much as possible before sowing a competitive pasture. This can be achieved by either a period of winter cropping, incorporating the use of a pre-emergent herbicide followed by sowing an appropriate winter crop, or a period of summer cropping, incorporating the use of a pre-emergent herbicide followed by sowing an appropriate broadleaf crop (e.g. cowpeas).
A post emergent application of a selective grass herbicide might be required to control any burrgrass that has escaped the pre-emergent herbicide.
Herbicides can play an integral role in the control of this weed but are best used in a strategy incorporating cultivation, crop rotation and pasture improvement.
Pre-emergent herbicides with soil residual properties have been successful in the control of spiny burrgrass in broadacre crops such as cotton, sunflowers, soybeans, pulses, lucerne and vegetables. However, because seeds can germinate from depths of up to 20 cm, pre-emergent herbicides are not always completely effective. In the event of germination, post-emergent grass herbicides can be considered in broadleaf summer crops and lucerne. Obtain advice from your local agronomist before undertaking this option.
Non-selective knockdown herbicides will kill existing plants but repeated applications are necessary to control subsequent germinations. These herbicides are best used in situations such as fallows, along fencelines and along roadsides. They are best applied when the weed is actively growing (late spring/early summer) before the burrs are produced (see Table 1).
Only a registered herbicide used according to the directions on the label should be used to control a weed. For the recommended herbicides to control spiny burrgrass, refer to the NSW Department of Primary Industries (DPI) publications Noxious and Environmental Weed Control Handbook, Weed Control in Pastures and Lucerne, Weed Control in Summer Crops or Weed Control in Winter Crops (fallow situation).
Control in permanent horticulture
Spiny burrgrass can be a problem in permanent horticulture, particularly as a contaminant of dried fruit.
Management can be difficult, particularly in irrigation situations, but will generally involve the integration of control options such as close mowing of cover crops, inter-row cultivation, physical removal of isolated plants, the application of non-selective herbicides and good farm hygiene practices to prevent the spread of burrs.
Dried fruit producers can refer to the ADFA Dried Fruit Manual produced by the Australian Dried Fruit Association, Mildura, Victoria.
Spiny burrgrass is a Class 4 noxious weed under the NSW Noxious Weeds Act 1993 in many areas of NSW.
Class 4 control requirements are that ‘the growth of the plant must be managed in a manner that reduces its numbers spread and incidence and continuously inhibits its reproduction’.
The responsibility for the control of noxious weeds on private land rests with the land owner or occupier of the land. This responsibility extends to the middle line of any adjacent watercourse, river or inland water (tidal or non-tidal).
Contributing authors: C. Mullen, J. Dellow, A. McCaffery.
This Primefact is an updated edition of Agfact P7.6.21 Spiny burrgrass.
Technical reviewers: A. Storrie, K. Pengilley, Birgitte Verbeek.
- Parsons, W.T. and Cuthbertson, E.G. 2001, Noxious Weeds of Australia, second edition, CSIRO Publishing, Collingwood, Vic.
- Johnston, W.H. 1989, ‘Consol lovegrass (Eragrostis curvula complex) controls spiny burrgrass (Cenchrus spp.) in south-western NSW,’ Australian Journal of Experimental Agriculture, 29, 37–42.
- Twentyman, J.D. 1974, ‘Control of vegetative and reproductive growth in sand burr (Cenchrus longispinus),’ Australian Journal of Experimental Agriculture and Animal Husbandry, 14, 764–770.
- Spiny burrgrass, Integrated Weed Management fact sheet, Cooperative Research Centre for Australian Weed Management.