Black roly-poly (Sclerolaena muricata)

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Impact

Black roly-poly is a native plant of the Chenopodiaceae family, which includes other roly-poly plants, saltbushes and crumbweeds. It is regarded as a weed because it is generally not eaten by livestock due to the length of its spines, its burrs and spines contaminate wool, and it competes with plants that do provide feed. Black roly-poly has similar impacts to galvanised burr (Sclerolaena birchii) but is less likely to be grazed due to the greater length of its spines.

Dense infestations occur periodically, causing concern to graziers as it reduces wool values by causing vegetable fault. Spines that become detached from the burrs are problematic for wool-processing as they can become aligned with the wool fibres in spun yarn. Galvanised burr is only one of many species that can cause this type of fault in wool.

The spines and burrs are a considerable nuisance to shearers, stock and working dogs. At times when shearers are in high demand, they may choose to avoid shearing where sheep are carrying large numbers of burrs. Dense infestations also impede stock movement and block cultivation machinery.

Distribution

Black roly-poly is generally restricted to central and western areas of NSW and Queensland, and grows primarily on clay and clay loam soils. Due to the greater moisture holding capacity of these soils black roly-poly can be found in more arid areas than galvanised burr (Sclerolaena birchii).

Spread

Black roly-poly is a short-lived perennial. Seeds germinate in autumn after rain and plants develop a deep tap root during winter. 

Mature plants flower throughout the year. Seed develops within the spined woody burr that is firmly attached to the stem. Each burr contains only one seed but large bushes produce many burrs. Mature seed is sealed within the burrs and receives no sap flow from the mother plant allowing seeds to remain viable after the plant itself dies.

Mature plants are usually short lived. Many plants die within two years and few plants survive for more than four years. When a plant dies its tap root breaks allowing the dead bush to roll in the wind. Seeds are distributed as stem segments and burrs break off. Dead bushes commonly accumulate along fencelines. Stem pieces and burrs can also be spread by animals.

The woody burrs must breakdown enough to allow water to enter so that the seed can germinate. This process takes between 1 and 4 years depending on whether the burrs remain on the surface or are buried.

Over a period of years the density of populations will wax and wane. Numbers of plants fall close to zero during long droughts and rise sharply when seasonal conditions are more favourable to germination and growth. The slow breakdown of the woody burrs during long droughts can create large numbers of viable seeds in the soil (the seedbank).

Description

Black roly-poly is a hemispherical, short-lived, perennial shrub about 1 m in height and diameter, with slender tangled branches.

Flowers are solitary in the leaf axils and flowering occurs most of the year.

Fruiting bodies (burrs) are tube-like, 1-2.5 mm long with an angled base, with 5 slender spreading spines at the top. The three longest spines are 4-10 mm long. The two shorter ones occur close together, often joined at the base.

There are three varieties of black roly-poly in NSW: S. muricata var. muricataS. muricata var. semiglabra and S. muricata var. villosa.

Black roly-poly varieties

Var. muricata

Stems and leaves are hairless. Leaves are dark bluish-green, 6-20 mm long, 1-2 mm wide, and tapered at both ends.

Var. semiglabra

Stems have a covering of woolly hairs. Leaves are an elongated egg shape, 5-10 mm long. The upper surfaces are hairy and the lower surfaces slightly downy.

Var. villosa

The whole plant is softly hairy. Leaves are 6-20 mm long, 1-2 mm wide, and tapered at both ends.

Similar species

The hairiness of the villosa and semiglabra varieties of black roly-poly can cause them to be confused with galvanised burr (Sclerolaena birchii). However, the branches of black roly-poly are more tangled, the spines are longer and the plant is more spherical in appearance than galvanised burr. In general black roly-poly is darker green in colour, more hemispherical (half-sphere shaped) and tends to be less hairy than galvanised burr. 

Habitat

Black roly-poly is native to the temperate and semi-arid regions of New South Wales (NSW) and Queensland, growing primarily on clay and clay loam soils.

Acknowledgements

Author: Phillip Blackmore.

Technical reviewers: Stephen Johnson, Bob McGufficke, Birgitte Verbeek.

References

Auld, B.A. and Johnson, S.B. (2011) The biology of Australian Weeds 57. Sclerolaena birchii (F.Muell.) Domin. Plant Protection Quarterly 26 : 1, 2-7.

Auld, B.A., (1973). The effect of herbicides on the germination of galvanised burr (Bassia birchii). Australian Weeds Research Newsletter 18 : 22-3.

Auld, B.A., (1976). The biology of Bassia birchii (F.muell.). Weed Research 16 : 323-30.

Auld, B.A. And Martin, P.M., (1975). Morphology and distribution of Bassia birchii (F.Muell.). Proceedings of the Linnean Society of New South Wales 100 : 167-78.

Cunningham, G.M., Mulham, W.E., Milthorpe, P.L. And Leigh, J.H., (1981). Galvanised burr and Black roly-poly. Plants of Western New South Wales. P. 249. Soil Conservation Service of NSW and NSW Government Printing Office, Sydney.

Parsons, W. T. And Cuthbertson, E. G., (2001) Galvanised Burr and Five Spined Saltbush ,Noxious Weeds Of Australia Pp 379-83 CSIRO Publishing, Collingwood, Vic 3066, Australia.

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Control

Black roly-poly can be suppressed by a range of techniques, however a high level of control on grazing land is generally not economically justifiable.

The aim of a control program on grazing land should be to minimise the amount of seed entering the seed bank by reducing the numbers of large plants. This approach will reduce the occurrence and severity of future infestations.

Native Vegetation Act 2003

Clearing native species in New South Wales is regulated by the Native Vegetation Act 2003. Cultivation of land for crop establishment is regarded as clearing.

Clearing of galvanised burr and black roly poly may be permitted under the Native Vegetation Act 2003, subject to restrictions and requirements, for example, on land where galvanised burr has not been cleared in any systematic or conscientious manner, some clearing of galvanised burr as invasive native scrub may be permitted, provided the clearing improves or maintains environmental outcomes; or the clearing of any regrowth of galvanised burr may be permitted subject to time restrictions, i.e. after 10 years.

Seek advice regarding the restrictions and requirements associated with clearing black roly-poly from your Local Land Services.

Herbicide control

There are no herbicides registered to control black roly-poly, but plants can be grubbed from the ground and heaped for burning using a tractor-mounted blade. Seedlings will establish after the parent plants are removed and cultivation can then be used to control the populations of seedlings.

Cultivation

Seedlings are unlikely to establish from seed buried to a depth of 40 mm or more. Ploughing arable areas with an implement that inverts the soil will reduce the size of the viable seed bank in heavily infested areas.

Biocontrol

As part of a complex native ecosystem black roly-poly is attacked by several insects and diseases, however these organisms cannot suppress large numbers of plants.

Herbicide options

Contact your local council weeds officer for control advice for Black roly-poly (Sclerolaena muricata).

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Legal requirements

Black roly-poly (Sclerolaena muricata) is not declared in NSW under the Noxious Weeds Act 1993.

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Disclaimers

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 the NSW Office of Environment and Heritage for further details.

Reviewed 2014