Spiny burrgrass (Cenchrus incertus)

Present distribution

Scientific name:	Cenchrus incertus M. Curtis
Common name(s):	spiny burrgrass

Map showing the present distribution of this weed.

Habitat:

Native to North and Central America, but also weedy in parts of its native range. Has become a weed in South Africa, South America and some Mediterranean countries. Also naturalised Vic, SA and in Qld, NT and WA (Parsons & Cuthbertson, 2001). Aggressively colonizes open, disturbed sites in fields, orchards, vineyards, alfalfa, cultivated crops, ditch banks. Often infests sandy, well-drained soils, (CDFA, 2007) but also grows on heavier soils; also roadsides, neglected areas and occasionally lawns, dry and irrigated farmland (Parsons & Cuthbertson, 2001). Found in open scrub and scrub woodland, beside salt ponds and in dense, low, coastal forest (GBIF, 2007); semi-natural grassland (Szigetvari, 2002); sea shores and sand dunes (Phillips & Chen, 2006).

Potential distribution

Potential distribution produced from CLIMATE modelling refined by applying suitable landuse and vegetation type overlays with CMA boundaries

Map Overlays Used

Land Use:
Broadacre cropping; forest private plantation; forest public plantation; horticulture; pasture dryland; pasture irrigation

Broad vegetation types
Coastal scrubs and grassland; coastal grassy woodland; heathy woodland; lowland forest; heath; grassland; plains grassy woodland; riverine grassy woodland; rainshadow woodland; mallee; mallee heath; boinka-raak; mallee woodland; wimmera / mallee woodland

Colours indicate possibility of Cenchrus incertus infesting these areas.

In the non-coloured areas the plant is unlikely to establish as the climate, soil or landuse is not presently suitable.

Red= Very high	Orange = Medium
Yellow = High	Green = Likely

Impact

QUESTION	COMMENTS	RATING	CONFIDENCE
Social
1. Restrict human access?	“An erect or spreading annual grass to 60 cm high. Inflorescence a spike-like panicle consisting of up to 40 burrs; spines sharply pointed, finely barbed, rigid to 7 mm long.” Causes “inconvenience and discomfort to workers in irrigated crops” when burrs are present (December to April) (Parsons & Cuthbertson, 2001). High nuisance value during this time of year.	MH	MH
2. Reduce tourism?	Some recreational activities may be affected; burrs remain on the ground for several months after the plant dies Barnard, T. (pers. comms.).	MH	M
3. Injurious to people?	“Spines can easily puncture the skin of animals.” Causes “inconvenience and discomfort to workers in irrigated crops” (Parsons & Cuthbertson, 2001), and can remain on the ground for several months after the plant dies Barnard, T. (pers. comms.). Burrs can cause injury for most of the year.	MH	MH
4. Damage to cultural sites?	As a grass to 60cm that is difficult to identify until it is flowering (Parsons & Cuthbertson, 2001), it would have little effect on visual aesthetics or structure of cultural sites.	L	MH
Abiotic
5. Impact flow?	Terrestrial species (Parsons & Cuthbertson, 2001).	L	MH
6. Impact water quality?	Terrestrial species (Parsons & Cuthbertson, 2001).	L	MH
7. Increase soil erosion?	This species can be annual or perennial (Parsons & Cuthbertson, 2001). As an annual, it may cause some increase in erosion, however, as it usually invades “disturbed road edges and infests neglected areas and summer crops” (Parsons & Cuthbertson, 2001), it is unlikely to displace many soil-binding perennial species. Low probability of large-scale soil movement.	L	MH
8. Reduce biomass?	Can be an annual or perennial, but tends to grow in open, neglected and disturbed areas (Parsons & Cuthbertson, 2001; CDFA, 2007). May increase biomass of previously sparsely vegetated areas.	L	MH
9. Change fire regime?	“Spiny burr-grass forms tussocks up to 60 cm and more across. Most plants die in autumn or early winter” (Parsons & Cuhbertson, 2001). In dense patches the plant may increase the frequency of fire risk somewhat.	ML	MH
Community Habitat
10. Impact on composition (a) high value EVC	EVC=Box Ironbark Forest (V); CMA=North East; Bioreg=Northern Inland Slopes; VH CLIMATE potential. “Spiny burr-grass, which occupies open dry sandy situations…is a pioneer plant of disturbed sandy soils” and “does not establish readily in pastures” (Parsons & Cuthbertson, 2001). Whilst it can “develop into dense infestations in favourable conditions” (Mullen, 2005), these conditions are likely to be highly disturbed, so it is unlikely to invade intact vegetation to a significant degree. Very little displacement of any indigenous species.	L	MH
(b) medium value EVC	EVC=Lowland Grassy Forest (D); CMA=East Gippland; Bioreg=East Gippsland Lowland; VH CLIMATE potential. “Spiny burr-grass, which occupies open dry sandy situations…is a pioneer plant of disturbed sandy soils” and “does not establish readily in pastures” (Parsons & Cuthbertson, 2001). Unlikely to invade intact vegetation to a significant degree. Very little displacement of any indigenous species.	L	MH
(c) low value EVC	EVC=Lowland Forest (LC); CMA=East Gippsland; Bioreg=East Gippsland Lowlands; VH CLIMATE potential. “Spiny burr-grass, which occupies open dry sandy situations…is a pioneer plant of disturbed sandy soils” and “does not establish readily in pastures” (Parsons & Cuthbertson, 2001). Whilst it can “develop into dense infestations in favourable conditions” (Mullen, 2005), these conditions are likely to be highly disturbed, so it is unlikely to invade intact vegetation to a significant degree. Very little displacement of any indigenous species.	L	MH
11. Impact on structure?	“Spiny burr-grass, which occupies open dry sandy situations…is a pioneer plant of disturbed sandy soils” and “does not establish readily in pastures” (Parsons & Cuthbertson, 2001). Whilst it can “develop into dense infestations in favourable conditions” (Mullen, 2005), these conditions are likely to be highly disturbed, so it is unlikely to invade intact vegetation to a significant degree. Minor effect on the lower stratum only.	L	MH
12. Effect on threatened flora?	No evidence found.	MH	L
Fauna
13. Effect on threatened fauna?	“Spiny burr-grass, which occupies open dry sandy situations and is a pioneer plant of disturbed sandy soils, also grows well under irrigation” (Parsons & Cuthbertson, 2001). Unlikely to occupy habitat for threatened fauna.	L	MH
14. Effect on non-threatened fauna?	Spiny burrgrass tends to grow in areas that are unlikely to be crucial to the survival of fauna species. Without the burrs, it “could have some value as a pasture species in semi-arid areas (Parsons & Cuthbertson, 2001). Might even provide a food source prior to burr formation in summer.	L	MH
15. Benefits fauna?	Without the burrs, it “could have some value as a pasture species in semi-arid areas (Parsons & Cuthbertson, 2001). May provide a food source for grazing fauna when burrs are not present.	MH	MH
16. Injurious to fauna?	“Spines can easily puncture the skin of animals” and burrs “cause ulcers in the mouths of grazing animals” from December to April (Parsons & Cuthbertson, 2001). Potential to injure fauna when burrs present.	MH	MH
Pest Animal
17. Food source to pests?	Without the burrs, it “could have some value as a pasture species in semi-arid areas (Parsons & Cuthbertson, 2001). May provide a food source for grazing pests when burrs are not present. Minimal food source.	L	MH
18. Provides harbour?	“Spiny burr-grass forms tussocks up to 60 cm and more across. Most plants die in autumn or early winter” (Parsons & Cuhbertson, 2001). May provide harbour for some minor pests for part of the year.	ML	MH
Agriculture
19. Impact yield?	“Spiny burr-grass does not establish readily in pastures.” Although it does occur in summer crops, it is not documented to affect the yield, and does not compete well with crops, such as lucerne, nor in highly fertile soil (Parsons & Cuthbertson, 2001).	L	MH
20. Impact quality?	“The burrs become badly tangled in wool, lowering its value. Spines easily puncture the skin of animals thus affecting the value of the hides.” It occurs as a contaminant in dried fruit and may infest lucerne hay (Parsons & Cuthbertson, 2001). Major impact on quality across a range of products.	MH	MH
21. Affect land value?	Not known to affect land values.	L	M
22. Change land use?	Infestations can be controlled using a number of different techniques depending upon agricultural activities. Such techniques are: early cultivation; heavy grazing with sheep; establishing strong pasture growth particularly lucerne (Parsons & Cuthbertson, 2001). Some temporary change may be necessary depending upon density of infestation and agricultural activity. Not likely to downgrade use permanently, however.	ML	MH
23. Increase harvest costs?	Burrs in wool, “make sheep difficult to handle, which results in penalty rates being paid to shearers. Penalty rates are also paid to abattoirs staff handling burr-infested sheep” (Parsons & Cuthbertson, 2001). Increase in harvest costs minor, as extra time is not required, but extra incentive is.	M	MH
24. Disease host/vector?	None evident in a literature that focuses on agricultural impacts eg. Parsons & Cuthbertson (2001.	L	MH

Invasive

QUESTION	COMMENTS	RATING	CONFIDENCE
Establishment
1. Germination requirements?	Some germination occurs at any time of the year except mid-winter (Parsons & Cuthbertson, 2001). Requires seasonal temperatures.	MH	MH
2. Establishment requirements?	Light may inhibit germination, but this seems to be overcome by burial in soil, rather than canopy cover, as spiny burrgrass tends to grow in open, neglected and disturbed areas, with poor establishment in well-maintained pasture (Parsons & Cuthbertson, 2001; CDFA, 2007). Requires access to open ground for good establishment, but can grow under some canopy cover.	MH	MH
3. How much disturbance is required?	Aggressively colonises open, disturbed sites in fields, orchards, vineyards, alfalfa, cultivated crops, ditch banks. Often infests sandy, well-drained soils. (CDFA, 2007); also roadsides, neglected areas and occasionally lawns (Parsons & Cuthbertson, 2001). Establishes in highly disturbed natural ecosystems.	ML	MH
Growth/Competitive
4. Life form?	Annual, occasionally perennial, grass (Parsons & Cuthbertson, 2001).	MH	MH
5. Allelopathic properties?	None noted in Parsons & Cuthbertson (2001) which usually includes this information.	L	M
6. Tolerates herb pressure?	Recorded as unpalatable (McKinney & Fowler, 1991), however, burrs “cause ulcers in the mouths of grazing animals” (Parsons & Cuthbertson, 2001), so grazing does seem to occur. Heavy grazing is a control measure to prevent seeding (Parsons & Cuthbertson, 2001), but seed production is likely to occur under moderate grazing.	MH	MH
7. Normal growth rate?	Lucerne and Rhodes grass (perennial pasture) compete well with spiny burrgrass and it “doesn’t establish readily in pasture.” Growth rate can be rapid (Parsons & Cuthbertson, 2001). Growth rate equal to similar life forms.	M	MH
8. Stress tolerance to frost, drought, w/logg, sal. etc?	“Fire is an effective control technique when conducted prior to seed set” (CDFA, 2007). Recorded on beaches and on the edge of salt ponds and meadows (GBIF, 2007). Grows on well-drained sand in semi-arid regions. “Most plants die in autumn or early winter” and require a mild winter if they are to survive at all (Parsons & Cuthbertson, 2001). Not tolerant of fire. Not tolerant of waterlogging. May have some tolerance to frost, but not very cold temperatures. Will tolerate drought, but not arid conditions. High tolerance of salinity. Not tolerant of two stresses, some tolerance of one, and high tolerance of two.	MH	MH
Reproduction
9. Reproductive system	Reproduce by seed. Roots are formed at basal nodes if in contact with soil (Parsons & Cuthbertson, 2001), but this is not noted as a reproductive method. Self-compatible (McKinney & Fowler, 1991). May also be able to outcross, but no information found.	ML	L
10. Number of propagules produced?	Up to 1000 seeds produced per plant (Parsons & Cuthbertson, 2001).	ML	MH
11. Propagule longevity?	Dormant up to 3 years (Parsons & Cuthbertson, 2001).	L	MH
12. Reproductive period?	Spiny burrgrass can grow as a perennial, “regrowing from a crown each spring” (Parsons & Cuthbertson, 2001). Short-lived (Hall et al, 2006). Likely to produce viable propagules for only 1-2 years, but may be slightly longer.	M	M
13. Time to reproductive maturity?	Germinates in spring or summer with burrs (seed) produced from December to April (Parsons & Cuthbertson, 2001). Reaches reproductive maturity in less than one year.	H	MH
Dispersal
14. Number of mechanisms?	Burrs attach to wool, fur and clothing; also transported by water in irrigation areas (Parsons & Cuthbertson, 2001). Propagules spread by attachment and water.	MH	MH
15. How far do they disperse?	This weed “grows well on disturbed rad edges from where burrs readily attach to vehicle tyres” also a hay contaminant and found in dried fruit transported from the mainland to Tasmania (Parsons & Cuthbertson, 2001). Very likely that propagules will be dispersed greater than 1km on a regular basis.	H	MH

References

Barnard, T. (pers. comm.) Catchment Management Officer, Wodonga. Tel (02) 6043 7951. 01/05/03

California Department of Food and Agriculture (CDFA) 2007, Encyclooweedia, viewed:21/2/2007, www.cdfa.ca.gov/phpps/ipc/weedinfo/cenchrus.htm

Global Biodiversity Information Facility (GBIF) 2007, Global biodiversity information facility: Prototype data portal, viewed 21/02/2007, http://www.gbif.org/

Hall, D.W. Vandiver, V.V. & Ferrell, J.A. 2006, Coast Sandspur (Field Sandbur), Cenchrus incertus Curtis, University of Florida IFAS Extension, viewed:21/02/2007, http://edis.ifas.ufl.edu/FW010

McKinney K.K & Fowler, N.L. 1991, ‘Genetic adaptations to grazing and mowing in the unpalatable grass Cenchrus incertus,’ Oecologia, vol. 88(2), pp. 238-242.

Mullen, C.L. 2005, ‘Spiny burrgrass,’ Agfact P7.6.21, 3rd ed., NSW Department of Primary Industries, Orange, www.agric.nsw.gov.au/reader/weed-list/spiny-burrgrass.pdf

Parsons, W.T. & Cuthbertson, E.G. 2001, Noxious weeds of Australia, 2nd ed., CSIRO Publishing, Collingwood.

Global present distribution data references

Australian National Herbarium (ANH) 2006, Australia’s Virtual Herbarium, Australian National Herbarium, Centre for Plant Diversity and Research, viewed 26/9/2006, http://www.anbg.gov.au/avh/

Consortium of California Herbaria Participants, 2007, ‘Accession Results,’ The University and Jepson Herbaria, University of California, Berkeley, viewed: 22/02/2007, http://ucjeps.berkeley.edu/interchange.html.

Da Silva, I & Da silva, A. 2004, ‘A preliminary checklist of the vascular plants of Mozambique,’ Southern African biotanical Diversity Network Report No. 30, BABONET,
Pretoria, www.sabonet.org.za/downloads/30_mozambique_vascular/mozambique_vascular_plants.pdf

Global Biodiversity Information Facility (GBIF) 2007, Global biodiversity information facility: Prototype data portal, viewed 21/02/2007, http://www.gbif.org/

Jepson Manual

Missouri Botanical Gardens (MBG) 2006, w3TROPICOS, Missouri Botanical Gardens Database, viewed: 26/11/2006, http://mobot.mobot.org/W3T/Search/vast.html

Phillips, S.M. & Chen, S. 2006, ‘Cenchrus,’ in Flora of China Editorial Committee, 2006, Flora of China, eFloras, viewed: 22/02/2007, www.efloras.org

Szigetvari, C. 2002, ‘Distribution and phytoscociological relations of two introduced plant species in an open sand grassland area in the Great Hungarian Plain,’ Acta
Botanica Hungarica, vol. 44, pp. 163-183.

Western Australian Herbarium (WAH) 2006, Euphorbia terracina, FloraBase — The Western Australian Flora. Department of Environment and Conservation. Viewed: 2/1/2007, http://florabase.calm.wa.gov.au/

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