Grader Grass (Themeda quadrivalvis)

Present distribution

Scientific name:	Themeda quadrivalvis (L.) Kuntze
Common name(s):	Grader Grass

This weed is not known to be naturalised in Victoria

Habitat:

Native to India & Nepal where it grows in grasslands receiving between 200 & 375mm annual rainfall, but thrives best in 500 to 875mm annual rainfall districts. Described as a weed in Australia, USA, New Caledonia, Fiji & Mauritius (Parsons & Cuthbertson 2001, Weeds Aust 2007). A weed of grasslands, disturbed areas, roadsides, railway embankments, moist sites, sugarcane, pasture, Lucerne & legume seed crops (Smith 2002, Kleinschmidt & Johnson 1977, Bishop 1981), ‘native woodlands’ (Calvert 1998) & Eucalypt open forest (Batianoff & Franks 1998). In QLD, distribution is mostly coastal, but is also spreading into drier areas posing a threat to grazing land in the drier tropics. In Ethiopia occurs in grassland containing ‘scrub trees’ to 2500 m [tropical] (Semple 1949). In Fiji a weed of roadsides & waste places (Smith 1979 in PIER 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; pasture dryland; pasture irrigation

Broad vegetation types
Coastal scrubs and grassland; coastal grassy woodland; grassland; plains grassy woodland; montane grassy woodland; riverine grassy woodland.

Colours indicate possibility of Themeda quadrivalvis infesting these areas.

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

map showing the potential distribution of grader grass

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

Impact

QUESTION	COMMENTS	RATING	CONFIDENCE
Social
1. Restrict human access?	Being a tall grass, growing to 2m in height and forming dense thickets (Calvert 1998, Weeds Aust 2007), it has the potential to impede individual access.	ML	M
2. Reduce tourism?	It is documented as a hazard on roadsides by reducing visibility on curves and corners (Parsons & Cuthbertson 2001), and although driving isn’t strictly classed as a ‘recreational activity’ it is likely to have a minor negative impact on driving ability. Additionally, its habit as a tall grass growing to 2m in height and forming dense thickets (Calvert 1998, Weeds Aust 2007) gives it the potential to negatively affect the aesthetics of an area.	ML	M
3. Injurious to people?	No information was found to suggest that T. quadrivalvis has any properties injurious to humans.	L	ML
4. Damage to cultural sites?	Due to the habit of this species as an annual grass it is likely to have little impact on cultural sites or infrastructure.	L	ML
Abiotic
5. Impact flow?	A terrestrial species, no impact on water flow.	L	M
6. Impact water quality?	A terrestrial species, no impact on water quality.	L	M
7. Increase soil erosion?	This species often already occurs in disturbed sites (Smith 2002), and combined with its capacity to grow in dense thickets, it is unlikely to cause an increase in soil movement.	L	ML
8. Reduce biomass?	The establishment of T. quadrivalvis may cause an increase in biomass due to its substantial height greater than many native grass species, including similar species Themeda australis, which it could replace in grassland situations. It also commonly grows in areas that are low in vegetation cover such as roadsides and railway embankments (Kleinschmidt & Johnson 1977).	L	ML
9. Change fire regime?	T. quadrivalvis increases fuel loads causing fires of an intensity that many native plants are not adapted to deal with and as a result thinning of native woodlands occur with each passing fire (Calvert 1998). Causes a fire hazard once the plant has matured and died (Bishop 1981), which being an annual is a regular occurrence. Likely to cause moderate increase in both frequency and intensity of fire.	MH	M
Community Habitat
10. Impact on composition (a) high value EVC	EVC= Montane grassy woodland (BCS= V); CMA= East Gippsland; Bioreg= Monaro tablelands; CLIMATE potential=L. Can occur in ‘native woodlands’ (Calvert 1998) and invade native grassland (Smith 2002) forming tall thickets covering large tracts of land, smothering native plants and greatly reducing diversity (Calvert 1998)’. Potential to cause a major displacement of some dominant species within the lower strata, however, due its lower climate match and small area of potential distribution in Victoria the impact of this species is likely to be reduced.	M	L
(b) medium value EVC	There are no medium value EVCs mapped within the potential distribution of T. quadrivalvis that are likely to be impacted on by this species.	L	M
(c) low value EVC	There are no low value EVCs mapped within the potential distribution of T. quadrivalvis that are likely to be impacted on by this species.	L	M
11. Impact on structure?	Can invade native grassland (Smith 2002) and form tall thickets covering large tracts of land, smothering native plants and greatly reducing diversity (Calvert 1998)’. Major effect on species in the lower layers (< 60%) of the floral strata.	MH	ML
12. Effect on threatened flora?	Can invade native grassland (Smith 2002) and form tall thickets covering large tracts of land, smothering native plants and greatly reducing diversity (Calvert 1998). However, no information specific to its impact on threatened flora was found documented, and due to the lower climate match of this species and very small area it could potentially occupy in Victoria it is likely to have a low impact.	M	ML
Fauna
13. Effect on threatened fauna?	No information was found documented regarding the effect of T. quadrivalvis on threatened fauna, though due to the lower climate match of this species and very small area it could potentially occupy in Victoria it is likely to have a minor impact.	ML	ML
14. Effect on non-threatened fauna?	Can invade native grassland (Smith 2002) and form tall thickets covering large tracts of land, smothering native plants and greatly reducing diversity (Calvert 1998). The ability of T. quadrivalvis to reduce flora diversity could impact on fauna that rely on certain native plant species for food or shelter, but due to the lower climate match of this species and very small area it could potentially occupy in Victoria it is likely to have a minor impact.	ML	ML
15. Benefits fauna?	Although, no information regarding its benefits to fauna were found documented, being a tall dense grass, similar to the native T. australis it is likely to provide some assistance in shelter and also as a food source to generalist grazers and seed eaters.	MH	ML
16. Injurious to fauna?	No information was found to suggest T. quadrivalvis has any properties that would be injurious to fauna.	L	M
Pest Animal
17. Food source to pests?	T. quadrivalvis is eaten by stock only in the short early stage of growth, after this time it is avoided. Horses have been observed consuming the mature ripe seed heads over winter (Bishop 1981). It is possible that the foliage or seeds of T. quadrivalvis could provide a source of food to minor pest animals, such as feral horses, however, its consumption by more serious pests, such as rabbits, was not found documented.	M	L
18. Provides harbor?	Being a tall grass, growing to 2m in height and forming dense thickets (Calvert 1998, Weeds Aust 2007), it has the potential to provide some benefit of harbour to pest species, however, no information was found documented.	M	L
Agriculture
19. Impact yield?	Documented as causing significant yield losses in sugar cane (Chapman 1969, Tilley 1969), however, sugarcane is not a crop grown in Victoria. It is also described as being a serious threat to productivity in pasture because of it’s ‘extremely short, barely useful life and its ability to spread quickly (Parsons & Cuthbertson 2001)’, however, it is stated that maintenance of a vigorous pasture will assist in preventing invasion (Pitt 1998). In addition, it also invades legume seed crops and Lucerne ‘and thereby causes financial losses (Calvert 1998, Parsons & Cuthbertson 2001)’. Yield impact, resulting in reduced productivity and financial loss are documented as an implication of invasion by T. quadrivalvis, but the level of impact is not clear from the information available.	M	L
20. Impact quality?	It is documented as a contaminant of crop and pasture seed and as a declared ‘restricted seed’ with a maximum of 500 seeds per kilogram allowed for commercial sale (Bishop 1981). More specifically it is described as a seed contaminant of Verano, a tropical pasture legume, and as a declared weed seed, it must be listed on the retail package label for sale (English & Hopkinson 1985). Seed contamination is likely to result in reduced agricultural quality, however, it is unknown if T. quadrivalvis would impact on similar crops growing in temperate climatic regions.	M	L
21. Affect land value?	T. quadrivalvis can be controlled under normal ‘good’ farm management practises (Bishop 1981) so it is unlikely to lead to a decrease in land value.	L	ML
22. Change land use?	It is described as one of the most ‘troublesome’ weeds in Verano, a legume seed crop, where removing weed seeds is described as ‘both time consuming and wasteful (English & Hopkinson 1985)’. Potential increased harvesting costs may deem it unviable to continue growing this crop, however no information was found specifically documented, and also whether it would impact on similar temperate seed crops.	M	L
23. Increase harvest costs?	It is documented as a contaminant of crop and pasture seed and as a declared ‘restricted seed’ with a maximum of 500 seeds per kilogram allowed for commercial sale (Bishop 1981). It is likely to cause an increase in harvest costs as it is described as one of the most ‘troublesome’ weeds in Verano seed, where having to remove weed seeds is described as ‘both time consuming and wasteful’ (English & Hopkinson 1985).	M	L
24. Disease host/vector?	Described as a host of Claviceps spp. the fungal pathogen that causes Ergot (Thomas et al 1945) in various grass species. Infection can render pasture grasses and cereal crops unsuitable for consumption by humans and stock because of the toxic effects of Ergot (Clarke 1999). However, due to the lower climate match of this species and very small area it could potentially occupy in Victoria it is likely to have a minor impact as a host.	M	L

Invasive

QUESTION	COMMENTS	RATING	CONFIDENCE
Establishment
1. Germination requirements?	Seeds germinate at anytime of the year when light and moisture are present (Parsons & Cuthbertson 2001).	H	M
2. Establishment requirements?	It appears that T. quadrivalvis can tolerate moderate shade, and Sillar (1969) found that mature seed was produced even in 75% shade. However, seedling establishment is documented to be inhibited by shade and where stands remain undisturbed seed germination is suppressed (Parsons & Cuthbertson 2001, Sillar 1969). It is therefore unclear from the available information to what extent shade impacts on ‘establishment’.	M	L
3. How much disturbance is required?	‘Can invade native grassland and seriously reduce diversity (Smith 2002)’. T. quadrivalvis is primarily a weed that establishes in disturbed sites such as roadsides, but it can also invade native grassland that is degraded to some degree (Parsons & Cuthbertson 2001). Can establish in minor disturbed natural ecosystems, e.g. grassland.	MH	M
Growth/Competitive
4. Life form?	Tall annual grass (Sillar 1969).	MH	H
5. Allelopathic properties?	Not allelopathic (PIER 2003). No evidence was found to suggest T. quadrivalvis possesses any allelopathic properties.	L	M
6. Tolerates herb pressure?	‘It is not harmful to stock but if other grasses are available it is left untouched (Kleinschmidt & Johnson 1977)’. Mature plants are unpalatable to stock and overgrazing of pasture grazing encourages grader grass to germinate and establish (Pitt 1998). Consumed but not preferred.	MH	M
7. Normal growth rate?	‘Growth is rapid when available moisture remains high, plants reaching a height of 2 metres in 6 to 8 weeks (Parsons & Cuthbertson 2001)’. There are not many native grass species that reach heights of 2m, therefore the documented rapid growth rate of T. quadrivalvis is likely to exceed that of most other species of the same life form, e.g. grasses.	H	M
8. Stress tolerance to frost, drought, w/logg, sal. etc?	Without fire or defoliation recruitment is greatly reduced, burning encourages germination of seeds (Sillar 1969). It is unlikely to be tolerant of frost due to its distribution in warmer areas. It is described as being able to withstand ‘quite dry conditions’ in parts of India (FAO 2004) and Australia, but is much more prevalent in areas of high rainfall (Parsons & Cuthbertson 2001) and its tolerance to drought was not found documented. Often found in moist areas, but its tolerance to water logging is not clear from the literature available. Its ability to tolerate salinity is also unknown. There was not enough information available to determine the overall stress tolerance of T. quadrivalvis.	M	L
Reproduction
9. Reproductive system	T. quadrivalvis is an annual grass and reproduces by seed (McIvor & Howden 2000). It is unclear from the information available what its pollination characteristics are, and whether it undertakes self-pollination and/or cross-pollination. The presumption must be made that it undertakes both forms of pollination so that its potential invasiveness is not underestimated.	ML	L
10. Number of propagules produced?	Described as being a prolific seeder (Parsons & Cuthbertson 2001) and as producing 633 000 seeds/kg (FAO 2004), however, the number of seeds produced by an individual plant was not found documented.	M	L
11. Propagule longevity?	Gardener et al (2001) found that no seed germinated after 2 years in a simulated soil seed bank. Seed viability is less than 5 years.	L	H
12. Reproductive period?	T. quadrivalvis is an annual grass (Sillar 1969) with each plant producing viable propagules for only 1 year. However, there is evidence to suggest that this species forms monocultures, with it described as forming, dense continuous stands on roadsides (Weeds Aust 2007) and tall thickets that cover large tracts of land smothering native plants (Calvert 1998). It is also documented that a large proportion of seed falls close to the parent plant (Parsons & Cuthbertson 2001). Potential to form self-sustaining monocultures.	H	M
13. Time to reproductive maturity?	‘Flowering begins 5 to 6 weeks after germination and ripe seeds are present at 10 weeks (Bishop 1981)’. Reaches maturity and produces viable propagules in under a year.	H	H
Dispersal
14. Number of mechanisms?	The majority of seeds fall close to the parent plant, however, seeds are also carried considerable distance on wool, fur, clothing and in soil moved by graders. Seed is also spread in mud sticking to animals and machinery and as a contaminant in agricultural produce, particularly pasture seed (Bishop 1981, Parsons & Cuthbertson 2001).	MH	MH
15. How far do they disperse?	It is documented that the majority of seeds fall close to the parent plant. However it is also described as having a prolific seeding habit with seeds being carried considerable distance on wool, fur, clothing and particularly by graders, slashers and other road vehicles (Bishop 1981, Burdekin 2005, Parsons & Cuthbertson 2001). Seed is also spread in mud sticking to animals and machinery and as a contaminant in agricultural produce. With its capacity to be dispersed by several mechanisms, particularly human and machinery dispersal, and because it is often found on roadsides, it is likely that at least one propagule will disperse greater than one kilometre.	H	M

References

Batianoff GN & Franks AJ 1998, ‘Weed invasion of the tropical Mackay coast, Queensland, Australia’, Plant Protection Quarterly, vol. 13, no. 3, pp. 123- 131.

Bishop HG 1981, ‘Grader grass-a nuisance weed’, Queensland Agricultural Journal, vol. 107, no. 5, pp. 235-239.

Burdekin Shire Council 2005, Leading the Burdekin Shire- Pest Management Plan, Burdekin Shire Council, Queensland.

Calvert G 1998, Weeds-The Silent Invaders, Australian Plants online, Association of Societies for Growing Australian Plants, viewed: 8/5/2007, http://farrer.csu.edu.au/ASGAP/APOL16/dec99-2.html

Chapman LS 1969, ‘Control of Habana oat grass’, Cane Growers quarterly Bulletin, vol. 33, pp. 8-10.

Clarke R 1999, ‘Ergot of pasture grasses’, Information Notes, Department of Primary Industries, Victoria, viewed: 14/5/2007, http://www.dpi.vic.gov.au/dpi/nreninf.nsf/Home+Page/DPI+InfoSeries~Home+Page?open

English BH & Hopkinson JM 1985, ‘Verano stylo seed production’, Queensland Agricultural Journal, vol. 111, no. 1, pp. 59-63.

Food and Agriculture Organisation of the United Nations (FAO) 2004, ‘Themeda quadrivalvis (L.) Kuntze’, viewed: 16/4/2007,
http://www.fao.org/ag/agP/AGPC/doc/GBASE/data/PF000331.HTM

Gardener CJ (The late), Whiteman LV & Jones RM 2001, ‘Patterns of seedling emergence over 5 years from the seed of 38 species placed on the soil surface under shade and full sunlight in the seasonally dry tropics’, Tropical Grasslands, vol. 35, pp. 218-225.

Kleinschmidt HE & Johnson RW 1977, Weeds of Queensland, S.R. Hampson, Government Printer, Queensland.

McIvor JG & Howden SM 2000, ‘Dormancy and germination characteristics of herbaceous species in the seasonally dry tropics of northern Australia’, Austral Ecology, vol. 25, pp. 213-222.

Parsons WT & Cuthbertson EG 2001, Noxious Weeds of Australia-Second Edition, CSIRO Publishing, Collingwood, Victoria.

Pacific Island Ecosystem at Risk (PIER) 2003, Risk Assessment Results: Themeda quadrivalvis, PIER, Hawaiian Ecosystems at Risk project, viewed: 16/4/2007, http://www.hear.org/Pier/wra/australia/thqua-wra.htm

Pacific Island Ecosystem at Risk (PIER) 2002, Pier Species Info: Themeda quadrivalvis, PIER, Hawaiian Ecosystems at Risk project, viewed: 16/4/2007, http://www.hear.org/Pier/species/themeda_quadrivalvis.htm

Pitt JL 1998, ‘Grader Grass’, Agnote, vol. 499, no. F9, Agdex No: 647, pp. 1-3.

Semple AT 1949, ‘Some grass species of Ethiopia’, Grass & Forage Science, vol. 4, no. 2, pp 105-110.

Sillar DI 1969, ‘Control of Grader Grass (Themeda quadrivalvis)’, vol. 26, pp. 581-586.

Smith AC 1979, Flora Vitiensis nova: a new flora of Fiji. National Tropical Botanical Garden, Lawai, Kauai, Hawaii. Volume 1.

Smith NM 2002, Weeds of the wet/dry tropics of Australia-a field guide. Environment Centre NT, Inc.

Thomas KM, Ramakrishnan TS & Srinivasan KV 1945, ‘The natural occurrence of ergot in South India’, Proc. Indian Acad. Sci. vol. 21, pp. 93-100.

Tilley LGW 1969, ‘Mossman growers beware! A new grass pest’, Cane Growers Quarterly Bulletin, vol. 32, no. 3, pp. 76-7.

Weeds Australia (Weeds Aust) 2006, Weed Identification-Grader Grass, National Weeds Strategy, Australian Weeds Committee, viewed: 16/4/2007, http://www.weeds.org.au/

Global present distribution data references

Australian National Herbarium (ANH) 2007, Australia’s Virtual Herbarium, Australian National Herbarium, Centre for Plant Diversity and Research, viewed: 2/5/2007, http://www.anbg.gov.au/avh/

Global Biodiversity Information Facility (GBIF) 2007, Global biodiversity information facility: Prototype data portal, viewed; 2/5/2007, http://newportal.gbif.org/welcome.htm

Semple AT 1949, ‘Some grass species of Ethiopia’, Grass & Forage Science, vol. 4, no. 2, pp 105-110.

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