Giant Parramatta grass (Sporobolus fertilis)

Giant Parramatta grass is a tall, aggressive perennial grass. Common in coastal areas of NSW and Qld.

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How does this weed affect you?

Giant Parramatta grass can dramatically decrease economic viability of grazing land and lower land values. It invades pastures and replaces more productive types of grass, especially after overgrazing or soil disturbance. 

Where is it found?

Giant Parramatta grass is native to tropical Asia and the Malesia region. Current distribution in Australia is from northern Cape York to the southern coast of New South Wales, with isolated infestations in Victoria and the Northern Territory.

Maps and records

• Recorded presence of Giant Parramatta grass during property inspections (Map: Biosecurity Information System - Weeds, 2017-2023)
  These records are made by authorised officers during property inspections under the Biosecurity Act 2015. Officers record the presence of priority weeds in their council area and provide this to the NSW Department of Primary Industries. Records reflect the presence of the weed on the date of inspection.
  
  

How does it spread?

Giant Parramatta grass produce a large amount of seed that is dispersed by water, wind and machinery. At maturity seeds become sticky and can attach to hair or fur. Plants are capable of producing 85,000 seeds per square metre.

What does it look like?

Giant Parramatta grass is a coarse tussocky grass, 70-160 cm in height. The seed head is up to 40 cm long and 1-2 cm wide. Stems grow in a fan-like arrangement and the leaf-sheaths are folded. Leaf blades are up to 50 cm long and 1.5–5 mm wide. Its flower head is a dark, slaty green, dense, spike-like panicle 25-45 cm long, with branches usually lax at maturity, and sometimes diverging slightly. The spikelets are 1.5-2 mm long.

Acknowledgements

www.northcoastweeds.org.au

Authors: David Officer

Editing: Elissa van Oosterhout

Technical review: Rod Ensbey, Tony Cook, Birgitte Verbeek, Sethu Ramasamy

References

NSW Department of Primary Industries (2012) Primefact 1239 - Nigrospora crown rot for biocontrol of giant Parramatta grass

More information

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Control

Biological control

Recent research into a naturally occurring (endemic) fungus Nigrospora oryzae has shown it to cause crown rot in weedy Sporobolus grasses, particularly giant Parramatta grass. As land managers are becoming aware of Nigrospora crown rot and integrating it with their existing management strategies, they are finding that chemical control is becoming less necessary for longterm suppression of giant Parramatta grass. Nigrospora crown rot disease has been found from the Tweed to the lower mid-north coast in NSW. 

Nigrospora crown rot fungus

Nigrospora crown rot fungus is generally a saprophyte (uses dead plant material for nutrients) and is occasionally a secondary cause of disease in plants. Recent research suggests that the fungus works in combination with another endophyte fungus speces (most likely Fusarium species) to cause the crown rot disease in giant Parramatta grass. Crown rot disease is known to kill giant Parramatta grass and reduce infestations to non-economic levels over a couple of years. Up to 78% reduction in tussock size (over 15 months) and 64% reduction in tussock presence (over 12 months) has been observed in the field, due to the effects of Nigrospora crown rot. 

Nigrospora crown rot symptoms

The crown rot produces pale orange leaves on diseased tillers. The diseased tillers are easy to remove from the crown and have a brown-coloured base instead of the normal white colour. Yellowing caused by crown rot will always occur in the central folded leaf of a tiller, not just in the outer leaves as can be caused by frost or age. The symptoms first become obvious in spring 7-10 days after the first substantial rain after winter. Diseased plants are then easiest to spot from late December to mid January. During autumn and winter the symptoms of the disease tend to disappear, reappearing the following spring. 

Using Nigrospora as a biocontrol agent

Nigrospora fungus may need to be introduced to an infestation and managed for maximum effect, or it may already be present in small amounts and only require better management to increase its spread and effectiveness. 

Spores can be introduced by transplanting diseased plants. Diseased plants can be introduced from other areas, but it is best practice to source infected plants from local infestations whenever possible. It is worth making an initial check for crown rot-affected plants that may have gone unnoticed, before introducing diseased plants from outside the local area. The natural spread of the disease has been patchy, but with more producers introducing diseased plants this will improve. Contact your local weeds officer who may be able to recommend sites with active crown rot disease infections.

Diseased plants should be transplanted along ridges and areas of high cattle traffic, and also in areas where soils have better water holding capacity to minimise the likelihood that plants will not perish from dry conditions. Dig up diseased plants using a mattock or spade and take 5-10 cm of soil and roots. Keep the plants cool between digging up and planting. Try to plant when the soil is moist. Use a mattock to open the soil next to a healthy WSG plant. Plant the diseased plant in the hole and stomp around it to ensure good root ball-to-soil contact. The best time to introduce diseased plants is between late spring and early autumn. Diseased plants are hard to find in late autumn and winter and plant transfer is not recommended at that time of year. 

Once introduced, spores can be spread through an infestation in a number of ways:

• in water with overland flows after rain
• in air, short distances to new host plants, and
• through animal and vehicle movement.

Over time rain water will move spores downhill. By planting diseased plants into an infestation at the top of a ridge or hill, rain water will spread the spores through an infestation. A single diseased plant can spread spores and infect plants over 0.1 ha in 12 months. Spores from diseased plants can move in the air a short distance to new host plants. Disease incidence is often highest along cattle tracks and is more likely to show up in areas where cattle movements are more frequent. It is also likely that vehicles aid the movement of spores. Slashers and other cutting equipment are also likely to move diseased plant material around a property.

Restrictions on the movement of diseased plants

Giant Parramatta grass is a declared plant in NSW and movement of plants may require a permit. Check with your local council weeds officer before moving plants. It is best practice to identify and use any local infection sites for diseased plant transfers.

Managing crown rot for maximum control

Crown rot can be managed for maximum suppression and control. Initial research has observed a greater rate of disease spread in infestations that are well grazed. Moderate to heavy grazing produces a flush of new growth. Disease symptoms occur in new shoots while they are still short and green, and do not occur in tall, hayed-off plants. Any management practice that produces a flush of new growth is more likely to help the spread and effectiveness of disease. Crown rot symptoms have also been seen on new growth resulting from burning and slashing, and further research is investigating these approaches. 

Effects on native Sporobolus species

Native Sporobolus grasses are not usually present in high densities in pastures as they lack the competitive ability of the introduced weedy Sporobolus grasses. There have been no observations of Nigrospora crown rot in any native species in the field. Host specificity testing with the natives Sporobolus creber and Sporobolus diandrus has shown no evidence of crown rot symptoms. N. oryzae will grow on the native Sporobolus virginicus but no evidence of disease has been seen. Because Sporobolus virginicus is an important plant for maintaining the stability of sandy coastal areas, more research is needed to confirm its level of susceptibility to Nigrospora crown rot. The geographic separation between Sporobolus virginicus and other weedy Sporobolus grasses may minimise the transfer of N. oryzae to this important native species. 

Chemical control

There are a number of herbicides registered for the control of giant Parramatta grass.

Herbicide options

See Using herbicides for more information.

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PERMIT 9792 Expires 30/11/2025
Glyphosate 360 g/L (Various products)
Rate: 3.3 L per 10 L of water
Comments: Wick wiper application. Apply when plant is actively growing.
Withholding period: Nil.
Herbicide group: 9 (previously group M), Inhibition of 5-enolpyruvyl shikimate-3 phosphate synthase (EPSP inhibition)
Resistance risk: Moderate

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2,2-DPA 740 g/kg (Various products)
Rate: 1.0 kg per 100 L of water
Comments: Handgun application.
Withholding period: 7 days for harvest; 2 days for grazing/foraging
Herbicide group: 15 (previously group J), Inhibition of very long chain fatty acid synthesis (VLCFA inhibitors)
Resistance risk: Moderate

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2,2-DPA 740 g/kg (Various products)
Rate: 5–10 kg/ha
Comments: Boom spray application. Apply when plants are actively growing.
Withholding period: 7 days for harvest; 2 days for grazing/foraging
Herbicide group: 15 (previously group J), Inhibition of very long chain fatty acid synthesis (VLCFA inhibitors)
Resistance risk: Moderate

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Flupropanate 745 g/L (Tussock®)
Rate: 200 mL per 100 L of water
Comments: High volume spot spray. Best results during late winter and early spring when desirable species are semi-dormant. Observe 4 month withholding period for blanket spray application.
Withholding period: Spot spray: Do NOT graze or cut for stock feed for at least 14 days. Blanket spray: Do NOT graze, or cut for stock feed for at least 4 months. If stock are grazed in treated areas after required time has passed, remove stock from treated areas and do NOT slaughter or milk for human consumption until they have been on clean feed for at least 14 days.
Herbicide group: 15 (previously group J), Inhibition of very long chain fatty acid synthesis (VLCFA inhibitors)
Resistance risk: Moderate

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Flupropanate 745 g/L (Tussock®)
Rate: 1.5–2.0 L/ha
Comments: Boom spray. Best results during late winter and early spring when desirable species are semi-dormant. Observe 4 month withholding period for blanket spray application.
Withholding period: Spot spray: Do NOT graze or cut for stock feed for at least 14 days. Blanket spray: Do NOT graze, or cut for stock feed for at least 4 months. If stock are grazed in treated areas after required time has passed, remove stock from treated areas and do NOT slaughter or milk for human consumption until they have been on clean feed for at least 14 days.
Herbicide group: 15 (previously group J), Inhibition of very long chain fatty acid synthesis (VLCFA inhibitors)
Resistance risk: Moderate

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Flupropanate 86.9 g/kg (GP Flupropanate)
Rate: 15 kg /ha
Comments: Apply when the pasture is dormant or semi-dormant. Optimum application time is autumn and early spring. Do not apply in severe droughts or to weeds retarded by burning.
Withholding period: Do not graze or cut for stock feed areas which have received any treatment other than spot treatment for at least 4 months. Spot treatment: Do not graze or cut for stock feed for at least 14 days. If stock are grazed in treated areas after required time has passed, remove stock from treated areas and do NOT slaughter or milk for human consumption until they have been on clean feed for at least 14 days. This requirement applies permanently to treated areas.
Herbicide group: 15 (previously group J), Inhibition of very long chain fatty acid synthesis (VLCFA inhibitors)
Resistance risk: Moderate

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Flupropanate 86.9 g/kg (GP Flupropanate)
Rate: 1.5 g/m2
Comments: Spot application apply all year round.
Withholding period: Do not graze or cut for stock feed areas which have received any treatment other than spot treatment for at least 4 months. Spot treatment: Do not graze or cut for stock feed for at least 14 days. If stock are grazed in treated areas after required time has passed, remove stock from treated areas and do NOT slaughter or milk for human consumption until they have been on clean feed for at least 14 days. This requirement applies permanently to treated areas.
Herbicide group: 15 (previously group J), Inhibition of very long chain fatty acid synthesis (VLCFA inhibitors)
Resistance risk: Moderate

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Glyphosate 360 g/L (Various products)
Rate: 10–15 mL per 1 L of water
Comments: Spot spray. Apply when plants are actively growing.
Withholding period: Nil.
Herbicide group: 9 (previously group M), Inhibition of 5-enolpyruvyl shikimate-3 phosphate synthase (EPSP inhibition)
Resistance risk: Moderate

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Glyphosate 360 g/L (Various products)
Rate: 6.0 L/ha
Comments: Boom application for pasture replacement/improvement and best done as a split treatment.
Withholding period: Nil.
Herbicide group: 9 (previously group M), Inhibition of 5-enolpyruvyl shikimate-3 phosphate synthase (EPSP inhibition)
Resistance risk: Moderate

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Biosecurity duty

The content provided here is for information purposes only and is taken from the Biosecurity Act 2015 and its subordinate legislation, and the Regional Strategic Weed Management Plans (published by each Local Land Services region in NSW). It describes the state and regional priorities for weeds in New South Wales, Australia.

Area	Duty
All of NSW	General Biosecurity Duty All pest plants are regulated with a general biosecurity duty to prevent, eliminate or minimise any biosecurity risk they may pose. Any person who deals with any plant, who knows (or ought to know) of any biosecurity risk, has a duty to ensure the risk is prevented, eliminated or minimised, so far as is reasonably practicable.
Central Tablelands	Regional Recommended Measure* (for Regional Priority - Eradication) Land managers should mitigate the risk of the plant being introduced to their land. Land managers should eradicate the plant from the land and keep the land free of the plant. A person should not deal with the plant, where dealings include but are not limited to buying, selling, growing, moving, carrying or releasing the plant. Notify local control authority if found.
Hunter	Regional Recommended Measure* (for Regional Priority - Asset Protection) Land managers should mitigate the risk of the plant being introduced to their land. Land managers should mitigate spread of the plant from their land. A person should not buy, sell, move, carry or release the plant into the environment. Land managers should reduce the impact of the plant on assets of high economic, environmental and/or social value.
North West An exclusion zone is established for all lands in the region, except the core infestation area comprising the: Tamworth Regional Council.	Regional Recommended Measure* (for Regional Priority - Containment) Whole of region: Land managers mitigate the risk of new weeds being introduced to their land. Within exclusion zone: Land managers should eradicate the plant from the land and keep the land free of the plant. A person should not deal with the plant, where dealings include but are not limited to buying, selling, growing, moving, carrying or releasing the plant. Notify local control authority if found. Within core infestation: Land managers should mitigate spread of the plant from their land. A person should not buy, sell, move, carry or release the plant into the environment. Land managers should reduce the impact of the plant on assets of high economic, environmental and/or social value.
	*To see the Regional Strategic Weeds Management Plans containing demonstrated outcomes that fulfil the general biosecurity duty for this weed click here

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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 Biodiversity Conservation Act 2016 and Local Land Services Amendment Act 2016 restrict some pasture improvement practices where existing pasture contains native species. Contact Local Land Services for further details.

Reviewed 2023