Pasture dieback

Updated: June 2020

Latest Webinar Update

NSW DPI recently hosted a webinar on pasture dieback: 'Responding to the on-farm challenges of pasture dieback'. Links to the presentation recordings can be found below:

About pasture dieback

Pasture dieback is a condition that kills sown and native summer growing pastures. It starts as small patches and can spread to affect large areas. The grasses die allowing broadleaf weeds to colonise. Often groundcover in these areas is low. Pasture dieback is not limited by landscape or soil type. Livestock avoid grazing affected areas making them unproductive (Figure 1).

Pasture dieback was first identified in Central Queensland. It has now spread across Queensland in coastal and inland regions from the Atherton Tablelands to south-west of Brisbane. Suspected pasture dieback was reported on a property in northern NSW in autumn 2019. Following good rainfall in autumn 2020, pasture dieback was confirmed on the North Coast of NSW.


Pasture dieback

What to look for

Symptoms are most evident when pastures are actively growing during spring, summer and autumn, especially following significant rainfall. Symptoms of pasture dieback include:

  • Yellowing, reddening and purpling of leaves. Discolouration can vary between species. Starts with the oldest leaves and typically begins at the leaf tip and moves along the leaf blade towards the stem (Figure 2).
  • Infected plants become stunted and unthrifty. Plants have fewer leaves and tillers, smaller seed heads and a smaller root system.
  • Starts as small patches, less than 1 m2. Patches grow and merge and affect large areas.
  • Rapid increase in size of the infected area following significant rainfall in spring-autumn.
  • Eventually the affected plants die.
  • Patches where grasses have been killed are colonised by broadleaf weeds and legumes.

Many of the dieback plant symptoms can be caused by a range of other factors. Including: mineral deficiency, moisture stress, cold temperatures, herbicide damage, water logging and nematodes. It is important to eliminate these before assuming dieback. However a combination of symptoms, including a rapid increase of the affected area following significant rainfall are good indicators of pasture dieback.


yellowing and reddening of leaves on plant

Species affected

Pasture dieback affects summer growing grasses. All of the commonly sown summer growing grasses are susceptible as well as a number of native and naturalised grasses. It has not been reported in temperate grasses, with the exception of a single case of an annual ryegrass forage crop.

Species known to be affected include:

  • Bahia Grass (Paspalum notatum)
  • Black spear-grass (Heteropogon contortus)
  • Bambatsi panic (Panicum coloratum)
  • Buffel grass (Cenchrus ciliaris)
  • Carpet grass (Axonopus compressus)
  • Couch (Cynodon dactylon)
  • Creeping bluegrass (Bothriochloa insculpta)
  • Digit grass (Digitaria eriantha)
  • Forest bluegrass (Bothriochloa bladhii ssp. glabra)
  • Gatton and green panic (Panicum maximum)
  • Golden beard grass (Chrysopogon fallax)
  • Kikuyu (Pennisetum clandestinum)
  • Para grass (Brachiaria mutica syn. Urochloa mutica)
  • Paspalum (Paspalum dilatatum, P. mandiocanum (syn. P. wettsteinii), P. urvillei and P. plicatulum)
  • Purple pigeon grass (Setaria incrassata)
  • Rhodes grass (Chloris gayana)
  • Sabi grass (Urochloa mosambicensis)
  • Setaria (Setaria sphacelata)
  • Signal grass (Brachiaria decumbens syn. Urochloa decumbens)

There are potentially more grass species that are affected.

Cause

Research to date indicates that pasture dieback is not caused by a single agent, but likely a complex interaction of multiple agents and factors. Research to identify the causal agents is continuing.

Two insects are currently also under investigation for their role in the condition: pasture mealybug (Heliococcus sp. nr summervillei) and white ground pearl (Margarodes australis). Pasture mealybug has been found at pasture dieback sites in NSW. The association of both insects with pasture dieback is currently being studied.

Control options

A number of techniques have been tested to control pasture dieback but to date, no successful methods have been identified that consistently restore long-term pasture productivity. Burning and cultivation have been found to provide short-term relief of symptoms only. Research is ongoing.

Pasture mealybug is a pest of pasture grasses irrespective of its role in pasture dieback. APVMA have released an emergency permit (PER88482) for the use of the systemic insecticide spirotetramat (registered as Movento®) for the control of pasture mealybug in mixed pastures. This insecticide is best used for small incursions only. Before using the insecticide ensure that pasture mealybug is present. It is important to read and adhere to the APVMA permit and Movento® label.

Maintaining productivity with alternative forages

The death of pastures due to pasture dieback can lead to feed shortages, low ground cover and colonisation by weeds. Sowing alternative forages into these affected areas will provide valuable feed, as well as maintain ground cover to prevent erosion and provide competition for weeds.

Broad-leaf plants are not affected by pasture dieback. Legumes, herbs and brassicas are options that can be sown into dieback affected areas. Talk to your local advisor about which species and varieties are best suited to your situation.

At this stage we do not recommend re-sowing perennial grasses into dieback affected areas. All of the summer growing perennial grass species commonly sown in NSW are susceptible to pasture dieback while the susceptibility of temperate species is not known.

Suggested options sowing options and the susceptibility to pasture dieback are listed in the table below.

Forage typeSusceptibility to pasture diebackNotes and further information
Winter annual legumes (e.g. clovers, medics, vetch, serradella, biserrula)Nil

Species information

Pasture variety guide

Summer forage legumes (e.g. cowpeas, lablab, soybeans)Nil

Summer legume forage crop

Perennial legumes (e.g. lucerne, white clover, red clover, desmanthus, creeping vigna, forage peanuts)Nil

Species information

Pasture variety guide

Herbs (e.g. chicory, plantain)Nil

Chicory

Plantain

Brassicas (e.g. forage rape, leafy turnip, bulb turnip)NilForage brassicas
Winter cereals (e.g. forage or dual purpose types. Oats, wheat, barley, triticale, rye)Unknown

To date no reported cases of pasture dieback in winter cereals.

Winter crop variety sowing guide

Annual winter grasses (e.g. annual ryegrass)UnknownThere has been one reported case of annual ryegrass affected by pasture dieback. If sowing ryegrass use a cheap variety. Seed treatment may provide extra protection.

Summer forages (e.g. millet, forage sorghum)

Unknown

There have been mixed reports in Queensland. Seed treatment may provide extra protection.

Forage sorghum and millet

Perennial temperate grasses (e.g. perennial ryegrass, fescue, cocksfoot, phalaris)UnknownNot recommended to sow. High establishment cost when susceptibility is unknown.
Perennial tropical grasses (e.g. kikuyu, paspalum, setaria, Rhodes grass, panic grasses, digit grass)Very highNot recommend to sow. All species commonly sown in NSW are affected by dieback.

Pasture dieback can occur in both arable and non-arable landscapes. In areas which are too steep for machinery access or populated by trees, alternative strategies will be required. In some situations broadcasting seed may be an option. In areas where access is limited, regular grazing of the pasture could minimise spread of the condition into unaffected paddocks. In Queensland, some pastures have regenerated from the soil seedbank without intervention. Research is required in these situations to identify suitable solutions.

Actions to minimise spread

Put in place best practice biosecurity actions to prevent entry, establishment and spread of pasture dieback on your property:

  • practise “Come clean. Go clean”
  • ensure all staff and visitors are instructed in and adhere to your business management hygiene requirements
  • monitor your grass pastures and crops regularly
  • keep records

Movement of pasture dieback affected grass hay is a potential means of spread. Source hay from reputable suppliers, especially pasture grass hay e.g. Rhodes grass. Monitor areas where hay is stored and fed.

Reporting pasture dieback

Help us identify where pasture dieback is by reporting. If you suspect symptoms of pasture dieback please:

  • Contact the Exotic Plant Pest hotline on 1800 084 881
  • Email biosecurity@dpi.nsw.gov.au with a clear photo and your contact details or
  • Complete the online reporting form

Further reading

References

Buck, S. & Johnstone, C. (2019) Pasture dieback. Department of Agriculture and Fisheries, Queensland. https://futurebeef.com.au/knowledgecentre/pasture-dieback/