Pasture dieback

Pasture dieback is a condition killing large areas of sown and native summer growing pasture in Queensland. The size of areas affected varies. It starts as small patches and can spread to affect large areas. In some cases whole farms have been affected. It is not limited by landscape or soil type. Livestock avoid grazing these areas making them unproductive (Figure 1).

Pasture dieback was first identified in Central Queensland and has now spread from Far North Queensland to the NSW border. Suspected pasture dieback was reported on a property in northern NSW in autumn 2019.


Pasture dieback

Species affected

Pasture dieback affects summer growing grasses, both sown and native. It has not been reported in temperate grasses, with the exception of a single case of an annual ryegrass forage crop.

Sown species known to be affected include:

  • Buffel grass (Cenchrus ciliaris)
  • Digit grass (Digitaria eriantha)
  • Rhodes grass (Chloris gayana)
  • Green and Gatton panic (Megathyrsus maximus)
  • Bambatsi panic (Panicum coloratum)
  • Kikuyu (Pennisetum clandestinum)
  • Paspalum (Paspalum dilatatum and P. plicatulum)
  • Creeping bluegrass (Bothriochloa insculpta)
  • Sabi grass (Urochloa mosambicensis)
  • Signal grass (Brachiaria decumbens syn. Urochloa decumbens)
  • Para grass (Brachiaria mutica syn. Urochloa mutica)
  • Setaria (Setaria sphacelata)
  • Purple pigeon grass (Setaria incrassata)
  • Forest bluegrass (Bothriochloa bladhii ssp. glabra)
  • Indian couch (Bothriochloa pertusa)

Other species known to be affected include:

  • Black spear-grass (Heteropogon contortus)
  • Forest bluegrass (Bothriochloa bladhii)
  • Golden beard grass (Chrysopogon fallax)
  • Giant rat’s tail grass (Sporobolus pyramidalis)

There are potentially more grass species that could be affected.

What to look for

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

  • Yellowing, reddening and purpling of leaves. 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 m. Patches grow and merge and affect large areas.
  • Rapid increase in size of the infected area following significant rainfall in spring-autumn.
  • Eventually the infected 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, drought, 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

Cause

It appears to be the result of a complex interaction of multiple contributing factors, including environmental conditions. A couple of insects are currently also under investigation.

Control

A number of techniques have been tried to control pasture dieback but no successful outcome has been resolved to date. Research is ongoing.

Actions to minimise

Movement of affected grass hay is one potential cause of spread.  Source hay from reputable suppliers, especially pasture grass hay e.g. Rhodes grass.

Put in place best practice biosecurity actions to prevent entry, establishment and spread:

  • 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

Further information and reporting of pasture dieback

If you suspect symptoms of pasture dieback you can:

  • 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