Pasture dieback
Updated: March 2024
Read the Pasture dieback identification guide
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 New South Wales. Pasture dieback was confirmed on the North Coast of NSW in autumn 2020. Over the last four years it has spread on the North Coast, south to Grafton and west to Tabulam. We are also monitoring northwest NSW for 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. It starts with the oldest leaves and typically begins at the leaf tip and moves along the leaf blade towards the stem (Figure 2).
- Affected plants become stunted and unthrifty. These 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 affected 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 symptoms can be caused by a range of other factors. These include but are not limited to: 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. More information on symptoms can be found in the pasture dieback identification guide.
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.
Species known to be affected include:
- African Lovegrass (Eragrostis curvula)
- 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 susceptible.
Cause
Research to date indicates that pasture mealybug (Heliococcus sp. nr summervillei) is involved in pasture dieback, but it is likely a complex interaction of multiple agents and factors. Research to identify the causal agents is continuing.
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.
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 sowing options and the susceptibility to pasture dieback are listed in the table below.
| Forage type | Susceptibility to pasture dieback | Notes and further information |
|---|---|---|
| Winter annual legumes (e.g. clovers, medics, vetch, serradella, biserrula) | Nil | |
| Summer forage legumes (e.g. cowpeas, lablab, soybeans) | Nil | |
| Perennial legumes (e.g. lucerne, white clover, red clover, desmanthus, creeping vigna, forage peanuts) | Nil | |
| Herbs (e.g. chicory, plantain) | Nil | |
| Brassicas (e.g. forage rape, leafy turnip, bulb turnip) | Nil | Forage brassicas |
| Winter cereals (e.g. forage or dual purpose types. Oats, wheat, barley, triticale, rye) | Nil | To date no reported cases of pasture dieback in winter cereals. |
| Winter annual grasses (e.g. annual ryegrass) | Nil | There has been one reported case of annual ryegrass affected by pasture dieback. If sowing ryegrass use an inexpensive variety. Seed treatment may provide extra protection. |
Summer forages (e.g. millet, forage sorghum) | Nil | There have been mixed reports in Queensland. Seed treatment may provide extra protection. |
| Temperate perennial grasses (e.g. perennial ryegrass, fescue, cocksfoot, phalaris) | Unlikely | Not recommended to sow. High establishment cost when susceptibility is unknown. |
| Tropical perennial grasses (e.g. kikuyu, paspalum, setaria, Rhodes grass, panic grasses, digit grass) | Very high | Not 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
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
- Pasture dieback identification guide
- Pasture dieback (MLA)
- Pasture dieback in Queensland (QDAF)
- Mealybug fact sheet (QUT)
References
Buck, S. & Johnstone, C. (2019) Pasture dieback. Department of Agriculture and Fisheries, Queensland. https://futurebeef.com.au/knowledgecentre/pasture-dieback/
