Updated: March 2024
Pasture dieback is a condition that kills sown and native summer growing grass 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. Dieback was confirmed in inland NSW in autumn 2024 in the Boggabilla region.
Symptoms are most evident when grasses are actively growing during spring, summer and autumn, especially following significant rainfall. Symptoms of pasture dieback include:
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.
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:
There are potentially more grass species that are susceptible.
Research to date indicates that pasture mealybug (Heliococcus summervillei) is associated with pasture dieback. Pasture mealybugs are small. The adult females are easiest to see with the naked eye (Figure 3). They are white or pink-ish and 2-3 mm long. Pasture mealybug can be found on growing symptomatic grass species. Often, they can be found on the underside of leaves as well as on the ground, in leaf litter and among the roots.
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.
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.
Broadleaf 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.
All of the summer growing (tropical) perennial grass species commonly sown in NSW are susceptible to pasture dieback. Winter growing (temperate) grasses do not appear to be susceptible.
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.
Put in place best practice biosecurity actions to prevent entry, establishment and spread of pasture dieback on your property:
Help us identify where pasture dieback is by reporting. If you suspect symptoms of pasture dieback please:
Buck, S. & Johnstone, C. (2019) Pasture dieback. Department of Agriculture and Fisheries, Queensland. https://futurebeef.com.au/knowledgecentre/pasture-dieback/