Pasture dieback — management options
- There are no one-size-fits-all strategies to manage pasture dieback. Each situation needs to be individually assessed to determine the best course of action; what is suitable for your neighbour might not be suitable for you.
- Ensure paddocks are continually monitored for spread, or recovery.
- Assess the costs and practicalities of management strategies versus the potential of a new pasture naturally regenerating over time.
- If treatment is conducted, incorporating tolerant annual forages or perennial legume-grass pastures into the paddock is likely to be more cost-effective in the long-term than directly treating pathogenic organisms.
Pasture dieback is currently impacting the productivity of tropical pastures in areas of eastern Queensland and north-eastern New South Wales. The condition is characterised by patches of otherwise healthy, productive grasses first exhibiting leaf discolouration (yellowing, reddening, or both), followed by unthrifty growth and senescence, resulting in premature death. There are numerous other conditions that can cause similar symptoms, however dieback is usually defined by grasses dying in patches for no other obvious reason (e.g. water or nutrient stress, soil or grazing variations).
There are multiple factors that may be involved with this condition:
- Environmental stress (e.g. soil and climate)
- Paddock management (e.g. grazing practices such as rotation, set stocking)
- Biological pathogen (e.g. virus, bacteria, fungi or insects)
Research indicates biological pathogenic organisms are the most likely cause. However, in some situations environmental and managerial factors also appear to be contributing. This article aims to provide recommendations based on current knowledge. Updates will be produced as new information becomes available. Two commonly asked questions will be addressed:
- What can I do so I don’t get pasture dieback?
- What can I do if I have pasture dieback?
1. What can I do so I don’t get pasture dieback?
It’s unlikely anything can be practically done to stop pasture dieback affecting specific paddocks or properties. While reducing pasture yield for periods of time could lessen the risk, beef production in extensive grazing systems relies on growing as much pasture as possible during the wet season, which is then used during the dry season. Grazing management needs to ensure pasture consumption (stocking rate) matches pasture growth without going to extremes – i.e. major pasture deficit and no ground cover, or a large surplus of pasture that is conducive to pasture dieback conditions.
There is high potential for pasture dieback when the following factors are present:
- The paddock is located within a known dieback area, currently eastern Queensland (or north-eastern New South Wales) with average annual rainfall higher than 600mm per annum.
- The pasture contains improved tropical grass species.
- Favourable soil and climatic conditions occur which enable moderate-to-high pasture yield in most years.
- Pasture yield is consistently moderate-to-high from conservative stocking rates or no grazing (e.g. areas fenced off to stock).
2. What can I do if I have pasture dieback?
If a paddock has been affected by dieback, there are several aspects to consider.
- What is the scale of the issue?
- How big is the area affected?
- How many patches or areas are affected?
- How many paddocks are affected?
- Is the affected area expanding, contracting, or static?
- What stage is the dieback at (just started, mid-stage, or dead grass)?
- Are the affected paddock(s) cleared and open, or timbered (lightly or heavily)?
Strategies are separated into two categories:
a) Small area impacted and is still spreading
b) Large area impacted and either spreading or
continuing to affect pastures
a) Small area impacted and still spreading. Options include:
- Don’t treat. Monitor to assess further progress and if edible plants are remaining or are emerging. Graze by matching stocking rate to pasture production.
- Graze the paddock to use remaining available feed, then spell.
- Slash or burn the paddock (only when at very early dieback stage), then spell for recovery.
- Monitor to determine if mealybugs are present. Obtain professional advice to assess level of impact, whether predators are present, and if spraying will be an effective solution.
If spraying is deemed the best option, strictly follow the Australian Pesticides and Veterinary Medicines Authority permit requirements relevant to the selected chemical. These are generally:
- Spray juvenile-stage insects only, not adults.
- Only spray an actively growing pasture, but not if flowering.
- Ensure thorough coverage of all plant surfaces and crown of the plant.
- Do not spray if bees are present, or if beneficial insects have been released.
- Application only by ground rig.
- Adhere to any grazing exclusion/withholding periods (some are very long).
There are multiple factors to consider when deciding to spray insecticide. These include:
- Product cost and cost/difficulty of spraying extensive areas.
- Risk of insecticide residue in meat if grazing exclusion/withholding periods are not adhered to.
- Probability of poor effectiveness in moderate-high biomass pastures (spray doesn’t cover the whole plant).
- Potential of insects to reinfect the paddock from nearby untreated areas.
- The likelihood of beneficial insects being able to manage pest populations and the negative impacts if spraying occurs.
As such, spraying should only be considered a last resort option for small patches.
- Developing, modifying, or adhering to an existing farm biosecurity plan should help minimise the chance of dieback being introduced onto the property through normal business activities.
Best-bet option for small areas: Graze the paddock to utilise remaining feed, spell and monitor.
b) Large area impacted and dieback is either spreading or continuing to affect pastures. Options include:
- Don’t treat. Allow/encourage natural regeneration of a new pasture. Monitor to determine percentage of edible pasture plants (less susceptible grass species, forbs, legumes, etc), and graze sparingly to encourage thickening.
- Remove remaining pasture/weeds with herbicides or cultivation, fallow to store sufficient soil-moisture, determine fertiliser needs, and re-seed with either:
- perennial legumes only (see Incorporating legumes for more profitable beef production)
- perennial legumes with a less susceptible grass
- annual forages (e.g. forage sorghum, lablab, or oats), then sow a perennial legume and less susceptible grass the year after.
- If paddocks are heavily timbered or machinery access is difficult, then consider aerial application of suitable treatments, or treating areas where machinery can access (i.e. zonal management).
- Burn the paddock (only when at very early dieback stage), then spell for recovery.
- Develop, modify, or adhere to an existing farm biosecurity plan to minimise the chance of dieback being brought onto and spread throughout the property through normal business activities.
Best-bet option for large areas: Undertake detailed assessment to determine if re-seeding is more cost effective versus not treating and allowing natural regeneration to occur.
For more information
The Department of Agriculture and Fisheries (DAF) team is encouraging graziers affected by dieback (existing, new, or recovered) to make contact. This will help us understand this condition better, and to provide any available assistance. Please call the DAF Customer Service Centre on 13 25 23.
Stakeholders are always welcome to visit your local DAF office and talk to an extension officer.
Related pasture dieback information
- Pasture dieback factsheets (March 2021)
- Calling graziers who want to increase knowledge and ability to combat pasture dieback!
- Pasture dieback research update (May 2020)
- Latest insights into pasture dieback webinar recording (February 2019)
- Pasture dieback: past activities and current situation across Queensland report
- Sown pasture rundown
- Pasture dieback (Meat & Livestock Australia)