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Now’s the time to check for pasture dieback

03 December 2020

Pasture dieback can be difficult to identify but summer is the best time of year to get out in the paddock and check for it.

During the growing season, (spring to autumn) pasture dieback becomes easier to identify, particularly after a significant rainfall event because it’s obvious where pasture simply isn’t growing.

Here, we talk to Stuart Buck from the Queensland Department of Agriculture and Fisheries (DAF) to find out how to identify pasture dieback, possible strategies to combat dieback and what research is in the pipeline to help producers.

How to identify pasture dieback

“Pasture dieback is difficult to identify because some conditions such as nutrient or water stress look similar especially in the initial stages, so you need to monitor the symptoms right through to plant death,” Stuart said.

“Observe patches that could be affected over a period of time. The initial stages of pasture dieback cause leaf discoloration such as reddening or yellowing of leaves.

“In the second stage you’ll notice the pasture isn’t growing, leaves wilt and senesce early. Then during the last stage plants slowly die overtime which can be as short as a couple of weeks or it might take a few months.”

Pasture dieback can affect small numbers of plants in patches or sometimes whole paddocks. Refer to Table 1 for the different species of pasture affected by pasture dieback.

Table 1: Pasture species affected by pasture dieback

Region  Queensland NSW
Pasture species Buffel grass Broad leaf paspalum
Sabi grass Bahia grass
Creeping blue grass Giant paspalum
Rhodes grass Setaria cv Kazungula
Panics  Rhodes grass cv Katambora
Paspalum Couch*
Signal grass Kikuyu*
Para grass Carpet grass*
Pangola grass  
Seteria
Black spear Grass
Forest blue grass
Golden beard grass

* denotes pastures which have only shown symptoms, and not pasture death.

Source: DAF and NSW DPI

Where is pasture dieback more common?

Pasture dieback has been identified in northern NSW and Queensland, generally east of the Great Dividing Range, up the coastal and adjacent inland fringe through to the Atherton Tablelands.

“Pasture dieback is commonly seen in higher rainfall areas receiving more than 600mm annual average and in areas with productive pastures,” Stuart said.

“For example, pasture dieback is common if there is a large body of grass where grazed paddocks have been spelled for a long period of time, or in non-grazed areas such as roadsides.”

How does pasture dieback affect production?

Pasture dieback can have a range of devastating impacts for producers and the whole red meat supply chain:

  • direct impact on pasture yield means less cattle
  • cost to re-sow a pasture or apply a treatment to fix the problem
  • reduced stocking rates means less cattle through the red meat supply chain.

Five strategies to combat pasture dieback

Although multiple pathogenic organisms including pasture mealybug are observed to be associated with dieback, all the underlying factors involved in cause and affect haven’t been identified yet.

Here are five strategies producers can use to combat pasture dieback:

  1. If the area affected remains small and not accessible with machinery, it’s best to leave it and see what happens as pasture regeneration can occur.
  2. If pasture mealybug can be seen, especially at the outer edges of affected areas, then multiple insecticide options are now available including MOVENTO (spiroteramat). Apply according to label instructions and adhere to the grazing withholding periods specific to each product.
  3. If the area is accessible to machinery, resowing a new pasture including legumes or annual forages (e.g. broad leaf forage such as brassicas, forage oats or sorghum) are options to restore productivity. These have been observed to be either unaffected or more tolerant to dieback.
  4. If the area isn’t accessible with machinery, change grazing management strategies, reduce stocking rates and monitor the condition over time.
  5. Utilise pastures at sustainable levels. Avoid accumulating large amounts of pasture yield by spelling pastures for long periods of time – this could reduce the potential for pasture dieback.

New project aims to improve knowledge and identify and manage pasture dieback

DAF is conducting a new project co-funded by MLA to help producers accurately identify and diagnose pasture dieback on their property and understand the practices to combat pasture dieback.

“The project has formed a producer group called the Pasture Dieback Industry Network (PDIN),” Stuart said.

“This is a network of producers and industry across Queensland interested in pasture dieback. We will be extending our latest findings through this network so register via the FutureBeef website to receive monthly and other updates.

“Producers will be taken through a tailored action learning process where knowledge is improved to facilitate practice change on-farm.”

A learning package will be developed specifically for the group including:

  • learning materials (monthly e-newsletter and fact sheets)
  • data-recording resources
  • multiple on-farm demonstrations and trials
  • engagement of the broader grazing community e.g. field days.

New project to identify the causes of pasture dieback

MLA has also co-funded DAF to undertake further field sampling and diagnostic analysis to help narrow down the causes of pasture dieback.

“There may not be a single causal agent in pasture dieback, so this project focuses on analysis of a range of pathogenic organisms,” Stuart said.

The project will analyse a number of potential organisms, some of which haven’t been investigated before. These include:

  • what viruses are present in pastures affected by pasture dieback
  • the biological aspects (microbiome) of soils, roots and plants affected by pasture dieback
  • different types of fungi
  • mealybugs. 

Both projects are due for completion in June 2021 and will provide recommendations on pasture management strategies that could be adopted to mitigate pasture dieback.