Event to address resistance in key barley disease

Author: | Date: 15 Feb 2019

image of Wesley Mair
CCDM Fungicide Resistance Management and Disease Impact Theme leader Fran Lopez-Ruiz, left, with CCDM researcher Wesley Mair. Photo by CCDM.

Management strategies to help grain growers minimise the development of fungicide resistance in one of Australia’s most damaging barley diseases will be a focus at the Grains Research and Development Corporation (GRDC) Grains Research Update in Perth later this month.

Centre for Crop and Disease Management (CCDM) Fungicide Resistance Management and Disease Impact Theme leader, Fran Lopez-Ruiz, will speak about fungicide resistance in spot form of net blotch (SFNB) at the event on February 25 and 26.

CCDM research into SFNB is supported by GRDC investment, with this latest work also involving the Department of Primary Industries and Regional Development (DPIRD) and the Foundation for Arable Research in Australia.

“The control of fungal diseases in broadacre crops is often very reliant on the use of fungicides, but their continuous application has led to the development of resistance in fungal pathogens,” Dr Lopez-Ruiz said.

“Fungicide resistance increases management costs and impacts on farm profitability.”

Dr Lopez-Ruiz said fungicide resistance to some Group 3 DeMethylation Inhibitors (DMI) fungicides in SFNB, a disease caused by the pathogen Pyrenophora teres f. maculata, was present in southern grain growing regions of Western Australia.

He said sampling work detected SFNB strains moderately resistant to fungicide in the Esperance region from 2016 onwards, and highly resistant strains in the Great Southern and Esperance regions from 2017 onwards.

Dr Lopez-Ruiz said control measures for SFNB were the application of effective fungicides and the use of varieties that contained genetic resistance to the disease, as well as cultural control measures (practices that reduce disease establishment, reproduction, dispersal and survival).

“However, due to the current lack of highly resistant cultivars, SFNB is controlled mainly using fungicides,” he said.

Dr Lopez-Ruiz said growers needed to take a cautious approach with controlling SFNB and implement adequate integrated disease management strategies to minimise the ongoing selection of SFNB resistant populations.

“Being a stubble-borne disease, rotating crops or managing stubble are paramount for reducing disease carry-over, and selecting varieties that have disease resistance will reduce the severity of SFNB during the growing season,” he said.

“However, these measures will not be very effective unless growers choose fungicides carefully.

“Any spray program that is heavily dependent on Group 3 fungicides will increase the risk of resistant populations developing.

“I encourage growers to use seed dressings, as well as in-furrow and foliar products containing fungicide mixtures from different chemical groups (Groups 3, 7 and 11), and to remove tebuconazole from control programs in areas where resistance has been found.

“This will help to limit the spread of resistance in SFNB and its emergence in other barley growing regions of Australia.”

In addition to using cultivars with good disease resistance levels, other cultural practices that growers can use to limit the development of resistance in SFNB include using disease-free seed; employing stubble management strategies to reduce the disease load; rotating crops; grazing with livestock; and maintaining good farm hygiene.

The following chemical management strategies are also recommended:

  • Only spray if necessary – limit applications
  • Choose fungicide mixtures with different modes of action (if available)
  • Never apply the same Group 3 fungicide consecutively
  • Avoid consecutive applications of fungicides with the same mode of action from Groups 7, or Succinate dehydrogenase inhibitor (SDHI), and Group 11, or quinone outside inhibitors (Qol)
  • Incorporate the use of seed dressings (Group 7), in-furrow (Group 11) and foliar products containing fungicide mixtures from different chemical groups (such as Groups 3 (DMI), 7 (SDHI) and 11 (Qol) – in combination with limited use of propiconazole and no stand-alone tebuconazole use
  • Ideally use DMI-based mixtures (e.g. Prosaro® containing prothioconazole and tebuconazole) only once, followed by mixtures containing other actives (preferably from groups 7 or 11)
  • If resistance is present or suspected, avoid or minimise use of that mode of action, as continuing its use will only further select for resistance
  • Do not exceed label rates.

More information about SFNB management is available in the GRDC western region Barley GrowNotes™ at https://grdc.com.au/grownotes.

Contact Details

For Interviews

Carole Kerr, CCDM Manager, Communications
08 9266 4818 / 0437 538 541


Natalie Lee, GRDC Communications Manager West
0427 189 827

GRDC Project code: CUR00016, CUR00023