Net form net blotch (NFNB)

Pyrenophora teres f. teres


disease pressure


fungicide use


with extension

Net form net blotch (NFNB)
Pyrenophora teres f. teres


Net form of net blotch (NFNB) is an important and increasingly frequent disease of barley across all growing regions, especially in medium to high rainfall zones of South Australia and Western Australia.

It is particularly damaging in wetter years, in systems with high inclusion of susceptible barley in rotations, and where barley is sown into barley stubble. Severe infections can cause 20-50% yield loss and significant reduction in grain quality.

NFNB is typically favoured by susceptible hosts, early sowing, mild weather (15-25°C) and extended periods of leaf wetness. It survives between seasons on stubble, volunteer plants and seed.


Resistance Group 3 fungicides propiconazole, prothioconazole and tebuconazole in the Esperance and Kwinana West port zones of WA.

ResistanceGroup 7 (SDHI) fungicide fluxapyroxad on the Yorke and Eyre Peninsulas and Kybybolite region, SA. 

Reduced sensitivity  – Group 3 fungicides epoxiconazole, propiconazole, prothioconazole and tebuconazole in SA and WA. 

Reduced sensitivity  – Group 7 (SDHI) fungicide fluxapyroxad in SA. 

Dual resistance/reduced sensitivity  – both reduced sensitivity to the Group 3 fungicide tebuconazole and resistance to the Group 7 fungicide fluxapyroxad on the Yorke Peninsula, SA. 

Lab detectiondual resistance to both Group 3 fungicide tebuconazole and Group 7 fungicide fluxapyroxad on the Yorke Peninsula, SA. 


Net form net blotch

Net form net blotch is an important disease of barley across all growing regions of Australia, especially in mid to high rainfall zones of SA and WA. NFNB has repeatedly developed fungicide resistance and reduced sensitivity under barley-on-barley rotations. Careful use and rotation of available fungicides will lessen the spread of resistance in net blotches.

Barley net form of net blotch Group 11 (Qol) fungicide resistance

Researchers have detected a mutation in NFNB affecting Group 11 (Qol) fungicides in barley samples collected in SA. While the mutation has not been associated with paddock fungicide failure, the discovery means all three fungicide Mode of Action groups are now compromised in barley limiting the options for chemical control of NFNB outbreaks. This fact sheet provides more information about the mutation and its implications.

Fungicide resistance in barley

Net form net blotch, spot form net blotch and powdery mildew are important diseases of barley that have exhibited fungicide resistance. All fungal diseases of barley have the potential to develop resistance to any single-site fungicide that is used repetitively. Adopting integrated disease management and fungicide usage practices now will help preserve the effectiveness of these useful chemicals.

Fungicides in Australia

Fungicides are a valuable tool in crop protection worldwide. However, most are vulnerable to the pathogens they target developing fungicide resistance, so responsible management is essential for preserving ongoing efficacy. There is a limited number of fungicide Mode of Action groups registered for use on crops in Australia.

Fungicide resistance

Fungicide resistance is a serious issue that can affect crop yields in the short term, while impacting on the long term viability of registered fungicides. Understanding how fungicide resistance develops, how it places additional pressure on other fungicides, and how fungicide use should be managed to minimise risk is vital for protecting future crop yields.

SDHI resistance in barley net blotches

Succinate dehydrogenase inhibitors, or SDHIs, are some of the most effective chemistries to grace the market in recent years for the management of net blotches in barley. The problem is, they are already under strain in the Southern and Western Regions.

Northern region

Southern region

Western Region


AFREN case study – net form net blotch

AFREN case study – net form net blotch

Barley growers on South Australia’s Yorke Peninsula have seen how quickly fungicide resistance can turn from a potential problem to serious threat in the absence of good management practices.

Sam Holmes is an experienced agronomist in the region, where barley has proven to be a reliable and economically successful crop over many years.

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Monday 14 August 2023

AFREN Fungicide Resistance Update Webinar - Qld: University of Southern Queensland researchers Professor Levente Kiss and Dr Noel Knight and the CCDM's Dr Fran Lopez Ruiz provide an update on fungicide resistance detections in mung bean powdery mildew, net blotches and wheat powdery mildew in Qld.

Southern region webinar

Monday 16 August 2021

Australian Fungicide Resistance Extension Network (AFREN) Fungicide Resistance in Southern Region webinar with Dr Tara Garrard (SARDI), Nick Poole (FAR Australia) and Steve Marcroft (Marcroft Grains Pathology).‏‎ ‎


Western region webinar

Thursday 19 August 2021

AFREN Fungicide Resistance WA webinar with Dr Fran Lopez-Ruiz from the Centre for Crop Disease Management (CCDM) and DPIRD specialists Geoff Thomas, Dr Kithsiri Jayasena and Andrea Hills.


WA webinar

Thursday 27 August 2020

AFREN Fungicide Resistance in WA presented by Geoff Thomas, DPIRD, with CCDM's Wes Mair and Fran Lopez Ruiz and Kith Jayasena, DPIRD.

Victoria webinar

Wednesday 26 August 2020

Australian Fungicide Resistance Extension Network (AFREN) Fungicide Resistance in Victoria webinar by Grant Hollaway, Agriculture Victoria.‏‏‎ ‎

High Rainfall Zone webinar

Tuesday 4 August 2020

Australian Fungicide Resistance Extension Network (AFREN) Fungicide Resistance in the High Rainfall Zone webinar led by Nick Poole from FAR Australia.‏‏‎ ‎

NSW/Qld webinar

Friday 24 July 2020

Australian Fungicide Resistance Extension Network (AFREN) Fungicide Resistance in NSW/Qld webinar by Steven Simpfendorfer, NSW DPI, Lisle Snyman, DAFQ and Levente Kiss, Centre for Crop Health, USQ.

SA webinar

Thursday 2 July 2020

Australian Fungicide Resistance Extension Network (AFREN) Fungicide Resistance in SA webinar led by Dr Tara Garrard and Dr Hugh Wallwork, plant pathologists with SARDI.‏‎ ‎


The why and how of rotating fungicides to minimise the risk of resistance

In this AFREN 2 podcast, Associate Professor Fran Lopez, CCDM, Curtin University, talks about the importance of rotating fungicides to minimise the risk of fungicide resistance developing in your paddocks. He outlines strategies for growers to implement on farm.

Fungicide risk factors

While farmers typically spray fungicide to manage one disease, Dr Steven Simpfendorfer explains how spraying one pathogen can inadvertently encourage resistance in other pathogens that may be present. Some typical examples include rusts and powdery mildew in wheat; blackleg and sclerotinia in canola; and net blotches and powdery mildew in barley.

Applying fungicide for economic return

Nick Poole from FAR Australia provides an excellent explanation of how to target fungicide applications for the best economic return. He describes the value of focusing on critical growth stages and their ‘money leaves’, the best way to manage disease risk in crops before tillering, and the importance of protecting fungicide effectiveness for the long term.

Fungicide resistance in the south

South Australian grain growers have been alerted to several cases of fungicide resistance in recent growing seasons, including in net form net blotch of barley, and wheat powdery mildew.

In this podcast, Dr Hugh Wallwork, from the South Australian Research and Development Institute, the Department of Primary Industries and Regions’ research division, talks about the factors that contribute to fungicide resistance and how fungicide management needs to begin with variety and seed treatment selection before sowing.

He explains that growers should be using all available agronomic practices to reduce disease pressure and should avoid repeat applications of a single fungicide active or chemical Mode of Action. This will help protect the effectiveness and availability of their essential fungicide controls.

Fungicide resistance in the west

In WA, outbreaks of fungicide resistance have occurred in several important diseases of barley. Resistance is a significant but preventable problem that can largely be managed by taking care not to repeatedly expose a pathogen to the same product or chemical Mode of Action Group.

It is important for growers to recognise that this management regime can include fungicide seed treatments and in-furrow fungicide applications, as well as foliar sprays later in the season. Fungicide rotations to manage and prevent fungicide resistance need to take all of these applications into account.

Geoff Thomas, plant pathologist from the Department of Primary Industries and Regional Development WA, discusses the importance of using an integrated disease management program to reduce disease pressure and manage fungicide use and resistance in WA cropping systems.

Fungicide Resistance Five podcast series

The ‘Fungicide Resistance Five’ is the basis for an integrated disease management strategy that growers can use on-farm to reduce fungicide resistance pressure on crop pathogens.

This six-part podcast series, produced through the Australian Fungicide Resistance Extension Network (AFREN), unpacks the individual elements of the strategy to inform growers why and how they should minimise the risk of fungicide resistance developing in their paddocks.

AFREN is a significant GRDC investment that brings together a national network of regional plant pathologists, fungicide resistance experts and communications and extension specialists. It is co-ordinated through the Centre for Crop Disease Management (CCDM), a co-investment between the GRDC and Curtin University.

General fungicide resistance management

Dr Kylie Ireland, first Extension Coordinator of Australian Fungicide Resistance Extension Network (AFREN), discusses how fungicide resistance occurs, its potential impact on crop production, and how the Fungicide Resistance Five can help growers mitigate their risk.

Avoiding susceptible crop varieties

How does variety selection help slow fungicide resistance? Dr Grant Hollaway points out how planting crop varieties with genetic resistance to frequently occurring diseases can reduce disease pressure and an unhealthy reliance on fungicides.

The value of crop rotation

Long-practiced crop rotations are an effective non-chemical means of reducing (or even eliminating) soil and stubble borne fungal pathogens in paddocks. DPIRD plant pathologist Geoff Thomas discusses the continued importance of practicing crop rotation for disease control.

Non chemical strategies to reduce disease pressure

South Australian plant pathologist Dr Tara Garrard covers the range of agronomic practices growers have at their disposal to reduce disease pressure, limit fungicide applications and lower the risk of promoting fungicide resistance in their crops.

Strategic fungicide applications

Fungicides remain a valuable and powerful tool for managing crop disease and FAR Australia Managing Director Nick Poole explains how to identify the right times to apply fungicide for maximum effect and economic benefit.

Fungicide / Mode of Action rotation and mixtures

Using fungicide mixtures and rotating Mode of Action groups is vital to eliminate resistant pathogen strains. Fungicide resistance specialist Dr Fran Lopez-Ruiz from Centre for Crop Disease Management at Curtin University highlights the importance of a dynamic spray program.


Management techniques to minimise fungicide resistance risk in the medium rainfall zone

Dr Tara Garrard, SARDI

“The more spores of a pathogen in a paddock, the higher the chances of fungicide resistance developing … we need to keep the levels of inoculum as low as possible.” Consider the fungicide resistance management pyramid when making crop management decisions.

AFREN Fungicide Resistance Five


The Fungicide Resistance Five is an integrated disease management strategy to reduce disease pressure and minimise reliance on fungicides for disease control.


AFREN Fungicide Resistance Pyramid


Fungicides are at risk of developing resistance but there are cultural and non-chemical options to consider before applying. The AFREN is a useful management tool.