Resources – Fact sheets

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.

Numerous cases of reduced sensitivity and resistance to fungicides have been identified in Australia’s wheat growing regions. More cases are expected to arise as survey and detection methods improve, and if current fungicide use patterns continue. Fungicide resistance is a preventable issue, caused by repeatedly exposing a pathogen to a single fungicide active or to the chemical actives of a single Mode of Action (MoA) group.

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

Populations of the fungal pathogen causing blackleg on canola have exhibited reduced sensitivity to several common Group 3 (DMI) fungicides across most growing regions of Australia. The field implications of this finding are currently unknown, but it does increase the risk of full resistance to DMI fungicides evolving if these fungicides are misused. The DMI fungicides will be less effective towards these isolates but will still provide some control.

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.

Spot form net blotch is an important disease of barley across all growing regions of Australia. It can be especially damaging in southern regions during wetter seasons. Numerous cases of fungicide resistance or reduced sensitivity in SFNB have been detected in locations across the Western and Southern growing regions, with several Group 3 (DMI) and Group 7 (SDHI) fungicides being affected.

Wheat powdery mildew is caused by the fungal pathogen Blumeria graminis f. sp. tritici. It is a sporadic disease but, in years with conducive conditions and especially in the southern and northern region, it can cause significant yield losses.  Careful use and rotation of available fungicide actives will help control the spread of  resistance in wheat powdery mildew.

Septoria tritici blotch is caused by the fungal pathogen Zymoseptoria tritici. It is an important disease, particularly in high rainfall areas of the southern growing region, where it can cause yield losses of around 40% under conducive conditions. There have been several cases of STB developing full resistance to fungicides globally and they must be used with care in Australia to protect continued effectiveness.

Ascochyta blight of lentils is caused by the fungal pathogen Ascochyta lentis and is an important disease in Australia, especially in the southern growing region. The disease can infect seed pods, potentially causing seed staining or seed abortion. Economic losses may result due to reduced grain quality and unprotected crops can suffer yield losses of 50% or more.