Understanding fungicide resistance in powdery and downy mildew

Summary

Objectives

To determine how, and to what extent, fungicide resistance is developing in powdery mildew, downy mildew and botrytis bunch rot across Australian vineyards

To develop comprehensive information on the fungicide sensitivity and distribution of key pathogens affecting Australian vineyards.

Background

Powdery mildew, downy mildew and botrytis are the three most economically significant diseases in Australian viticulture. Fungicide resistant populations of each disease have already been confirmed in Australia.

The mechanism for how resistance develops and the extent of disease resistance is not fully understood. There are resistant management strategies in place to mitigate resistance potential (e.g. CropLife guidelines contained in the ‘Dog Book’). Further insights into spray practices would confirm whether this approach is actually effective or detrimental.

Prior incidence of fungicide resistance in Botrytis and Plasmopara viticola (downy mildew)in the Australian wine industry has led to the development of laboratory based tests. These have limitations in terms of procedure and turn-around time. This project seeks to improve the robustness of the procedures and make them easier to use. Further to this, the industry does not have access to rapid commercial testing for powdery mildew in Australia.

Research approach

Individual agencies have responsibility for core components of the research and the specific diseases. SARDI has the lead on powdery mildew, NWGIC for downy mildew and Curtin University for botrytis. Testing methods will be shared between research organisations in the event that there are issues sending samples across state borders.

Core components of the project include collection of isolates from the field, phenotyping, genotyping, Next Generation genotypic testing, high-throughput sequencing, resistant strategy modelling and field trials (across SA, NSW and WA).

Industry Benefit

The project will provide industry with an understanding of the extent of fungicide resistance in Australia. It will also provide management packages to efficiently control the three most economically significant grapevine diseases while minimising the risk and hazard of resistance to fungicides. It will improve grower knowledge and maximise effective fungicide choices for best practice disease management programs.