28 November 2024
A number of regions have reported wet weather over the past few days, resulting in increased risk of downy mildew infection. This eBulletin provides a reminder of strategies to reduce the risk and severity of downy mildew.
Understand your risk
- Know the conditions (temperature, rainfall and time) conducive to triggering a downy mildew infection event. (Refer to this Vitinote on downy mildew characteristics and this fact sheet on managing downy mildew). Monitor the weather or your local ‘crop watch’ service for disease alerts and understand the risk of disease in your region.
- Know what tissue is susceptible at different stages of the season:
- Three to four weeks after fruit set, berries gain resistance to infection and by pea-size (E-L 31) are immune.
- Green tissue remains susceptible to downy mildew (leaves, stems, berry stalks).
- Assess how much vine tissue is uncovered since your last spray.
- Monitor your vineyard for signs of downy mildew. (Refer to this Vitinote on downy mildew characteristics and this fact sheet on managing downy mildew).
- If you are considering application of agrochemicals as part of your management strategy, refer to the ‘Dog book’ for guidance:
- Apply only products registered for downy mildew on grapevines
- Monitor the growth stage of your block(s) using the E-L system to ensure you only apply chemical options appropriate for the current growth stage to minimise the risk of agrochemical residues.
- Adhere to the CropLife Resistance Management Strategy for downy mildew (page 16 ‘Dog book’).
- If you have had a downy mildew infection event and are using a metalaxyl or metalaxyl-M (group 4) for curative control
- apply as soon as possible after an infection event and before the first sign of oil spots
- apply a second group 4 spray seven to ten days after the first application
- always apply group 4 fungicides in mixtures (e.g. with copper)
- IF THE DOWNY MILDEW EVENT OCCURS EARLY ENOUGH IN THE SEASON and assuming sensitivity remains, after applying a group 4 fungicide, use a follow-up fungicide from groups 40, 45, 21, 49 or 11 prior to the next period of infection to ensure control (your options across these chemical groups are reduced later in the season)
- Contact your grape purchaser or winery to discuss options if required.
AWRI is in conversation with a range of chemical companies to understand the current availability of metalaxyl and metalaxyl-M products and will provide further updates on this if needed.
Additional resources
- Control strategies for downy mildew and Botrytis (AWRI webinar recording 9 November 2018)
For more information or assistance, please contact the AWRI helpdesk on 08 8313 6600 or helpdesk@awri.com.au.
This eBulletin is supported by Wine Australia with levies from Australia’s grapegrowers and winemakers and matching funds from the Australian Government. AWRI is a member of the Wine Innovation Cluster in Adelaide, SA.