Fungicide resistance risk
At the time of writing (July 2022) there were no reports of fungicide resistance in wheat powdery mildew in Western Australia. However, in eastern Australia, resistance to both group 3 (DMI) and group 11 (QoI) fungicides has been reported, indicating a significant risk of similar developments in WA at some stage. Adherence to fungicide resistance management guidelines is vital to appropriately manage the disease and prolong the use of registered fungicides, see the AFREN management guide for more information.
Growers and consultants that suspect fungicide resistance to powdery mildew is occurring in a crop can contact the Centre for Crop and Disease Management, Fungicide Resistance Group, at frg@curtin.edu.au to request further information. The CCDM team uses samples to assist with fungicide resistance research.
Poor disease control after fungicide application
Difficulties in controlling the disease observed in the field are unlikely to be the result of fungicide resistance but more likely related to high inoculum pressure, suitability of weather for infection, variety susceptibility, poor canopy penetration, inadequate fungicide rate or use of an outdated product. To avoid development of fungicide resistance follow these recommendations;
- Where possible use fungicide mixtures that contain different modes of action
- Spray fungicides at first sight of symptoms if weather conditions are conducive to persistence and control the disease as early as practical.
- Always use recommended fungicide label rates and rotate the fungicide active ingredients that you use - avoid using the same fungicide, or the same mode of action e.g. DeMethylation Inhibitor (DMI) fungicides, application after application.
- Rotate wheat crops with non-host crops such as canola, barley or legumes.
- Keep crops healthy, but avoid over application of nitrogen as that may increase powdery mildew risk.
Acknowledgments and disclaimer
The information presented here includes DPIRD generated results from GRDC co-funded projects DAW00229 & DAW1907-001RTX, R4R funded Boosting Grains R&D project FFPjP09 and work in collaboration with industry providers ((2015 research results with Landmark, Imtrade, Liebe Group and Northampton Agri Services).
Mention of trade names does not imply endorsement or preference of any company’s product by Department of Primary Industries and Regional Development. Any omission of a trade name is unintentional. Recommendations are current at the time of publication.