Geoff Thomas from DAFWA describes wheat powdery mildew including factors influencing the survival of the pathogen, wheat varieties susceptible to the powdery mildew and fungicide management.
Weather conditions in the WA Northern wheat belt this year have been favourable to the spread of wheat powdery mildew in WA.
Trial results have shown varied responses to fungicide treatments. Significant reduction in disease severity can be achieved by fungicide application however significant yield responses are not guaranteed. Yield responses varied from <5% to 15-17% from single spray applications.
WARNING: Given barley powdery mildew exhibits resistance to some DMI fungicides, it is important to follow good resistance management strategies for fungicides to limit the possibility of this occurring in wheat powdery mildew.
- Know the susceptibility of your wheat variety to powdery mildew.
- Monitor susceptible varieties, particularly in crops which:
- are early sown (exposed to favourable conditions for longer);
- have dense canopies (higher canopy humidity);
- have high nitrogen status (lush plants & higher canopy humidity);
- have good soil moisture profile (higher canopy humidity).
- Fungicides are more efficient as protectants than eradicants, so apply before the disease becomes severe (less than 5% infection in MSS or lower varieties or before canopy becomes too thick or infection progresses to flag leaf and heads). However, weather conditions strongly influence disease developments. Warm drying conditions in Spring can limit disease development and reduce the need for fungicide or reduce the response to fungicide.
KEY MESSAGE: Monitor plants early, keep an eye on the weather and if you are going to spray, don’t spray too late as it may not have the desired effect.