Powdery mildew in wheat
- Esperance region
James Bee (Elders) has recently reported finding powdery mildew on Scepter wheat near Mailalup. The crop was at the booting growth stage.
Quenten Knight (Agronomy Focus) has found low levels of powdery mildew in Scepter wheat near Neridup. The crop was at stem elongation. The wheat was spader seeded with no in-furrow fungicide applied at seeding. The crop was going to be sprayed with a foliar fungicide.
Quenten has also reported finding moderate to severe infection of wheat powdery mildew in a booting Scepter wheat near Beaumont. He observed that the infection was worse on lighter textured sandy soils with low potassium levels. The crop hadn’t received any foliar or in furrow fungicide when the report was made.
Plant pathologist Andrea Hills (DPIRD) reports that powdery mildew is starting to generally appear in Scepter wheat crops in the Esperance region and growers are applying fungicide to manage it.
Powdery mildew has distinctive symptoms. Fluffy, white powdery growths (becoming cream-grey with age) of fungal spores can be seen on leaf surfaces and stems. Under severe pressure later in the season, mildew can move into the heads.
It is crucial to control powdery mildew in wheat before it becomes too severe and develops in the upper canopy and on heads, as then it is very difficult to control. A registered foliar fungicide can reduce the disease impact, but growers need to consider the weather outlook, variety susceptibility, growth stage and crop yield potential when deciding whether an economic response to fungicide application is likely. Flutriafol at sowing (Hiload, Impact, Jubilee etc) is very effective in preventing early build up in risk prone environments where Scepter is grown.
The wheat variety Scepter is susceptible to very susceptible (SVS) to powdery mildew. For more variety disease ratings refer to the department's 2020 WA Crop Sowing Guide - Wheat.
If wheat powdery mildew is present and increasing in the canopy and the weather outlook is favorable (humid and mild), it is recommended that growers intervene with a well-timed application of registered foliar fungicide in susceptible varieties to stop disease reaching damaging levels and moving onto the flag leaf and head. For more information refer to the department’s Registered foliar fungicides for cereals in Western Australia page.
Managing fungicide resistance
If you suspect fungicide resistance in your paddock then researchers at the Centre for Crop and Disease Management (CCDM) would love to hear from you. To get in touch please email firstname.lastname@example.org or email@example.com . Alternatively, in Esperance Port Zone, sampling for resistance can be arranged with Andrea Hills (048 575 091) or King Yin Lui (0472 848 519).
For more information on diagnosing and managing this disease refer to DPIRD’s Managing powdery mildew in wheat page.
To read about previous powdery mildew this season refer to the 2020 PestFax Issue 10 Barley powdery mildew article.
For more information contact Plant pathologists Kithsiri Jayasena, Albany on +61 (0)8 9892 8477, Geoff Thomas, South Perth on +61 (0)8 9368 3262 or Andrea Hills, Esperance on +61 (0)8 9083 1144 or Ciara Beard, Geraldton on +61 (0)8 9956 8504.
Article authors: Cindy Webster (Narrogin DPIRD) and Andrea Hills (Esperance DPIRD).