Cereals: Wheat: Powdery Mildew (Erysiphe graminis f. sp. tritici)

Excerpt from Chapter 5, Field Crop Protection Guide, Order this publication

Table of Contents

1. Integrated Pest Management Options
   • Seed Treatment
• triadimenol – Baytan 30
• Foliar Treatment
• propiconazole – Tilt 250 E, Bumper 418 EC
• pyraclostrobin – Headline EC
• tebuconazole – Folicur 432 F
• trifloxystrobin + propiconazole – Stratego 250 EC
2. Related links...

Integrated Pest Management Options

The fungus is very susceptible to weather conditions that promote drying of the crop environment, such as hot, dry sunny weather. Management includes the use of tolerant varieties, crop rotation, tillage, and fungicides.

See OMAFRA Publication 811, Agronomy Guide for Field Crops, for thresholds and more information

Seed Treatment

Comments
Use higher rate for winter wheat. Must be diluted with water prior to treatment of seed to ensure uniform coverage. Treated seed will sometimes emerge more slowly than untreated seed. Avoid late seeding of winter cereals. Do not graze or feed livestock on treated areas for 40 days after planting.

Foliar Treatment

Foliar fungicide applications may be necessary when disease levels will result in yield losses and a susceptible variety is used. Thresholds for fungicide applications differ depending on the age of the crop. Early-season powdery mildew control is warranted when 5%-10% of the lower leaves are infected, which may limit later infection. Later in the season, powdery mildew symptoms on the flag leaf (1% of leaf) and the second leaf (3%-5% of the leaf) require immediate attention, especially if prolonged wet, humid weather is forecast.

See Appendix G, on page 85, for Zadok's cereal growth stages

Comments
Ground and aerial application. Apply at early signs of disease from the beginning of stem elongation (Zadok's 29-37). If conditions favourable to disease continue, another application will be necessary. A second spray may be applied before head is half emerged (Zadok's 49-55). Can be tank-mixed with several cereal herbicides. 45 days to harvest.

Comments
Ground or aerial. Apply only up to flag leaf fully emerged stage (Zadoks 39). Do not apply at boot stage (Zadoks 47) and beyond. Maximum 2 applications per season. Tank-mixing with insecticide is not recommended, as this fungicide could affect insecticide efficacy.

Comments
Ground or aerial application. Only one application per year. Apply only up to flag leaf fully emerged stage (Zadok's 39). Do not apply at boot stage (Zadok's 47) and beyond. Use non-ionic surfactant such as Agral 90 or Agsurf at 0.125% vol/vol. 36 days to harvest.

Before using Folicur for wheat leaf diseases, consider that Folicur can only be applied once per year and has been traditionally used for Fusarium control.

Comments
Ground and aerial application. Maximum of 2 applications per year. Do not apply the second application within 14 days of the first. Apply only up to flag leaf fully emerged stage (Zadok's 39). Do not apply at boot stage (Zadok's 47) and beyond. Can be tankmixed with Buctril M in wheat. 45 days to harvest.

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Related links...

• Agronomy Guide for Field Crops - Publication 811
  • Cereals: Powdery Mildew
• Diseases
• Cereals
• Appendix G: Cereal Growth Stages

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