What Increases the Risk of Infection?
- Cool temperatures
- Prolonged periods of wet weather
- Rust problems in the southern US states and Mexico could mean the same for Ontario as storm systems carry the spores north.
- Planting susceptible varieties
- Planting after another cereal or corn crop
How Do I Know When to Apply a Fungicide?
The higher the price of wheat, the more economical treatment is. In general, if trace amounts of rust, powdery mildew, or leaf spot are present on the flag leaf in the early boot stage of development, and infection below the flag leaf is moderate or moderately severe, it’s highly likely that severe infection of the flag leaf will occur. Applying a fungicide is cost-effective. Fungicides are most effective if applied as a preventive treatment. Application after the flag leaf is already infected, may result in little or no yield increase. Fungicides are well utilized by growers to protect their investment and help increase plant heath and yield.
Leaf Rust, Stripe Rust and Stem Rust
Threshold: 5-10 pustules or 1% of the leaf area is affected and the forecast calls for rainy weather (from Z50-Z69).
- Removing the alternate host (common barberry), will reduce stem rust.
- Use tolerant varieties when possible, and apply a foliar fungicide when the threshold is reached.
- Fungicides to use include: Stratego Pro, Acapela, Headline AMP, Quilt, Trivapro, Propiconazole
Stagonospora Glume Blotch
Threshold: 1-2 lesions on the leaf below the flag leaf up to booting, or 1-2 lesions on the flag leaf at head emergence.
- Rotation with crops other than cereals.
- Plowing down cereal residue and volunteer wheat.
- Fungicide seed treatment or foliar fungicides including: Headline AMP, Prosaro, Propiconazole
Septoria Leaf Spot
Threshold: 1-2 lesions on the leaf below the flag leaf up to booting, or 1-2 lesions on the flag leaf at head emergence.
- Rotation with crops other than cereals.
- Plowing down cereal residue and volunteer wheat.
- Fungicide seed treatment.
- Foliar fungicides including: Stratego Pro, Headline AMP, Acapela, Quilt, Propiconazole
Tan Spot
Threshold: 5-10% of lower leaves affected early in the season, 1% of the flag leaf affected and 3-5% of the second leaf later in the season.
- Include non-host crops such as other cereals, corn, soybeans and alfalfa in the crop rotation.
- Plant resistant varieties.
- Removal of cereal residues through tillage.
- Foliar Fungicides including: Stratego Pro, Headline AMP, Acapela, Quilt, Propiconazole
Powdery Mildew
Threshold: 5-10% of lower leaves affected early in the season, 1% of the flag leaf affected and 3-5% of the second leaf later in the season.
- Plant resistant varieties and crop rotation
- Removal of crop residue through tillage.
- Fungicides include: Stratego Pro, Headline AMP, Acapela, Trivapro, Propiconazole
Barley Yellow Dwarf Virus
Threshold: 5-10% of lower leaves affected early in the season, 1% of the flag leaf affected and 3-5% of the second leaf later in the season.
- Avoid early planting.
- Control cereal aphid populations since it is only transmitted by aphids.
- Utilize an insecticide on heavy aphid populations.
Soil Borne Wheat Mosaic and Wheat Spindle Streak Mosaic
- Plant resistant varieties.
- Improve field drainage.
- Avoid soil compaction.
- Long Rotations with at least 4 years between winter wheat crops.
- Plant later in the fall, when soils are cooler and less favourable for development of the virus.
Additional Sources
OMAFRA , Colorado State University College of Agricultural Sciences