Maximizing value with wheat fungicides

By Kirsten Grant
Crop Sales Specialist
AGRIS Co-operative - Brigden

Many wheat crops are off to a good start this year. Our goal is to help you maintain your yield potential and limit the risk of loss to crop disease.

Risks

Fusarium head blight is a severe infection that can cause yield loss of up to 50% and a significant reduction in grain quality, costing you at harvest.

Wheat can also be susceptible to various leaf diseases, including powdery mildew, rust and Septoria leaf spot. If left untreated under favourable conditions, these diseases can lead to shrivelled seeds, lower test weights and yield loss.

Favourable environmental conditions

Fusarium head blight thrives under warm and wet conditions, particularly during the flowering to soft dough stages.

Prolonged cool, cloudy, and wet weather favours the development of leaf diseases like powdery mildew and septoria. Favourable environmental conditions do not mean a fungicide application is immediately warranted. These conditions remind us to scout early and often to look for signs of disease pressure.

Many wheat stands this year are quite dense, leading to poor drying conditions. Target scouting these thicker wheat stands for early signs of leaf disease.

Signs of disease pressure

Wheat infected with fusarium head blight has florets that darken and become oily in appearance. Large tan or brown lesions can affect the entire spikelet or a large section of the wheat head. The grain often has a white, chalky appearance.

Septoria presents itself as oval or elongated spots or lesions. The centre of the lesions often become pale with many small black dots.

Powdery mildew appears as white or pale grey fuzzy colonies on leaves. Colonies are on the leaf surface only and can be brushed off with your finger.

Leaf rust shows up as similar small round or oval spores that are orange to light brown and stay on the upper surface of the leaf.

Photo above: Leaf Rust.

Photos: OMAFRA Publication 811.

Fungicide application

In some cases, T1 fungicides may not have been applied as planned as weather conditions and cool night temperatures kept us from tank mixing and applying with herbicides. If you notice disease pressure where a T1 fungicide was not applied, a T2 fungicide is an option. A T2 fungicide will help protect the flag leaf from leaf disease pressure moving up the plant from affected lower leaves.

The T3 fungicide application is important for protecting against fusarium head blight, but it also protects against septoria, powdery mildew and rust in late stages of development.

Timing the T3 fungicide application starts with scouting your fields. Timing of the T3 fungicide application is critical. The latest time to start scouting is at Day 0 or Zadoks 59 (head clearing the ligule). The optimal timing for application is early flowering stage, between Day +2 and Day +4.

It’s unlikely that the entire wheat field will be at the same stage. When the anthers are out in the middle of the wheat head, on 75% of the heads in the field, it is time to apply. If weather conditions are not ideal for spraying, your fungicide will have more value if applied slightly earlier rather than slightly later.

When spraying, the goal is to maximize coverage. It is important to spray with 20 gals/acre of water with forward and backward tips.

With current wheat prices, our goal is to maintain your yield potential. Speak with your local AGRIS or Wanstead crop sales specialist about available wheat fungicide options.