Wheat Disease Update: May 19
Recently, many parts of Nebraska received varying amounts of much needed rainfall. However, dry conditions prevailed early in the wheat growing season. These drought-like conditions slowed the onset of diseases in wheat fields.
In a grower’s field in Jefferson County in southeast Nebraska on May 19, only trace levels of disease were observed, with the field looking luxuriant green (Figure 1). Wheat in this field was just starting to flower (Figure 2). Diseases observed at trace levels included wheat streak mosaic on isolated plants (Figure 3), fungal leaf spots, and barley yellow dwarf.
At the Havelock Farm in Lincoln (Lancaster County) on May 18, diseases were similarly at trace levels. The most notable diseases were fungal leaf spots (Figure 4) and barley yellow dwarf (Figure 5).
Fusarium Head Blight
Wheat in the eastern half of the state is heading or starting to flower. It is at the flowering growth stage that the Fusarium head blight fungus infects wheat heads. Currently (May 20), the Fusarium risk tool is showing a low risk for Nebraska. However, localized rainfall can increase the risk for Fusarium head blight in individual fields. If your wheat is headed or flowering and your area recently received heavy rainfall and/or rain is in the forecast, consider your wheat field to be at an elevated risk.
Management strategies for Fusarium head blight include planting moderately resistant varieties and application of a fungicide at the early flowering growth stage. Fungicides that have good efficacy on Fusarium head blight include Miravis Ace, Prosaro Pro, and Sphaerex. These fungicides are also highly effective in controlling foliar fungal diseases.
Stripe Rust and Leaf Rust
Monitor reports from southern states. The last report from Kansas on May 9 indicated that none of the three rust diseases (stripe, leaf, and stem rust) had been observed in the state. The possibility remains that we may see stripe and leaf rust in Nebraska. If we do, it is likely to be later in the growing season and the prevalence, incidence and severity will depend on the weather, with drier conditions limiting and wetter conditions favoring disease development.
Rust diseases are controlled with variety resistance and fungicide application timed to protect the flag leaf. If your wheat is headed or flowering and your field is at an elevated risk for Fusarium head blight, one application of a Fusarium head blight fungicide will also effectively protect the crop from rust and leaf spot diseases.