Stripe rust continues to be found in several winter wheat fields mainly in areas that have had rainfall in recent days. Some of these fields have severe stripe rust developing (Figure 1). However, since it has been dry with warm temperatures growers are wondering if a fungicide is still necessary.
Figure 1. Wheat plants with severe stripe rust.
Strip Rust Development: Weather Impact
Stripe rust development, like any other fungal disease, is driven by weather. The favorable weather conditions for stripe rust are cooler temperatures (<65°F) and wet weather (leaf wetness/dew for at least 8 hours). These are the conditions we experienced in the past weeks that have led to high inoculum for this rust.
The current weather conditions though do not favor stripe rust infection. However, because of the heavy inoculum in the area, future favorable conditions could lead to severe stripe rust developing especially in spring wheat. Winter wheat that is at flowering may not benefit from a foliar fungicide to protect against stripe rust. However, scouting should be done for spring wheat and a fungicide planned to protect flag leaf if stripe rust is observed.