Figure 1. Leaf rust developing in winter wheat in Clay County.
Leaf rust was observed in a few winter wheat fields at low levels (Figure 1). Most of the winter wheat is now flowering or past flowering and therefore a fungicide treatment may not be beneficial this time for leaf rust. For fields that were sprayed for stripe rust or other fungal pathogens, leaf rust may not develop to reach high levels to cause significant yield loss.
Leaf Rust: Disease Profile
Leaf rust can be differentiated from stripe rust by the color and the arrangement of pustules on the leaves. Leaf rust has orange-brown pustules that are randomly distributed on the leaf, whereas stripe rust has yellow pustules arranged in a linear fashion on the leaf. The two rusts require different weather conditions to develop. Stripe rust prefers wet and cooler weather, which is the reason we have seen this rust develop this season in parts of the state. Leaf rust, on the other hand, is favored by wet and warmer weather, which is partly the reason why leaf rust shows up later in the season.
Fusarium Head Blight (Scab): Risk Update
The Fusarium head blight (FHB) risk prediction tool for the week of June 12 is showing low risk for FHB throughout the state (Figure 2). This is due to the dry weather in the past days. Scab is promoted by wet and warm weather at flowering time. Although several areas received rainfall, the model uses relative humidity 15 days prior to flowering to determine the risk. Therefore, one or two days of rainfall with several days of unfavorable weather before or after the rain event would still indicate low risk for scab.
Figure 2. Fusarium head blight risk (scab) prediction as on 6/13/2017. Green indicates low FHB risk.