Leaf rust was found in Crop performance test (CPT) plots in Tripp and Brookings Counties. Generally, leaf rust was observed at a low severity, however, two lines in the CPT had severe levels (Figure 1). Leaf rust pathogen, Puccunia triticina, does not overwinter in South Dakota and spores are blown from southern states.
Figure 1. Leaf rust pustules on a flag leaf in winter wheat.
Powdery mildew was another disease found in winter wheat. This disease was mainly observed in the lower leaves (Figure 2). Powdery mildew pathogen, Blumeria graminis, survives on wheat stubble and infection is encouraged by high humidity and warm temperatures.
Figure 2. Winter wheat plants with powdery mildew on the lower leaves.
Fusarium Head Blight (FHB)
Fusarium head blight (FHB or scab) has started to develop in winter wheat (Figure 3). Although the risk for FHB had been low when winter wheat was flowering, the recent rains and warm temperatures favor FHB development.
Figure 3. Fusarium head blight starting to develop in winter wheat.
Most of the winter wheat is past flowering, which is the last growth stage to apply a fungicide. Diseases developing at this point in winter wheat may have minimal impact on grain yield since winter wheat is further along.