Stripe rust - Stripe rust continues to be observed throughout Mississippi as well as Louisiana and Arkansas. At this time I would not say the disease is widespread (at least in MS) but symptoms can clearly be observed in some fields throughout the MS Delta.
Leaf rust - Over the past week leaf rust has been observed in a few Delta wheat fields. Leaf rust differs from stripe rust in that pustules are more scattered, appear larger in size, and sporulation from the pustule will be more orange in color (see attached photo for comparison between leaf and stripe rust). As a plant pathologist I am not near as concerned about leaf rust as I am stripe rust. A similar situation could be stated regarding common rust in corn as compared to southern rust in corn.
Powdery mildew - Powdery mildew can still be observed in some wheat fields in southern MS. In addition, powdery mildew has been detected in the south Delta. More than likely, those fields with observable powdery mildew were exposed to prolonged wet, cool conditions. Scout fields for powdery mildew and keep in mind that in some instances “hot spots” of powdery mildew can be visible from the turn row but can easily be confused with stripe rust, nutrient deficiencies, freeze injury, and herbicide drift/injury. Part the canopy back to observe for powdery mildew. Even though the disease may be present lower in the plant canopy remember that yield loss is dictated by disease being present on the flag leaf. If the flag leaf has emerged and it looks like the disease is going to remain in the lower canopy I don’t suggest you apply a fungicide.