Stem rust pustules usually are considerably larger than those of leaf rust. Stem rust urediniospores seldom germinate below 55 o F. Early-maturing winter wheat varieties usually escape stem rust infections. Pustules in a stripe-like arrangement with yellow colored spores. Stripe rust can be a severe disease in cool moist climates. Usually, only trace amounts occur in Oklahoma.
Powdery mildew occurs to some extent every year.
There is considerable varietal difference in susceptibility to this disease. The prevalence and severity of powdery mildew increase when large acreages of the more susceptible varieties are grown. Powdery mildew, as seen in a scanning electron microscope. Tuftsspeckled with the small black fruiting bodies called cleistothecia, the overwintering stage of the fungus. The fungus overwinters as cleistothecia in wheat crop residue from the previous season.