Powdery mildew is an unusual disease because it is favored by dry conditions. For example, it regularly shows up in the winter nursery in Arizona, where it virtually never rains. Powdery mildew is always a bigger problem in dry climatic cycles. Dew and moisture in the lower canopy followed by warm sunny days cause the disease to develop very rapidly in July. The earlier the disease shows up, the higher the potential for economic loss.
Good resistance is available, but few breeders have used it so far.
The yellow pea varieties Highlight and AC Tamor are the only two available. This situation will change over the next few years when a new slate of resistant varieties becomes available from several breeding programs. Dry Bean Regional and registration yield trials conducted throughout Saskatchewan in the past 4 years clearly indicate that the best regions of adaptation for dry bean are the irrigation districts around Lake Diefenbaker, and the Black soil zone. The Moist Dark Brown soil zone is suitable in years when it rains in late July or early August. In the Moist Black soil zone, dry bean crops can be grown in years with above average temperature and if a killing frost does not occur before mid-September.