As a preventive measure, you can apply fungicides before and as the leaf buds open and expand in early spring. The best fungicide products contain chlorothalonil and triadimefon. You also need to be on the lookout for azalea lace bugs. The adults are inch long with transparent wings that are held flat on the back. Their wings are lacy, with two grayish-brown cross bands connected in the middle.
Nymphs are mostly black and spiny.
The flask-shaped eggs are partially embedded in leaf tissue and often are covered with a black tarlike excretion. They feed on the underside of the leaves. The upper surface of the leaves will have a yellow or white-speckled appearance. The sunnier the location, the more likely azaleas are to have lace bugs. If sprays are warranted, use insecticidal soaps or a systemic insecticide for control.