There are several approaches to management of azalea flower blight. When the blooms begin to open, apply a fungicide containing Bayleton, or chlorothalonil, according to label directions. Fungicides containing either of these active ingredients are available under several trade names at most garden supply stores. The time is approaching to declare war on another disease which affects azaleas. Leaf gall, which shows up later in the spring following bloom, is also caused by a fungus.
Infected leaves become fleshy and severely distorted.
As the galls form, affected parts may become whitish or light green. Sometimes a fleshy rosette of leaves appears at the tip of a branch, or a gall becomes bladder-like as it decays and dries out. Leaf gall reduces the ability of azaleas to produce flowers the following spring, since heavily diseased plants lose many of their leaves needed for food manufacture. Azaleas are most susceptible to leaf gall when young leaves appear, and like flower blight, is most severe following periods of rainy weather. Infection cycles occur as long as young leaves are present on plants.