Irregular brown spots appear along the leaf margin, rapidly enlarge into irregular brown to black blotches, and advance toward the mid-vein until the leaf dies. Blighted leaves usually cling to diseased shoots. Blighting of the foliage usually starts on leaves closest to the soil like and spreads towards the shoot tips. Irrigate azalea container stock and liners at mid-day to reduce the time the foliage remains wet. Spacing out container stock to improve air circulation can reduce the spread of this disease.
Fungicides provide good protection from web blight.
A fungicide application is also recommended prior to the winter storage of azaleas under protective plastic cover. Small pustules producing masses of yellow to orange spores develop on the lower leaf surfaces in late summer or early fall. On susceptible azaleas, these pustules cover virtually the entire lower leaf surfaces, which often results in early and heavy defoliation. The reaction of deciduous azalea cultivars to rust ranges from resistant to highly susceptible. Cultivars having the best rust resistance are Balzac, Gibraltar, and Red Letter.