Thanks for the most useful reply! The site looks very helpful too.

Stephen Henning wrote:


Yes, there is a chance they will come back. Loss of leaves are a
symptom of a problem, not death. If the buds are still alive, then the
plant should produce flowers and new growth.

The most common fungal disease of the leaves is powdery mildew. A
grayish white, powdery coating or fuzzy white growth on upper or lower
surfaces is azalea powdery mildew (Microsphaera azaleae). This is more
prevalent on deciduous azaleas and sometimes it affects the lower
surface more. Entire leaves can be covered. In late summer and fall,
small black specks may be found in the white areas. Powdery mildew is
more severe on shaded plants. It is favored by the high humidity found
in crowded plantings and damp locations. There are a number of ways to
manage this disease.

€ Do not overwater or overfertilize plants, as the fungus prefers
succulent new growth.
€ Hand-pick and destroy mildewed leaves to control small amounts of
infection.
€ Hose diseased plants with water when practical. This can help remove
fungus and prevent new infections.
€ Prune and space plantings to allow good air circulation. Do not plant
in extremely shaded or damp areas.
€ Rake and destroy fallen leaves year-round to reduce infection source.
Do not compost diseased materials.

Chemical control is possible. Begin applications when you first notice
the disease on current-year leaves. If disease appears late summer,
applications are not necessary on deciduous azaleas. Do not apply sulfur
products when temperature is over 85F or within a few weeks of an oil
spray.

Black Leaf Sulfur Dust
Bonide Lime Sulfur Spray
Bonide Remedy
Monterey Fungi-Fighter
Ortho RosePride Funginex
Ortho RosePride Orthenex
Safer Flower, Fruit & Veg Garden Fungicide
Spectracide IMMUNOX

This fungal disease can weaken the plant. Spray when you first see the
disease and then again in 10 days. Chemicals will not control the fungi
that has already become established. For more information see the
section following on 'rhododendron powdery mildew'. The symptoms are
different, but the organism and control are the same.