If azaleas have developed small, white cheesy blobs on the shoots or leaves, this is azalea gall, a common disease of both deciduous and evergreen species. The tender indoor varieties are particularly prone to it, especially when they are grown in greenhouses. If you look closely at the blobs or swellings, you will see that they are covered with a white, powdery coating. This is made up of the spores of the fungus which causes the disease. There is no reliable fungicidal treatment, and affected plants soon lose their vigour.
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The best antidote for azalea gall disease is to watch for any signs of an attack and then carefully cut off the infected shoots and burn them. Avoid spreading the disease by dipping your knife or secateurs into disinfectant between cuts and by taking care that you do not disturb the spores