Azalea leaf gall. A very common fungal disease that affects the new growth, distorting it and causing it to swell and contort. It is a bit more alarming in appearance than it is actually harmful to the plant. You can spray for it (need to do so before you see any signs) but I prefer to just clip out and destroy the affected portions after the azaleas finish blooming.

IME, its appearance is rather random. Last year I had one azalea that was heavily affected and received a good shearing. This year the plant is perfectly clean.

Azalea Gall. The pods start green and-or pink. Then they get a white-ish color when they release the fungi. You need to prune them off as soon as you see them and throw them away in the trash. Throw away the leaves too. Unfortunately, there are no resistant azalea varieties or a fungicide that you can use.

Another approach may be to interrupt the life cycle of blisters early (by pruning these blisters) and make conditions difficult for fungi, in a way that would not harm the health of azaleas.

What I meant by interrupting the life cycle ... The new bulbs have green or pink colors. After a while, the blisters develop growth similar to white mold, which is when the fungal spores start to spread. So, remove the blisters when they are green and have not released their fungal spores yet. It would take several years to be effective if you have many but, after several years, pruning off the blisters would reduce the number of blisters you get.

To make the environment difficult for fungi: I would increase the sunlight in the area of the affected azaleas (you could for example prune trees or raise their canopy); replace the mulch with a new mulch (the old mulch may have a lot of fungal spores); collect all plant debris a.s.a.p. (leaves, branches, flowers) and throw them in the trash; and consider switching to drip irrigation (this will reduce the humidity of the environment and will not make branches and leaves of azalea wet). When my sprinkler broke, I replaced it with a drip irrigation system to reduce humidity because my hydrangeas had a lot of Cercospora leaf spots. If your soil is often wet or soggy, I would reduce the amount of water a little.

Also, if the azalea plants touch each other, consider trimming to prevent one plant from easily infecting another plant. And just consider a little more cutting to add sunlight inside the dark areas inside the azaleas. Pruning and opening the plant in places provides more sunlight and can also dry out wet parts of plants.

I guess you could call all of these things good sanitation techniques that can help you reduce the blistering problem. They make the environment difficult for fungi.

I have not heard of fungicides that have successfully solved this problem, so I recommend cutting the bulbs and making them as uncomfortable as possible. But this was odd: I visited the website of the Azalea Society of America recently. In one web page on this subject, they simply said there were no effective fungicides. And on another web page, they said to collect the blisters by hand, destroy the affected leaves or try to spray the leaves with one of these products and then determine if they help or not: Bayleton ( a systemic fungicide developed by the company Bayer), Ferbam (a chemical that is often used as a fungicide), Captan (a former systemic fungicide) or a fungicide based on fixed copper. They recommended starting spraying at the end of the flowering period and continuing at 2-3 week intervals until mid-June. So try these sprays to see if they help or not (they may only help to control a bad infestation, not to cure the problem).

There are many fungicides that will treat this issue but the vast majority of all fungicides are prophylactic...they can only prevent the disease taking hold. They will not cure or reverse it, which is why any spraying needs to be done before you see any symptoms.

It is not really a big deal and does not require heroic efforts to control. Just snip off the galls and destroy. Like most early season fungal issues, it is highly weather related.