Here is a photo of one of the ones that is about 50% dead. You can see there is still new growth coming in at the base of the branches. On this one should we prune out all of the dead branches?

I can only guess...but I'd say they died of wanting a drink. It's just an obvious guess and may be quite wrong...remote diagnosis is a bit hard ;)

That did cross our mind, however it was a pretty wet spring here in NY and we didn't notice them drooping. Also all 6 of the shrubs are in the same location, so we thought if it was a water issue they all would have suffered the same fate. But we are new to this so we could be totally wrong!

If the root balls were not teased apart when planted, they may have dried out so completely that they could not absorb water no matter how rainy the weather. This is a common occurence because of the peat based planting medium and sometimes happens even with careful attention to the root ball when planting.

Dig up and check. If the root ball is totally dry, tease apart, soak in water for 30 minutes or so, then replant. Keep watered - when needed - with just a trickle at the base of the plant for the rest of the summer and fall. Cut out any obviously dead wood.

A fungal infection of the roots is possible, but doesn't seem very likely since new growth is appearing.

Okay, thanks. We'll give it a shot and report back.

My mother's neighbor's azaleas started dying about 2years ago. Last year, this spread to my mother's plants. They have been in the garden for most of the almost 50 years she has lived in the house.
Now, my azaleas are also dying. They have been in the side garden for the 17 years I have owned this house, and were probably here many long years before (the house was built in 1902).
So, something IS going on here in NY. But, what??

We have never overwatered, etc...
These plants have thrived for a long time and were happy in their placements.
I have read of azaleas being left in wills in Japan;some specimens are hundreds of years old. This dye back is very disturbing.
Has anyone heard of any disease or virus?Like the virus that was killing impatiens up here?

Your best bet would be to contact your County Extension Service, State Agriculture Department. or a nearby university for help. There are some fungus diseases that can cause this kind of fairly sudden decline, but determining if this is the cause and exactly which pathogen is involved usually requires laboratory analysis. Not sure where you are in NY, but Cornell is extensively involved in this kind of work.

JemJazzington:
Perhaps it only seemed like something that "spread". Many, not all, but many instances of azalea dying in NY this year can be traced to the hard winter we just had. Granted, mine were all newly planted last summer, but of 6, I had one completely die (no leaves in spring), one looked dead but eventually sprouted leaves, and one seemed fine but died after growing new leaves for a couple months Of course, there are many other causes possible, but this was really such an unusually hard winter for NY and the NE as everyone has been saying. Good luck!

We dug up three of the six azaleas today -- the two that look completely dead and the one that's about 50%. I am not sure what the roots are supposed to look like, but on all three plants the roots looked as though they were bound together in the shape of a pot (see photo). Does this mean they were rootbound?

I used a knife to tear apart the roots as much as I could as they were quite tough and difficult to pull apart, and soaked for 30 minutes before replanting. I'm not sure if there is any hope for them but I'm keeping my fingers crossed.

The photograph shows a classic example of a rhododendron/azalea that has not had its rootball teased apart before planting. When this happens, the peat based medium in the pot gradually loses moisture and becomes very difficult to rewet. Further, it shrinks, creating a gap between the rootball and the native soil. This makes any capillary transfer of moisture from soil to rootball impossible.

As you discovered, prying apart the roots can be difficult when the rootball is in this condition. You've done all you can and these plants may or may not rejuvenate. Rhododendrons are tough and resilient plants, so the odds are actually pretty good. If the weather turns dry, don't forget to water with just a trickle at the plants' base. This ensures you're directing water to the azalea and not saturating the surrounding soil.

Thanks for the advice, and for helping to diagnose the problem! Two follow-up questions for you:

Should we dig up the three azaleas that only seem to be partially affected, and give them the same treatment?

Also, for the two that look dead, how long do we wait before giving up and replacing them with something else? Would they revive by fall, or do we have to wait until spring?

Yes to digging up the partially affected azaleas. This will do no harm and will insure that they are properly planted.

The second question is a little more difficult. Scrape away a bit of the bark and check for green cambium. If there is none, you might as well replace them now. If you do see green cambium, prune back the clearly dead parts to where the green cambium is evident. They should begin to put out new green growth within a few weeks, perhaps even sooner. This new growth is going to have little time to harden off, so protecting the plants from sun and wind this winter with burlap screens or evergreen boughs is a good idea.

The two worse of the shrubs seemed to have no green cambium whatsoever, so I suppose we'll give up on those.

We digged up the other three azaleas and their roots seemed to be in the same condition as the first three. So we pried the roots apart, soaked, and replanted. I'll report back and let you know if they recover. Thanks again for the advice.

This is good info with pictures. A few years ago, one azalea that was at the house I bought, looked like this. I never knew what could have happened but this is the kind of rootball it had when I finally gave up on it and dug it up to toss it away.

I do know that the home owners had put in some landscaping to try to sell the house, so many of the plants were just put in recently and had not been plants that were established as regular plants around the house. As a result, they looked good and nice in those first few months as they were showcasing the home, but in the long term (even same year), some of those plants perished for similar reasons like this.