I was told that, because the leaf miners are curled into the leaves, they are difficult to control and -my guess- they are easier to deal with prior to reaching this stage. See if neem oil or permethrin products will get rid of them. Re-apply around May to kill newborns from eggs already deposited.

I have not heard of any real damage other than to the way a plant looks though. Yes, you may end up with some yellowed or dead leaves but I doubt the infestation would affect all the leaves.

I hope someone chimes in with more or newer info.
Luis

And I was waiting for someone with personal experience in azalea leaf miner to answer hudvalley...

I did look up photos earlier of azalea leaf miner damage and didn't find what I expected...the tell tale wiggly, drunken sailor 'paths' that I've seen in my columbine and one clematis...see linked photo. This leaf miner damage wouldn't be described as transparent if it's typical...would you call the entire leaves looking transparent because you may be seeing damage from a sucking insect i.e. lace bug...

Maybe a better description of what you are seeing please?

And the conventional suggestion for leaf miner is to do nothing - they have so many natural enemies just letting the infestation resolve itself is often adequate. Otherwise, a systemic would be required given the upper and lower leaf surface protection the larvae have.

Here is a link that might be useful: {{gwi:400165}}

the leaves retain their shape and no yellowing or curling has occurred despite a dry season. the leaves appear mottled not the dense deep green you would expect on azealas. the "mottle" is clear like the chlorophyl (sp?) is missing. no clear "paths" are visible in the leaves. they bloomed very well in the spring and grew well all summer. thanks!

Without a photo, there could be a few possibilities -

At the risk of being too basic, do you know what chlorosis looks like? Generally lighter leaves than normal but with the leaf veins initially staying darker green - causes soil with too high PH, and anything that could damage roots leading to those remaining being insufficient to 'feed' the shrub (root weevils, nematodes, poor drainage, fertilizer burn)

And several types insect damage could cause change in leaf color that could be described as white, grayish, silver mottling or stippling: lace bug, white fly, spider mites, thrips. Have you noticed any evidence of eggs, frass, or larvae on leaf undersides that might help identify?

You might read through the attached link, problems of leaves

Here is a link that might be useful: Hennings, Problems with Leaves