Catey, we really need to see pictures. No one can responsibly recommend any kind of treatment or care until an identification can be made. You might have to clip an affected branch to be able to take a good picture of it.

The Bayer products should never, ever be used unless you know what the problem is. Their use can be very counterproductive.

It is interesting to note that the three plants you've mentioned are notorious for problems. :-(

cateyanne, I do not believe that lichens are harmful.
I do not believe that 'Spanish Moss' is harmful either.
But I have seen many associations of the latter with bare and insect damaged limbs of oaks.
Enough to wonder if what is happening to your plants might be an association of the "harmless" lichen with a harmful agent.
I would be tempted to remove the lichen on one part of an affected tree and observe whether there is improvement.
You will find this interesting.
There is the possibility that something else is causing the decline of the plants in your landscape.
In that case it will be worth your time to systematically eliminate each. Here might be a good place to start.

Lichens, like many other plants, take many forms. Linked below are some images of them.

Here is a link that might be useful: images of lichens

some people pay to have lichens applied to bonsai .. they are not harm full in any sense ...

as noted .... NEVER use a chemical.. w/o a full ID .. otherwise its pollution ... this stuff is actually on the outside of dead bark.. a systemic applied to the plant would never touch it ....

MOST plants.. especially shrubs and trees.. are nudey inside ... just walk thru any forest ... there is nothing to do .. to overcome this natural proclivity ....

ken

I will try to post pics. ronalawn, that is a very helpful article, thank you.

Contrary to what some people appear to believe about lichens and trees and that lichens harm trees, they do not.

Here is a link that might be useful: About Lichens

not sure if its the same problem but it sounds like it on my lilac too. it happens toward the end of summer. It always seems to happen if we go from drought to rain. I never paid it any attention since it was at the end of the year. It did look like grey mold and the leaves would curl up.

Ronalawn, it is very easy to associate a heavy growth of lichen and/or Spanish moss with plant problems, isn't it? It seems to proliferate on declining trees and shrubs. I've had quite a time, over many years, convincing clients that the decline came before the other.

I've always considered a heavy crop of lichen to be a yellow flag...a warning that a plant just might be less than vigorous. The increased air circulation and sunlight penetration have a great deal to do with it. Lichen and SM both benefit from that.

I have seen heavy growths of both cause secondary issues for their hosts. Lichen can become so dense that it blocks lenticels and causes the accumulation of moisture and debris, which on smaller limbs can be a problem. And then can come the real problems.

I believe very strongly that the association between harmless lichens and harmful pathogens does exist and probably more commonly than suggested in kimmsr 's link. It is far more apt to be an issue in warm climates.

The plants mentioned by cateyanne tend to be prone to their own problems and I'm not at all surprised that a little lichen found a good home amongst them.

So botanists and horticulturists that have spent years studying plan growth, plant diseases, all things plant related, do not know what they are talking about?