I've never heard of live oaks getting mealy bugs but that doesn't mean it never happens. First I would try and get a positive ID on what you have. If you can take a picture and post it that would be great. Or you can take a sample to the extension office out in Seffner and someone there can help you with an ID. Without a correct ID you're just running in circles.
Hope this helps.

Here are a couple of pictures that I took of one of the lower branches.

http://img.photobucket.com/albums/v12/smg6228/Tree.jpg
http://img.photobucket.com/albums/v12/smg6228/Tree2.jpg

Any help would be most appreciated!

Doing a search I found this...sounds familiar? (see link)

soo...besides the coinsidence of the question and answer:
I think this is what you have: Interior Live Oak Mealybug
BUT I can't find any real information on it. The reason that I think it is this mealybug is through process of elimanation. Nothing else seemed to fit.
I couldn't find out how harmful it is or anything else. I am going to assume that since there is very little information that it isn't much of a problem.
You can try doing a search and maybe find something I didn't.
If no one else steps up to the plate to help you on this forum then you can call the extension office @ 744-5519

Here is a link that might be useful: white stuff

Does it look like this?
john

Here is a link that might be useful: interior live oak mealy bug

Zono supplied a photo but not a close up so we're working with wide angle shot and a close up. it's not easy to make an id.

Kind of an interesting problem in that the U of FL seems to have no records concerning the Live Oak Mealy bug. If that bug had ever been an economic pest in Fl they would have. It was found in 1900. Wooly aphids can be controled with a systemic like imidacloprid. I get them on my orchids and alocasias from time to time, but to treat a live oak...get a 50 gal drum to mix in.

good luck john

Try Bayer Tree and Shrub concentrate . It is a drench that is a systemic containing Imidacloprid labeled to kill aphids and scale among other things . Read and follow the directions on the label carefully . This contains no fertilizer and can be used at any time .
Not cheap but well worth it when you have identifiable problems . Easy to use too .

You may have a bark lice. They are no big deal - they are absolutely harmless to the tree. They appear every August and September and cover the main trunk, major and minor branches in a heavy white webbing. See link below.

Here is a link that might be useful: Bark lice

Here is link with pictures of every bug that ever infested any tree. I don't think I'm exagerating.

Here is a link that might be useful: Bugs rogues gallery

Hi zonitrichia- did you ever positively identify the issue with your live oak and a treatment to resolve the problem? I think we

have the same issue and hoping you can share what happened with your problem. thank you!

I just moved into a new place. I transplanted plants from old garden to new one. My neigh has a tree with branches hanging over fence. No problem gives plants a little shade. Until I noticed that my plants had black soot all over the leaves. I looked up and the tree is infested with white mealy bugs. They stuck the sap from leaves and the excrement left behind is this horrible black stuff on my plants. In articles it says you can spray with isopropyl alcohol mixed with water. It's a large tree so I'll have to use a special sprayer. Has anyone tried this? I dont like pesticides I have animals so I'll try this next year.