Looks a lot more like insect damage than any fungal issue but would need a clearer, close-up photo to assess properly. Also the possibility of a viral issue but this looks like it is focused on new growth, which is much more suspect of insect problems. Any stickiness noted?

It is not a simple matter of prescribing a "pest control spray" for fruit trees. One needs to know exactly what the problem to be treated is before being able to make any recommendations. Often a dormant spray of horticultural oil can be useful for insect control but is unnecessary unless a problem really does exist. It is never a good idea to spray without a specific intent.

Ants tend not be an issue in my area so I'll let someone else speak to that. Baiting with borax is all that is ever really necessary here.

Citrus leafminer

Info here
http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn74137.html

Here is a link that might be useful: citrus leafminer at UC

Lots of info also in Citrus Forum
http://forums.gardenweb.com/forums/citrus/

Here is a link that might be useful: Citrus Forum

if its only one branch.. and thats all the pic shows ....and i dont care what plant it is .....

properly prune off the branch.. and be done with it ...

99% of the time.. problem solved ...

ken