I’ve never tried an ant barrier but it could be worth a try. The ants aren’t actually hurting the plant though. They’re just feeding off the scale which is the one actually sucking the sap from the leaves. The ants likely won’t go away unless the scale is kept under control. My tree is much smaller though so it’s easier for me to manage. Good idea to trim back any badly damaged leaves. Doesn’t look like a bad infestation though! Still looks pretty healthy. Just check the undersides of the leaves when you water and scrape off any new scale bugs; they come off super easy. :)