I had some green scale, and ants all over some abiu seedlings I have.
I tried a few different times to squish them with my hands, and to apply micro nutritional spays to the trees to get them to grow out of it.
These methods didn't help, and I'm not one to spray pesticides...so the scale got worse.
A week ago, when I was fiddling around with my new hose attachment. It has a setting (one of about 6) called "Flat". Its not as harsh as nozzle, or full, but its more powerful than mist.
I held the leaves and stems of the abiu, and proceeded to spray them off, like pressure cleaning, with the hose. After about 5 min, I had reduced the scale infestation to about 10%. I repeat this method as much as I can (every 3 days, or more if possible). The end result is the ants moving away, and the scale not being able to get a footing on your leaves, which are subjected to blasts of water every 3 days.
The leaves (even the young tender ones) don't seem to mind so much, and only show minimal signs of wear and tear. The hardest scales to get, are the ones along the main nerve of the leaves, near the base...especially the smaller scales. but repeated trauma does them in...trust me....keep spraying religiously for a few weeks (about 3) and it will whoop that scale and ants behinds!
Now go get em!