I have had what appears to be a cure for a couple of years now. The trees can reinfect after a couple of years if you do not preventatively treat the trees annually thereafter, but you can re-cure the tree if it gets sick again. You can give it to healthy trees and they seem to resist sickness and leaf miners. It is a root adjuvant drench with non-toxic agents which lets the plant take up nutrients more easily while helping it kill off the bacteria. I won't be more definitive because it works in my Texas soil, but I cannot say what would happen in other soils besides my heavy clay.
The adjuvant solution has cured fire blight in a couple of fruit trees and I suspect it would also work against the bacterial olive blight affecting Europe. My next planned test however is fig mosaic virus. The adjuvant has never been tested against an incurable virus, so I am quite curious. I now have two infected fig trees to work with, one a mission fig, and the other a Celeste. If I'm still kicking, I will test once Spring comes around.
I have something that is relatively cheap and easy to make, but politicians are giving tens of millions of dollars to a select few universities to do research on genetic splicing, root grafting, and predatory wasps as possible solutions. Sounds like an expensive solution just to let people not lose a portion of their food supply.
Frankly I am pretty disgusted at the agriculture industry right now. It all is about big business and making big money, but while politicians and researchers fiddle, the trees die and burn.