That's BS, organic orchards that have never seen glyphosate are affected too. Uncle Matt's Organic lost one third of its production last year to citrus greening and had to import organic oranges from Mexico to complement its production and fill its contracts. Some major organic associations are already working to fight the disease that affects non-glyphosate users. Tree farming is intensive farming, a good balanced organic soil helps with plant health, but it can only do so much. When trees suffer a thousand cuts during pruning, are shaken to harvest the fruits, all come from a few (or single, like the banana) plant grafted or planted a million times, there are lots of opportunities for diseases to spread. Add to that a global disease to which local trees have no natural defenses, you can see how it does not make a difference to a bacteria or a fungus if its food is organic or conventional. Maybe it will even target organics first, since they taste better! ;)

GMOs are not the only answer to such diseases, but they make even more sense for orchards than conventional selection, which takes decades for trees, and because of the long term investment of such orchards, compared to crops that are planted and harvested within a few months. Plus, it would be an opportunity for biotech companies to show they can do something useful for once: They are often accused to engineer plants with genes that don't increase yield directly or tolerate droughts, all important modern concerns, even if critics focus mostly on glyphosate and not much on Bt traits.

Even on annual crops, GMOs could make a positive difference: African wheat farmers don't have access to expensive pesticides, so a wheat resistant to rust would save thousands of lives. Crossing the variety of wheat they grow with a rust-resistant wheat would work too, but this would introduce half of the foreign wheat's genome, not just the rust-resistance trait, and it would take many generations to regress the undesired traits to keep only its rust-resistance trait, which is an unfeasible task anyway. That would work for organic farming too for me, but I don't see this happening soon, organic farming proponents are too opposed to GMOs, Monsanto made it easy for people to hate them...