Banana Blight/Panama Disease.

All bananas are essentially clones as they have no seeds and banana trees are propagated from offshoots.

In the 1950s a fungus caused massive die off of banana trees leading to the effective death of the entire Gros Michel cultivar. We have overcome this set back by introducing the Canvendish cultivar which at the time was resistant to the fungus and was a commercially viable plant.

We now face a resurgence of the fungus which has found a way to infect the Canvendish cultivars. Being clones, they have no way to develop a defense as we can't interbreed the banana plants to produce resistance to the fungus. This time round we don't have a readily replaceable cultivar thats commercially viable if the Canvendish cultivar fails.

https://en.m.wikipedia.org/wiki/Panama_disease

For reference the Gros Michel is still grown on a boutique scale and a 5 lbs box of Gros Michel bananas costs US$127 excluding shipping.