Banana tree problems
What is this on my banana tree leaves underside? Is it eggs? Is it fungus? How to treat?
It appears to be egg clusters from an insect. Not sure which.
The insect may or may not be a pest; it could be just using the banana for reproductive habitat without feeding on the plant.
You can inspect daily and determine if the eggs hatch and what kind of larvae they are and if they begin feeding on the plant, or not.
Of if you want to take preventive action without the wait and see approach, you can wipe them off with a rag or cotton glove on your hand, or try washing them off with a hard spray of water, or smother with a horticultural "summer oil" or 70% neem oil. (The stronger concentration of oil used as "dormant oil" will burn the banana leaves.)
Here's a couple of examples: https://www.domyown.com/monterey-70-neem-oil-p-2841.html