I will be curious to see the answer to this because I had thought that musa and ensete were two different types of plants though related.
I also have never had any aphids on my banana plants though we have plenty of aphid and plenty of bananas. Maybe these are spider mites? Which I have heard of being on bananas.
Anyway, maybe someone with more experience can tell you.

I use a mixture of hand-soap and spiritus in water and spray the plant, ca 10cc (2 tablespoons) of each per liter. It doesn't hurt the plant but the aphids are gone.
Simon

The aphids would not be in the soil, so submerging it won't help. Plus that would be bad for naners, including ensete.
Aphids can be sprayed off with water, repeating frequently.

seahorse