Banana plants are vulnerable to many common insect pests. Hot, humid climates increase the damage and decay to leaves and fruits that insects begin to feed on
Aphids
Aphids are no bigger than the head of a pin, soft-bodied and can be pale green or brown, depending on their species. They puncture leaves and stems, causing curling, leaf drop and eventually plant death, yet the lightest pressure of your finger will kill them. Look for aphids on the undersides of leaves and along the stems of banana plants and kill them right away. Aphids are easily dislodged by a hard spray of water from a garden hose, and are usually unable to climb back onto the plant once they've been knocked off. Clip off heavily infested leaves, bag them and throw them away.
Thrips
Anthurium, rust, rind and banded greenhouse thrips attack banana plant leaves, stems and fruits. They are tiny, usually a millimeter or less in length. Their mouth parts puncture leaves and stems, sucking out juices and causing lesions, curling, decay and death. Leaf symptoms usually appear during hot, dry weather. Look for curling leaves, and dark, v-shaped markings on leaf stems. Damaged leaves will eventually turn bronze or rust-colored. Try spraying with a solution of soapy water to deter thrips before moving to an insecticide containing imadocloprid.
For chemical treatment try low toxicity products such as Imidacloprid, Acitamiprid, Thiomethoxam etc.
Save your plants first. Good Luck