每日吃瓜

My bonsai has developed white fungus & is now losing it's leaves.
How do I nurse it back to good health please? See attached picture, thanks.

You have a fukien tea tree (carmona). There are nobody that know how to keep them healthy here but thousends of questions like yours. All I can say is for next tree, read up on the species before purshase. Get locally hardy trees and grow them outdoors.

The fungus lokos suspiciously like mealy bugs to me. Check. If so, remove & treat the plant.