i have white cottony stuff growing on the leaves of my frangipani tree, and it is causing sticky stuff to form and rapidly dropping. It is even on the baby leaves that are just coming out. Also frangipani is not listed on your app.
Without pictures, I am going to have to make an assumption concerning the problem. I suspect you have mealybugs. They are known to appear as white, cottony masses and are very sticky. They do cause growth distortions and will result in decline of the tree.
The simplest way to deal with them is to remove, or wash, them from the tree with a hard stream of water. There are other measures, such as mixtures of vegetable oil and liquid laundry detergent, that can be sprayed to remove them. If you prefer something a little more toxic, but still safe for the environment, pets, etc., then neem oil or other insecticide oil/soaps are available. There are harsher chemicals if you feel these "softer" methods are not working.