Rot can start in the roots, the tips, a wound or in the heartwood anywhere. If rot is near a branch tip, the branch will have no or very small leaves, even in summer. If rot is in the roots, branches will still get energy from the healthy wood for a while but the whole plant will slowly get weaker and weaker. Rot often triggers the reproductive system to produce flowers which will use up the remaining energy even faster.
To check for root rot, poke the trunk lightly just above soil level with a thin sharp tool. If white sap comes out quickly, the trunk and, in almost all cases, the roots are healthy.
To check for rot elsewhere, look for the branch with the smallest leaves. Squeeze the branch. If it’s very soft and has black liquid inside, that part is already dead. If it’s a little soft, it’s unhealthy. It’s neither healthy or dead, it’s struggling. You can poke the branch lightly with a thin sharp tool to see how fast the sap appears.
If you poke frangipani wood and no sap appears, poke deeper, poke higher and poke lower to get an idea where life is and where rot is. Any branches that have rotted and are dead should be cut off. Try to make the last cut in healthy wood and try to make it vertical or on angle.
If you find root rot early and the branches are firm and healthy, cut all the leaves and flowers off and cut the branches off and grow them as cuttings.