What are these orange spots underside of Plumerias

http://living.thebump.com/treat-leaf-rust-disease-plumeria-5500.html

http://www.heirloomgardenexperts.com/uploads/files/plumerias.pdf?phpMy

Heirloom gardens is a PDF about plumeri.

here is answer to your question:

INSECTS & DISEASES

Plumerias are susceptible to several insect pests, most notably spider mites. If infestation should occur, treat it with Safer Insecticidal Soap or a general purpose insecticide.

In the Gulf Coast, the most common disease on plumeria is rust, characterized by bright orange “rusty” spots on the underside of leaves and yellow spotting on the top. The best way to control rust is with a preventative spray. Spray when new leaves emerge in the spring and regularly during the growing season — about every two weeks.

Should yo ur plumerias get rust nevertheless, strip off and destroy the leaves. DO NOT COMPOST THEM. Begin spraying when new leaves appear and every two weeks during the growing season.

It is probably a fungus. Check at your local garden center for treatment.

Rust