Plumerias are small tropical trees. A healthy plumeria tree, sometimes called a frangipani or the "lei flower," will produce a multitude of very fragrant blossoms from spring through fall in tropical regions. In cooler climates, plumarias can survive if brought indoors in the winter. This tree is valued for its flowers and low susceptibility to insects and diseases. However, several fungal diseases can strike a plumeria tree, so it's good to know the signs and the remedies.
Charles Plumier was a Franciscan monk and noted botanist who lived from 1648 until 1704. During his many travels to tropical parts of the world, he identified the plumeria, which another botanist named after him.
Black Tip Fungus
You'll know if the black tip fungus has attacked your plumeria tree if you see black tips on the branches' growing tips in spring. Affected branches will stop growing. If you catch this fungal disease soon after it first appears, you'll have success in halting its spread. Spray the tree with an approved fungicide as soon as possible, and also cut affected branches back to disease-free wood.
Plumeria rust is caused by Coleosporium dominguense and Coleosporium plumeriae. The plumeria cultivars most susceptible to this fungus are the Plumeria rubra types and the Plumeria obtusa. This fungus manifests itself as red-orange pustules on the backsides of leaves. Your first line of attack should be to cut off affected leaves. Do not add them to a compost pile because the disease can spread. The Plumeria Society of America recommends using a broad spectrum fungicide---those products containing bayleton, benomyl or oxycarboxin are appropriate. Cutting down tall weeds around plumeria trees helps to improve air circulation and will reduce the humidity this pathogen needs to survive. Also, when you plant plumeria trees, be sure to leave plenty of space between trees.
Powdery mildew is a common fungal disease that affects many types of plants, from squash to plumerias. It forms a white or grey mold on the plants' leaves. To help control powdery mildew, prune off branches that are touching other branches, to improve air circulation. Also, do not plant plumeria trees too close to each other. A broad spectrum fungicide will be effective in knocking out powdery mildew.
Black Sooty Mold
Black sooty mold forms a black mold on plumeria leaves. You can help control it by controlling ants, which bring aphids and scale to your tree and feed on their sticky excretion. If you smear a think (1/2 inch) layer of a product called Tree Tanglefoot around the base of your plumeria tree, ants will be unable to pass over it. Black sooty mold can also result from exposure to whiteflies and thrips: control these pests with yellow sticky traps and insecticidal soap spray. If necessary, spray your tree with a broad spectrum fungicide.