MANILA, Philippines - Plumeria, Frangifani or “Kalachuchi” is one of the more popular small trees used in landscaping. The plant is a very strong grower that thrives in neglect, so much so that it is a favorite tree for landscapers to use as shade plant in public areas, cemeteries and in locations where water is wanting.
Because to decades of breeding worldwide, different flower color forms, flower sizes, leaf variegation forms and different leaf shapes are coming out in the market for the past 4 decades. It is because of this diversity that the Plumeria graduated from its “Temple and Cemetery Plant” image to a cosmopolitan landscaping material. It is now the “IN” thing to have the hybrids in homes in Thailand, Indonesia and Malaysia. Big trees of Plumerias are being dug up from cemeteries in Indonesia for landscaping jobs in the metropolitan Jakarta. The Thais have changed the name of Plumeria in the early 90’s from the lonely “Lanthom” to the happier “Lilawadee” and created marketing success locally (Thailand).
Plumerias are believed to have originated from the dry areas of Central and South Americas. When planted in the warm wet tropics, the trees get infected with Plumeria Rust or Coleosporium domingoense (syn. Coleosporium plumeriae).
Trees infected by the Plumeria Rust shed the lower leaves resulting in scanty foliage just before summer. This defeats its purpose as shade plant.
Infection sets in during wet months and gets really devastating towards the end of rainy season. Infected leaves start off with orange pustules under the leaves. The bumpy growths do not rub off easily. As the yellow-orange fungus spores are released into the air, the base tissues parasitized by the fungus become brown while the top portion of the leaves turn patchy yellow then brown. More than 90% of the leaves may be lost in one season.
The Plumeria Rust has been around since early 70’s. Although not a major disease at that time, when there are more host plants around and the pathogen reflux within a population of Plumeria, the damage may be devastating.
Disease management
According to Dr. Richard Criley of University of Hawai’i at Manoa, the Plumeria Rust is very specific in its host range. It infects only Plumerias. Plumeria rubra and its hybrids are the most susceptible. Plumeria obtusas are partially susceptible while Plumeria punica is moderately susceptible while Plumeria caracasana and Plumeria stenopetala are reportedly resistant to the fungus.
The infection spreads very fast in a Plumeria collection. Once a plant is infected, the chances of other Plumeria plants being infected will be exponentially high. By the time infected leaves are shed and the orange pustules appear on the leaves, it is too late already because of the shear number of spores floating around in the air.
Dense planting of Plumeria should be avoided and planting resistant varieties and species will be the norm of the future.
Several fungicides were tested to be effective for control of Plumeria Rust: Mycobutanil, Azoxystrobin and Triforine.
Sanitation plays a big role in management of the fungus. Fallen leaves carry lots of spores that serve as inoculum to other Plumeria plants. Fungicidal spray may not be enough if leaves will serve as the next generation of fungi. Fallen leaves should be collected in bags and burnt. Avoid carrying the leaves around where other Plumerias are planted as this will spread the spores around.
Plumeria is a dry biome plant. It is generally best to plant at the Plumerias in the western side of the country where it is drier.
The Plumeria Rust has not been observed on Adenium obesum (Bangkok Calachuchi).