Photo 2. Underside of leaf showing pustules of frangipani rust, Coleosporium plumeriae, liberating masses of spores (urediniospores).
Photo 3. Close-up of frangipani rust, Coleosporium plumeriae, pustules liberating spores (urediniospores).
Photo 4. Underside of leaf showing pustules of frangipani rust, Coleosporium plumeriae, liberating masses of spores (urediniospores).
Widespread. In the tropics and sub-tropics. Asia, North America, Oceania. It is recorded from American Samoa, Australia, Cook Islands, Federated States of Micronesia, Fiji, French Polynesia, Guam, Marshall Islands, New Caledonia, Samoa, Solomon Islands, Tokelau, Vanuatu, and Wallis and Futuna
Frangipani (Plumeria species). It also occurs on the pink or Madagascan periwinkle, Catharanthus roseus.
A serious disease causing unsightly spotting and defoliation (Photo 1). Small numerous yellow-orange spots (called uredinial pustules) occur on the underside of leaves which burst to liberate masses of spores (Photos 1-3). A tell-tale sign is to rub a finger across the leaf. If the rust is present, the powdery spores will turn the finger reddish-brown, the colour of rust - hence the name of the disease. The top of the leaf develops greenish marks (Photo 4) and, later, brown patches. and fruits are infected.
The spores are spread in the wind, but need humid conditions and leaf surface wetness to germinate and infect.
Infected leaves fall earlier than those that are healthy, and this may set back the growth of young plants, although larger trees appear to grow normally. The disease is unsightly, but will not kill the tree. In severe cases, especially under shady humid conditions, defoliation occurs.
Look for the yellowish-orange spots on the underside of the leaves. Rub a finger across the leaf (see under Symptoms & Life Cycle) to see if the spores turn the finger a rust colour.
Some varieties are more tolerant to infection than others. Get advice from nurseries, or look at the different varieties near you. The variety with white flowers appears more susceptible.
It is not economic to spray large plants in gardens with fungicides, but fungicides may be necessary in nurseries to prevent defoliation and also spread of the rust on plants for sale. If fungicides are needed use:
AUTHOR Grahame Jackson & Eric McKenzie
Photo 4. (taken by Eric McKenzie), and used in this fact sheet, appeared previously in McKenzie E (2013)
coleosporium plumeriae PaDIL - (http://www.padil.gov.au).
Produced with support from the Australian Centre for International Agricultural Research under project PC/2010/090: Strengthening integrated crop management research in the Pacific Islands in support of sustainable intensification of high-value crop production, implemented by the University of Queensland and the Secretariat of the Pacific Community.
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