My plumeria has yellow eggs underneath the leaves Some are heavily infested What is it What can you do to eliminate it The bush is about 8 years old and has never had this disease before?

Answer 1

Leif Forsberg, Department of Primary Industries and Fisheries Frangipanis (Plumeria rubra) are well-established garden and landscape plants in Queensland. These plants are generally easy to grow and, apart from one fungal disease called rust, are free of other major disease problems. They are rather unusual looking plants, with stubby branches and large leaves. Frangipanis are deciduous, providing useful shade and large, waxy and fragrant flowers in summer, but allowing welcome sunlight through their bare branches in winter. A disease called frangipani rust, caused by the fungus Coleosporium plumeriae, is now a firmly established and serious problem of frangipanis, detracting from their appeal. This rust fungus does not have any other known hosts other than frangipani. The disease has been confirmed to be present in Queensland since 1993. How the disease was introduced is not known. Symptoms of rust include many small, bright-yellow pustules on the undersides of leaf surfaces. These pustules rupture to release masses of powdery, yellow spores. The spores, falling from infected leaves onto stems and leaves below, make them appear as if dusted by yellow powder. Heavily infected leaves fall prematurely. Rust diseases are difficult to control once well established. Nursery professionals growing frangipanis in areas where rust occurs can prevent rust by spraying regularly, before any symptoms occur, using protectant fungicides such as chlorothalonil or copper oxychloride. Where rust pustules are present, more specific rust fungicides such as oxycarboxin can be used. Good spray coverage, and the initiation of a spray program before symptoms occur or at very early onset of disease, is important. Cuttings should come from disease-free plants. Rust infections, although not visible, may still be present in leafless cuttings. In gardens it is not advisable or desirable to spray large plants. A number of broad-spectrum mixtures that help to control rust, various other fungal diseases and pests of garden plants in general are available to home gardeners and may be used on small plants (see Table 1). Removing infected fallen leaves may reduce inoculum sources for the next season's crop of new leaves. However, air-borne spores from other frangipani sites will probably re-infect the plant.

Unfortunately, garden plants will just have to live with this problem, although nurseries should and can provide rust-free frangipanis. The rate of build-up of this disease may vary from year to year. In some years, drier conditions may slow down the rate of rust development so that plants will still remain attractive for long periods. So don't get out the axe, but rusty frangipanis are here to stay.