Lately my inbox has been flooded with cases of Frangipani rust. The ‘rust’ is a fungus, which attacks the leaves and stems of frangipani trees. The rust is very unattractive and causes premature leaf drop. Frangipani trees that are severely affected year after year can be weakened, but the disease is rarely fatal. The frangipani rust is on the increase as we head into the wet season, and the more humid weather provides the perfect conditions for this fungus to grow. When rust takes hold leaves, will yellow, wilt, and fall off. Your frangipani could be left completely leafless.
Rainfall and high humidity increase the incidence of the disease. Protective copper based sprays can be applied as preventative measure, but are largely ineffective once rust symptoms have already become evident. Fallen leaves can be a source of infected material. Collecting and removing these is one strategy to reduce infection. Any neighboring trees that are infected will provide a wind borne source of fungal spores, so it can be rather hard to control rust, as neighbors may have an outbreak at a different time of the year. Frangipani are literally everywhere in Bali, so it is easy for this fungus to spread like the plague.
The rust is most noticeable as we move into the wet season. Small yellow ‘pustules’, or sacs appear on the underside of the leaves. They open and release spores, which then re-settle on other frangipani trees, spreading the disease. Severe rust infections, particularly in young plants, may cause the leaves to drop prematurely and even lead to the death of the plant.
What does frangipani rust look like?
Several bright gold or white dots known as “pustules” appear on the underside of a frangipani leaf. The number of pustules increases until covering most of the underside of the leaf. The pustules contain a powdery substance, which spores through the air and infects nearby frangipani leaves. Badly affected leaves shrivel up, turn brown and die. The surrounding ground below the tree may be covered with rust infected dead leaves.
Rust-free leaves will appear at the end of the wet season heading towards April and May. The rust problem will disappear at this time but is likely, unless treated, to appear again around November-December, or even earlier.
Frangipani rust can easily jump, or blow, from one frangipani tree to another. It is important to dispose of all rust affected leaves. Prune rust affected leaves from the tree, and dispose of any that have fallen to the ground. Do not add rust affected leaves, or any diseased vegetation for that matter, to the compost. These diseased leaves must be thrown out in the rubbish.
Spraying against frangipani rust
In the case of frangipani rust the most effective control is to spray with a fungicide. Whether you use an organic or chemical fungicide the problem may still be difficult to control. Fungicides such as Mancozeb and sulfur, which are available for home garden use to control rust and other fungal problems, are most effective.
You could try using a general fungicide to slow the development of the disease such as Yates Spray Insecticide and Pesticide, which contains sulfur and Mancozeb. If you prefer organic solutions you can try a mixture of powdered milk, water and dish soap. Some gardeners swear by using chamomile tea if the infestation is severe. Mancozeb will most likely have a much quicker results than any organic remedy for this problem. You need to do is to maintain a film of fungicide on the underside of the leaves, to prevent the rust from taking hold. It is important to spray every two weeks between October and February to prevent rust from forming on the frangipani leaves. It is important to spray every leaf, especially on the underside. The problem will reappear in humid periods of the year. Rusts are generally very difficult to control.
You don’t have to spray, if you don’t want to. The frangipani rust, unsightly as it is, rarely kills frangipani. Just make sure that all diseased leaves are either pruned or cleaned from the ground and disposed of properly to prevent re-infection of the tree
Rust is a sign that the trees are lacking trace elements. Add seaweed fertilizer, seasol, or fish emulsion, twice a year to the soil. Keeping your plants well nourished will help prevent future fungal infections. Potash is also particularly good for improving disease resistance in frangipanis. Frangipani rust can be a very tough problem, so hang in there!
Now is a good time to get on top of any gardening problems that you may have, so don’t hesitate to contact me with your questions.
Merry Christmas and a Happy New Year to all!
