Sunday, 15 April 2012

Frangipani blues - frangipani rust disease

If you were to search on houses for sale in Sydney, you would see that the city is littered with frangipani trees. They are everywhere, especially in the older inner-city suburbs:


Some more:














Yet increasingly these trees are being attacked by an orange invader - Frangipani Rust. The rust lives on the underside of the leaves and spreads along the leaf by rupturing. As it does, it goes from leaf to leaf, causing the leaves to discolor and drop from the tree early:


The trees end up looking bare except for their flowers (which are unaffected by the rust). The appearance of a rust-affected frangipani in full bloom is not unlike a frangipani in the dry season in a truly tropical climate - that of few leaves and many blooms, The picture below shows a rust-affected frangipani in the background in Randwick (with few leaves left) while the one in the foreground (a pink cultivar) appears less affected:


It is believed that the rust has been in Australia for around 10 years already, probably introduced from a cutting brought in from Florida (where the disease was first observed). The disease does not kill the plant, but does cause significant defoliation. This weakens the plant as specimens that are continually leafless cannot properly photosynthesize and convert sunlight into energy (which is needed for growth and flower production).

Not all frangipanis are affected equally. The common yellow and white ('Celadine') variety seems to get it worst. The pink and red cultivars don't seem to suffer as badly, while Plumeria obtusa ('Singapore White') doesn't react at all to the rust (mine does have rust on its leaves, but they do not discolor or drop prematurely).

There are sprays on the market to combat the rust, and it may be worth pursuing. The rust thrives in hot, humid conditions and is thus worst in late summer and early autumn. In places like Cairns the rust ensures that frangipanis remain leafless pretty much all year round, while the dry air in Western Australia has helped keep it at bay so far. To control it, it is important to clean away any fallen leaves that are rust affected to keep it from spreading - not much help if your neighbors don't clean theirs though!

3 comments:

  1. I wonder how prevalent it is up here in the north. I haven't spotted any on my three Plumerias yet.

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  2. The rust is really bad in Cairns (where I used to live). You only see it in wet, humid climates, so Townsville might be too dry for it to spread. WA is also rust free.

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  3. This page is very informative and fun to read. I appreciated what you have done here. I enjoyed every little bit part of it. I am always searching for informative information like this. Thanks for sharing with us.frangipani cuttings

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