While some species of frangipani appear to be resistant to frangipani rust, it’s our theory that frangipani rust is constantly evolving and continuously producing new strains of frangipani rust. Observing one species of frangipani in one location is not a completely accurate way to determine the vulnerable and resistant of a frangipani species.
In our experience, about twelve or thirteen years ago, the common rubra species was the only species affected by the frangipani rust fungus. All the other frangipani species appeared to be resistant. At the time, obtusa frangipanis were becoming very popular because they appeared to be resistant to the fungus. Three years later, unfortunately, some of our obtusa species started to get rust and wherever it was left untreated, nearby obtusa frangipanis got infected as well.
The following year, we found one frangipani obtusa tree with rust which was amongst many uninfected rubra frangipanis. This indicated to us that frangipani rubras were resistant to the frangipani obtusa rust.
A couple of years later, we noticed some pink pudica frangipanis badly infected and worse than all the surrounding species. Although it would have been better to notice and treat these frangipanis earlier, we were able to eliminate the rust in that area quickly effectively.
About five or six years ago, we received a load of white pudicas from northern Australia which had until that time appeared to be completely resistant to frangipani rust. To our surprise, a few leaves on one plant had rust. We checked all the plants, cut off and meticulously burnt the infected leaves and we have not seen rust on our frangipani pudicas since. Another effective strategy for us to fight rust has been to keep large quantities of pudica and propagate our own cuttings.
It’s our belief that when frangipani rust travels from one plant to another, that rust is very unlikely to infect different species of frangipanis. However, when rust is left untreated and allowed to increase, the rust is more likely to have a greater chance to evolve and adapt and survive on similar but different species of plant.
If you think frangipani rust is an important factor in choosing a frangipani species, our advice is to focus more on the foliage, flowers, hardiness etcetera and if it gets rust, treat it as early and as often as possible until it disappears.