I have an orange powdered substance on the underside of my Frangipani leaves. What is it and how do I treat it

The orange-powdered substance that you have on the undersides of your Frangipani leaves is rust. It will be best to rake up all the affected fallen leaves and dispose of them.

To control rust, we recommend 'Yates Rose Shield - Black Spot & Insect Pest Killer'. All-in-one product for the control of various insects, diseases and mites, for use on roses and ornamental plants.