Fungicide for Rust
I recently planted a row of cannas and although I have tried my best to keep the foliage dry, some of the lower leaves have contracted a minor rust infection. After doing some homework online, I know that I have quite a few organic remedies to choose from, including baking soda, milk, sulphur, chamomile tea and neem oil. However, while some sites mention that a certain spray actually *kills* the rust fungi, others claim that it is merely a preventative, or even worse, that it doesn't work at all. Is there a definite, tried-and-proven fungicide for rust, or does it (like many things organic) depend on a lot of other individual factors?
Just to clarify things, the usual advice I see in forums is to remove all infected foliage and cut back to the ground. However, this is not a preferred alternative for me, as I live in a tropical region and hence my plants do not die back and go into dormancy during winter. Rust is also very prevalent in my climate, which is why I would prefer a fungicide over a mere preventative (so I can stop the infection in its tracks instead of constantly having to spray to prevent further spread).
Also, if all else fails, I wouldn't mind a non-organic solution if it is possible for me to apply it directly to the infected areas (e.g. with a cotton bud), without affecting the rest of the plant or hurting my garden's biological diversity. Any help appreciated, thanks.