Rust color all around in south florida?

I notice that certain parts tered all around south fl from palm beach county to dade county have rust stains all over the vegetation (gr, palm trees base), side walks, street curbs, light poles, fenses and even the base of some houses and building structures. Im just curious what causes this and how anybody would even get rid of this issue in these areas, I see it all the time down in south fl but barely see it in central and north florida.