Rust Disease
Rust disease is a classification of diseases caused by pathogenic fungi of the order Pucciniales.
Rust fungi are highly specialized pathogens with several unique features. Taken as a group, rust fungi are diverse and affect many kinds of organisms. However, each species has a very narrow range of hosts and cannot be transmitted to non-host plants. In addition, most rust fungi cannot be grown easily in pure culture.
A single species of rust fungi may be able to infect two different hosts in different stages of its life cycle, and may produce up to five morphologically and cytologically distinct spore-producing structures in successive stages of reproduction. Each spore type is very host specific, and can typically infect only one kind of organism.
Rust fungi are obligate pathogens that only infect living creatures. Infections begin when a spore lands on the organism's surface, germinates, and invades its host.
The only known cure for most types of Rust Disease is the Rust-Eater mushroom, which is a rare plant that only the Fertile Kingdom possesses. No one knows for sure where they get it from, or how it's made. The only information about this mushroom is that it will die unless it can eat the type of rust fungi that it was designed to eat. Afterwards, the Rust-Eater dies.