Rust fungi are characterised by their orange-brown dusty pustules which are often surrounded by a yellow ring, depending on the particular Rust.
They can range in severity from infections that can wipe out a crop to purely aesthetic damage. There are over 4500 different species of rust fungi of which 200 are native to the UK.
The life cycles of Rust are one of the most complicated. The life cycle can involve several kinds of spore, each of which may specialise on different plant species.
Rust fungi typically target the plant foliage, although some are known to affect fruits, flowers, petioles, tender shoots and stems.
Some species of Rust can give rise to systemic infections that may result in other plant problems, such as abnormal growth, witch's broom, stem canker, galls, or hypertrophy in some plant parts.