The following are the similarities between rust and smut:Rust and smut are fungal diseases that affect plants, and are called obligate plant pathogens.The mycelium that causes these both diseases pass through two stages; (i) the monokaryotic (primary) stage and (ii) dikaryotic (secondary) stage.The teleutospores in both diseases are resting spores and on germination, produce basidiospores. Ustilago tritici is the only exception.