Infection is usually local, i.e. forming individual colonies in leaves or other aerial parts of the host and dependent on re-infection each year, but infection is sometimes systemic and persistent in the plant. Life cycles are usually complex, involving up to five distinct types of spore and often two different hosts. IV basidium basidiospore Basidia develop from teliospores and so have no independent existence as a spore stage on the host.
Rusts commonly omit one or more spore stages in their life cycle.
Those with all five stages are described as macrocyclic . Note that urediniospores usually germinate to produce lesions that produce more uredinia. This allows rapid asexual spread during a single growing season and also enables a heteroecious species to persist on one host, even when its other host is not present. This means, in this case, that wild grasses do not act as a reservoir of infection even though they may carry the rust. In heteroecious rusts, it is often the case that two or more formae speciales occur on a single host but differ in their alternate host species.