Conidia (tretispores) are produced in
branching chains. Characteristically the conidia have an extended apical
prolongation. This is relatively short in saprophytic species like A.
alternata but commonly forms a long 'beak' in parasitic species. This common
saprophyte grows in abundance on senescent and dead graminaceous leaves and is one of the
species that turns maize leaves almost black in late fall.