Heteroecious

Heteroecious is an adjective used in parasitology and plant pathology to describe a parasite or pathogen whose life cycle requires two or more distinct host species to complete development and reproduction. The term comes from Greek elements meaning “other house.”

In practice, heteroecious organisms often alternate between different hosts, performing different stages of their life cycle on each host. In rust fungi, for example, heteroecious species may produce sexual spores on one host and asexual spores on another, with substantial portions of their development tied to the biology of each host species. This reliance on multiple hosts makes their life cycles more complex and, in some cases, more difficult to manage.

Well-known examples include rust fungi with alternating hosts. Puccinia graminis f. sp. tritici, the stem rust of wheat, requires barberry (Berberis) as an alternate host for sexual stages, while producing urediniospores on wheat. Cedar-apple rust, caused by Gymnosporangium juniperivirginianae, alternates between juniper (Juniperus) and apples (Malus). White pine blister rust (Cronartium ribicola) uses a pine (Pinus) as one host and currants or gooseberries (Ribes) as the other. Many heteroecious rusts have historically driven management practices that aim to remove or manage the alternate host to disrupt the life cycle and reduce disease pressure.

Heteroecious life cycles are contrasted with autoecious life cycles, in which the pathogen can complete all stages on a single host species. Understanding whether a pathogen is heteroecious informs disease forecasting and control strategies in agriculture and forestry.