Mitosporic or anamorphic (asexual or imperfect) fungi (Deuteromycotina) that not only lack fruit bodies but also fail to produce conidia, the thallus consisting of septate hyphae. Somatic structures of propagation or survival, termed propagules, are varied and include chlamydospores and bulbils. Hyphae are modified to form sclerotia, pseudosclerotia, rhizomorphs, strands, and cords. About 40 genera (with +30 synonyms) containing 220 species are recognized. The Agonomycetes constitute an artificial group that does not consist of closely related genera and is recognized for its practicality rather than homogeneous taxonomic composition. They are circumscribed not only by what they lack, such as conidia, asci and ascospores, basidia and basidiospores, and zygospores, but also by the apparent superficial similarity between some of the members in, for example, hyphal, chlamydospore, and sclerotial form.
Agonomycetes are generally considered to be combative species which are persistent and long-lived, largely because of the resistant nature of their vegetative structures and their slow and intermittent reproduction or complete absence of reproduction. Whether they are capable of defending captive resources and have good enzymatic competence, which are other features of combative species, is largely unknown. However, they occupy diverse ecological niches, including aquatic habitats, soil, wood in various stages of decay, other decaying plant material, and dung. They also function as root and foliar pathogens, and many cause serious diseases in terms of host damage and economic loss, especially of roots, corms, and bulbs. Agonomycetes sometimes cause damage in commercial mushroom-growing environments, and Papulaspora byssina in particular is associated with the brown plaster mold problem in mushroom beds. Armillaria, a basidiomycete with a Rhizomorpha agonomycete state, is a severe parasite of a wide range of woody and herbaceous plants. See Deuteromycotina, Plant pathology