Field observations and inoculation experiments to determine the nature of the carpophoroids associated with Entoloma abortivum and Armillaria

Carpophoroids traditionally attributed to Entoloma abortivum (“Aborted Entolomas”) represent malformed Armillaria fruiting bodies permeated by E. abortivum hyphae, as shown by our field observations and preliminary laboratory work. This contradicts the generally accepted hypothesis that carpophoroids are E. abortivum fruiting bodies colonized by Armillaria. Carpophoroids possess many of the structural characteristics of Armillaria fruiting bodies, including growth and development from rhizomorphs and the production of Armillaria-like spores on basidia. Our inoculation experiments demonstrate the ability of E. abortivum to abort the development of A. tabescens fruiting structures in vitro. In rare instances the introduction of E. abortivum disrupts A. tabescens fruiting structures to the point where they macroscopically resemble immature carpophoroids as observed in nature. If E. abortivum is a parasite of Armillaria species under natural conditions, E. abortivum may contribute to the regulation of Armillaria populations and could be investigated as a candidate for the biological control of destructive Armillaria species. We recommend “Abortive Entoloma” be used as the common name for E. abortivum.