Mycoparasitism of sclerotial fungi by Teratosperma oligocladum

Sclerotia of Sclerotinia minor were parasitized by Teratosperma oligocladum, a recently described dematiaceous hyphomycete. The mycoparasite was cultured on living sclerotia placed on water agar and on sclerotia in moist sand. It grew poorly on several common laboratory media but growth in vitro was enhanced by supplements of soil extract and, especially, by aqueous extracts of sclerotia. Sclerotia of S. minor, S. sclerotiorum, S. trifoliorum, Sclerotium cepivorum, and Botrytis cinerea were parasitized in vitro, but sclerotia of Sclerotium rolfsii and Macrophomina phaseolina were not. Macroconidia of T. oligocladum germinated on membrane filters placed on soil containing sclerotia of S. minor but not on soil without sclerotia. Sclerotia of three Sclerotinia spp. were infected within 2 weeks in soil infested with the mycoparasite. Teratosperma oligocladum parasitized and destroyed all of the sclerotia of S. minor buried in a natural soil by 10 weeks. Parasitism was equally good at 20 and 25 °C, but occurred more slowly at 15 °C. No parasitic activity occurred at 30 °C. The morphology, cultural characteristics, and mycoparasitic habit of T. oligocladum indicated that it was similar in many respects to the mycoparasite, Sporidesmium sclerotivorum, and that it is a potentially useful agent for the biological control of sclerotial plant pathogens.