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An In Vitro Test for Evaluating Efficacy of Mycoparasites on Sclerotia of Sclerotinia sclerotiorum. J. D. Mueller, Graduate Research Assistant, University of Illinois, Urbana-Champaign 61801. Molly Niedbalski Cline, Postdoctoral Extension Associate, J. B. Sinclair, Professor of Plant Pathology, and B. J. Jacobsen, Professor of Plant Pathology, University of Illinois, Urbana-Champaign 61801. Plant Dis. 69:584-587. Accepted for publication 9 December 1984. Copyright 1985 The American Phytopathological Society. DOI: 10.1094/PD-69-584.

A modification of Kohnís technique for apothecial induction in the Sclerotiniaceae was developed to test the efficacy of mycoparasites on sclerotia of Sclerotinia sclerotiorum. The modification is an incubation period at 25 C prior to Kohnís initial cold treatment. The new method was compared with the previously used method of pairing the fungi on an agar medium (such as potato-dextrose agar) and determining the effects on growth of S. sclerotiorum mycelium. This method tested the effects of Gliocladium roseum, G. virens, Trichoderma harzianum, and T. viride on carpogenic germination of S. sclerotiorum. Numbers of carpogenically germinating sclerotia and apothecia produced per sclerotium were used to measure the effects of the mycoparasites. Mycoparasites were also evaluated on the basis of their percentage of reisolation from sclerotia. A good separation of the fungi was obtained using this technique. G. virens was the mycoparasite most frequently recovered from S. sclerotiorum sclerotia and significantly reduced all measurements of carpogenic germination.