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Disease Control and Pest Management

Colonization of Chestnut Blight Cankers by Ceratocystis microspora and C. eucastaneae. J. S. Russin, Postdoctoral fellow, Department of Plant Pathology, University of Kentucky, Lexington 40546-0091; L. Shain, associate professor, Department of Plant Pathology, University of Kentucky, Lexington 40546-0091. Phytopathology 74:1257-1261. Accepted for publication 24 May 1984. Copyright 1984 The American Phytopathological Society. DOI: 10.1094/Phyto-74-1257.

Ceratocystis microspora and C. eucastaneae commonly colonize chestnut blight cankers in eastern Kentucky. Both of these species failed to become established in living or dead tissue from any of the 25 hardwood species, including American chestnut, into which they were inoculated. C. microspora and C. eucastaneae also failed to become established in chestnut when coinoculated with virulent (V) and cytoplasmically hypovirulent (CH) isolates of Endothia parasitica. These species, however, naturally colonized 13-mo-old cankers induced by several V and CH isolates. Ceratocystis species may serve as surrogate fungal attractants for enhancing insect dissemination of CH isolates of E. parasitica. Growth and sporulation of Ceratocystis was reduced on a healthy bark extract (HBE) medium compared to those on a blighted bark extract (BBE) medium. In addition, growth of Ceratocystis was increased on Noble agar that previously supported mycelium of V or CH isolates of E. parasitica. Healthy bark extract contained antifungal compounds not detectable in BBE and contained much higher levels of condensed and hydrolyzable tannins than BBE. Establishment of Ceratocystis in blight cankers apparently is enhanced by the action of E. parasitica to modify inhibitory compounds in healthy bark, and to produce metabolites that directly stimulate Ceratocystis. The evidence suggested that C. microspora becomes established in chestnut blight cankers prior to C. eucastaneae.