Disease Note.

The Occurrence of Calcarisporium parasiticum on Isolates of Botryo-sphaeria quercuum from Oak Trees in Delaware. A. L. Morehart, Department of Plant and Soil Sciences, University of Delaware, Newark 19717-1303. Plant Dis. 78:101. Accepted for publication 13 October 1993. Copyright 1994 The American Phytopathological Society. DOI: 10.1094/PD-78-0101E.

Studies to determine the etiology of crown dieback of oak trees in Delaware commercial woodlots revealed the presence of several canker-forming fungi, with Botryosphaeria quercuum (Schwein.) Sacc. predominating. The white mycelia of the mycoparasite Calcarisporium parasiticum Barnett were found growing over the darkly pigmented colonies of B. quercuum in five of 64 cultures. The five B. quercuum isolates infected naturally by the mycoparasite were obtained from adjacent red oak (Quercus rubra L.) trees at a single study site. C. parasiticum was identified by cultural and microscopic comparison with the original isolates of Barnett (I). C. parasiticum grew readily on all Delaware cultures of B. quercuum tested. This fungus, first described in cultures of Physalospora obtusa (Schwein.) Cooke obtained from diseased oak trees in West Virginia, was shown to be parasitic on a variety of plant-pathogenic fungi in culture (1). This is the first report of C. parasiticum in the mid-Atlantic region. Little is known about the ecology of this fungus or its potential to interact with plant-pathogenic fungi in nature