Root and Root Collar Disease of Eucalyptus grandis Caused by Pythium splendens . C. LINDE, Department of Microbiology and Biochemistry, University of the Orange Free State, P.O. Box 339, Bloemfontein, 9300, South Africa. M. J. WINGFIELD, and G. H. J. KEMP, Department of Microbiology and Biochemistry, University of the Orange Free State, P.O. Box 339, Bloemfontein, 9300, South Africa. Plant Dis. 78:1006-1009. Accepted for publication 2 May 1994. Copyright 1994 The American Phytopathological Society. DOI: 10.1094/PD-78-1006.

A serious root and root collar disease of Eucalyptus grandis occurred in the Kwambonambi area of northern Natal during the past 4 yr. This disease typically occurs on young trees that rapidly wilt and die. Pythium splendens was consistently isolated from roots and root collars of dying trees. P. splendens inoculated on two different clones of E. grandis and on Eucalyptus fastigata was highly pathogenic. Isolates of P. splendens showed the same or an even higher degree of virulence than Phytophthora cinnamomi, a well-known Eucalyptus root pathogen, on the E. grandis clones tested. Virulence of P. splendens on E. fastigata was, however, less than that of Phytophthora cinnamomi.