First Report of Dichotomophthora indica as a Pathogen of Myrtillocactus geometrizans and Gymnocalycium mihanovichii var. friedrichii in Arizona. C. M. Pfeiffer, Acre, Inc., 4429 North Highway Drive, Tucson, AZ 85705. J. E. Wheeler, D. A. Bach, and R. L. Gilbertson. Acre, Inc., 4429 North Highway Drive, Tucson, AZ 85705; Bach’s Greenhouse, 8602 North Thornydale, Tucson 85714; and Department of Plant Pathology, University of Arizona, Tucson 85721. Plant Dis. 73:81. Accepted for publication 20 October 1988. Copyright 1989 The American Phytopathological Society. DOI: 10.1094/PD-73-0081E.
A dematiaceous hyphomycete identified as Dichotomophthora indica Rao was isolated from diseased tissue of Myrtillocactus geometrizans (Mart.)Cons. and Gymnocalycium mihanovichii (Fric & Gurke) Br. and R. var. friedrichii Werd. The diseased cacti were from a commercial greenhouse where attempts had been made to graft G. m. var. friedrichii onto M. geometrizans. The fungus colonized wounded tissue surrounding the graft area and invaded the rootstock and scion. Lesions created by the fungus on M. geometrizans were brown to black, and infected tissue was collapsed. Infection of G.m. var friedrichii by D. indica resulted in a grayish dry rot. Koch's postulates were used to verify that D. indica was the casual agent of the disease of M. geometrizans and G. m. var. friedrichii. To our knowledge, this is the first report of D. indica occuring on a host other than Portulaca oleracea L. (1).