Susceptibility of Melaleuca quinquenervia to Botryosphaeria ribis, a Potential Biological Control Agent. M. B. Rayachhetry, Former Graduate Research Assistant, Department of Plant Pathology, University of Florida, Gainesville 32611. G. M. Blakeslee, Associate Professor, School of Forest Resources and Conservation, and R. Charudattan, Professor, Department of Plant Pathology, University of Florida, Gainesville 32611. Plant Dis. 80:145-150. Accepted for publication 9 November 1995. Copyright 1996 The American Phytopathological Society. DOI: 10.1094/PD-80-0145.

Isolates of Botryosphaeria ribis from Melaleuca quinquenervia and Rhizophora mangle were evaluated for pathogenicity to M. quinquenervia clones under greenhouse conditions. Stem inoculations revealed (i) B. ribis induced cankers on stems that were similar to those observed in natural infections under field conditions, (ii) the mid-height segment of the main stem was more readily colonized than the root collar, (iii) a slightly positive correlation occurred between diameter of stems at the point of inoculations and canker lengths, (iv) hyphae and macroconidia were similarly effective as inocula for stem cankers, (v) more pronounced callusing occurred following inoculations during March than during October, (vi) all isolates initiated cankers on stems of all clones but some isolates exhibited greater aggressiveness, (vii) M. quinquenervia clones showed a differential susceptibility to infection by B. ribis, and (viii) establishment of this fungus in stem tissues requires a wound or some form of injury that stresses the tree