Pathogenicity of Ganoderma Species in California Agricultural and Native Hosts

Ganoderma species have been associated with wood decay of dead or dying trees in agricultural and native forests in California. Pathogenicity tests were used to determine the pathogenicity of Ganoderma adspersum and G. brownii on young, healthy trees of peach rootstock 'Nemaguard' (Prunus persica × P. davidiana), peach-almond hybrid rootstock 'Viking' [P. persica × (P. dulcis × (P. cerasifera × P. armeniaca))], walnut rootstock 'VX211' (Juglans microcarpa × J. regia), pistachio rootstock 'UCB1' (Pistacia vera), blue oak (Quercus douglasii), and valley oak (Q. lobata). Inoculations were made by coring into the sapwood at the root collars and pipetting Ganoderma spore solutions into the wounds. In two greenhouse trials, 10 months postinoculation, trees had no visual, external symptoms of disease, though there were differences in the extent of internal wood decay and xylem discoloration. G. adspersum caused extensive wood decay and discoloration and was reisolated from 'Nemaguard' and 'Viking'. The data suggest that this species was capable of infecting healthy sapwood and may be a pathogen of young trees.