Phytophthora cinnamomi causes root rot of Larix kaempferi seedlings

Abstract

As part of the Forestry and Forest Products Research Institute’s grant project, “Advancement of Diagnostic Techniques and Control Methods for Seed and Seedling Diseases,” we have been investigating seedling diseases of sapling trees in Japan. During this survey, we identified a root rot affecting Japanese larch seedlings. The disease was characterized by systemic wilting and occurred from spring to summer. Isolation tests revealed the presence of Phytophthora cinnamomi in the roots and rhizosphere soil of the affected seedlings. Inoculation tests using soil-mixed inoculum successfully reproduced the root rot symptoms, indicating that this pathogen is the causal agent. We therefore propose the name “Japanese larch seedling root rot” for this disease.