ABSTRACT
Phytophthora diseases occur commonly in Japan, including pineapple heart rot (A–B) in Okinawa, Phytophthora diseases of orchid (E) in Chiba, and Zanthoxylum piperitum (C–D) in Nara. Pineapple heart rot (A–B) disease started rotting internally, and the basal rotted leaves were readily removable. The disease was caused by both Phytophthora nicotianae var. parasitica and Phytophthora cinnamomi. Phytophthora disease of orchid (E) disease was caused by Phytophthora nicotianae var. parasitica. The blighted lesions occur abundantly on leaves. Phytophthora disease of Zanthoxylum piperitum(C–D) diseased plants were discolored and weakened. The root systems were poor and also darkened. The disease was caused by an unidentified Phytophthora species. In pathogenicity tests, the three-month-old rooted cuttings inoculated by burying the inoculum of P. megasperma in the soil near the healthy cuttings grown in pots or dipping the roots in the inoculum suspension were seriously damaged, especially when artificially wounded prior to inoculation by cutting a part of the roots.
