ABSTRACT
Phellodendron amurense is one component of the natural flora in the twenty-hectare garden of The Institute for Nature Study, Natural Museum in Tokyo, Japan. Among a total of 155 mature trees (9-76 cm in diameter at breast height) in the garden, 36 trees were dead and nearly 30 trees were diseased by the end of December 1993. Diseased trees were characterized by loss of turgidity and delayed new leaflet development in the spring. Leaflets that developed on the diseased trees were smaller than those on healthy ones. Canopies of the diseased trees were less dense than those of healthy trees because of less numerous and smaller leaflets. As disease progressed, new leaflets did not develop in the spring, and dieback of twigs occurred, resulting in the decline of the entire trees. Diseased trees had damaged root systems. The number of the lateral roots was reduced, and there increased the numerous discolored roots.
