Abstract
This report deals with morphological, physiological and pathological characteristics of Phytophthora sp. causing a new disease of tulip in Japan. The disease occurs most conspicuously in the field from late-April to mid-May after rain. On the young plants, the symptoms appeared at the basal part of the plants to whole plants within four or five days. In adult plants, the first leaf axil and stem were usually infected. The diseased stems changed to yellowish-white in color and shrunken. The infected bulbs showing the symptom of dry rot with black color could hardly be observed. The causal fungus was isolated and identified as Phytophthora cactorum Schröter, the pathogen of tulip blossom blight. The fungus was transmitted to the tulips via soil, but not by bulbs even if they were obtained from heavily infected plants. The fungus is pathogenic to the other bulbous plants such as Allium and Hyacinthus but not to Lilium.
