Abstract
The disease symptom first appeared on leaves as yellowish discoloration and was characterized by following production of grayish white lesions in various sizes on leaves of tulip plants. The symptoms are similar to those of tulip blossom blight caused by Phytophthora cactorum although the stems are not softly rotted. Cultivars ‘Red Matador’, ‘Ben van Zanten’, ‘Parade’, and ‘Queen of Night’ were susceptible and these varietical spectrum differed from those to tulip blossom blight. The pathogens were identified as Pythium dissotocum, P. afertile, P. sylvaticum and other unidentified one belonged to Pythium ‘group P’. Although retardation of growth of bulbs appeared, bulbs and roots were not infected. The weeds such as Polygonum conspicuum, Digitaria adscendens and Cyperus serotinus may be a major carrier of the disease.
