Epidemiological Studies of Rice Blast Disease Caused by Pyricularia oryzae Cavara (III)

Diurnal Pattern of Conidial Release and Dispersal Under the Natural Conditions

Abstract

Conidial release and dispersal pattern of rice blast fungus, Pyricularia oryzae, were surveyed at one hour interval in the field conditions using three different types of spore trap in July of 1987. Under clear day condition, conidial release from naturally infected lesions and dispersal pattern exhibited one distinct peak around 7 a.m. Under continuous cloudy conditions, however, the appearance of peak continued relatively longer from 1 a.m. to 9 a.m. and two to three peaks were observed. During July 14-15, a continuous cloudy condition, temperature was around 22C and relative humidity was over 93% which are considered as optimum conditions for successful penetration of P. oryzae. Conidia produced under those conditions might have more important role as effective inoculum than conidia produced under a clear day condition.