Abstract
A joint study on ear blighting of rice plant was conducted by seven Agricultural Experiment Stations located in seven Prefectures of Tokai-Kinki Region from 1969 to 1971. The obtained results are reported in this volume by the investigator (s) of every Prefecture. The results of the joint study are summarized as follows:
1. Helminthosporium oryzae (=Cochliobolus miyabeanus) was found to be the most prevalent causal fungus of rice ear blighting in Tokai-Kinki Region. Cercospora oryzae (= Sphaerulina oryzina) and Fusarium nivale were also found to be the major pathogen in some locations or in a certain year. Mixed infection with two or more of those pathogenic fungi including Pyricularia oryzae was often observed. Helminthosporium sigmoideum var. irregulare attacked the uppermost internode only in special occasion. Alternaria sp., Cladosporium sp., Curvularia sp., Epicoccum sp., Fusarium sp., Nigrospora sp. and Phoma sp. were also seen on the samples of ear blighting, but they are not considered to be the essential cause of the disease because of the lack of distinct pathogenicity.
2. There was high correlation in some cases, while low or no correlation in other cases between the grade of leaf blade infection and panicle infection with Helminthosporium oryzae. The results were variable especially in the farmers' fields covering large area, where the cultivation practices were different in many aspects. The pot tests indicated, however, that the rice plants liable to leaf blade infection with H. oryzae were also liable to panicle infection with the fungus. It may be said, therefore, the counterplan should be considered against ear blighting when the leaves are severely attacked by H. oryzae by the time of heading.
