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Disease Control and Pest Management

Biological Mode of Action of Flutolanil in Its Systemic Control of Rice Sheath Blight. Takashi Hirooka, Biological Research Center, Nihon Nohyaku Co., Ltd., 4-31 Honda-cho, Kawachi-nagano, Osaka 586, Japan; Yukio Miyagi(2), Fujio Araki(3), and Hitoshi Kunoh(4). (2)(3)Biological Research Center, Nihon Nohyaku Co., Ltd., 4-31 Honda-cho, Kawachi-nagano, Osaka 586, Japan; (4)Laboratory of Plant Pathology, Faculty of Bioresources, Mie University, Kamihama-cho, Tsu 514, Japan. Phytopathology 79:1091-1094. Accepted for publication 19 May 1989. Copyright 1989 The American Phytopathological Society. DOI: 10.1094/Phyto-79-1091.

The systemic fungicide flutolanil is used to control rice sheath blight caused by Rhizoctonia solani with application of granules to the paddy in Japan. We studied the effect of flutolanil on the infection process of R. solani by this application method. In a greenhouse study, a linear correlation (P<0.001; r=0.944) was obtained between the log of flutolanil concentration in rice leaf sheaths and disease suppression, with approximately 1.8 g/g of flutolanil in leaf sheaths contributing to about 80% suppression. Percent inhibition of hyphal growth and infection-cushion formation of R. solani on leaf sheaths increased as the amount of active ingredient increased, with 2 g/g of flutolanil in the leaf sheaths causing about 80% inhibition. Micromanipulation in a scanning electron microscope revealed that penetration from infection cushions was completely inhibited on leaf sheaths containing approximately 2 g/g of flutolanil. These results suggest that the inhibitory effects of flutoalanil on fungal growth and penetration depend on flutolanil concentration in leaf sheaths.