Mode of Rice Blast Control by Chlobenthiazone

Mechanism of Rice Blast Control of Chlobenthiazone (Part I)

Abstract

Chlobenthiazone (S-1901), 4-chloro-3-methyl-2(3H)-benzothiazolone, is a new fungicide for the control of rice blast. Greenhouse studies indicated that the fungicide had high preventive and residual activities at low concentrations against the disease. On the contrary, curative activity was not obtained even at a concentration as high as 500μg/ml. The fungicide was also effective in controlling the disease by submerged application, indicating systemic movements in plants. When ¹⁴C-labeled chlobenthiazone was applied to the leaves or roots of rice seedlings, radioactivity was found to be rapidly translocated to the untreated parts of the plants, confirming the result in pot trials. Furthermore, the rice seedlings exposed to the fungitoxic vapor were protected from the disease. It is suggested that both the systemic and the vapor phase activities must contribute to the effective disease control in fields. Some of the field trials demonstrated that chlobenthiazone controlled rice blast by foliar or submerged application.