Tiadinil is a novel systemic fungicide for rice diseases discovered and developed by Nihon Nohyaku Co., Ltd. The compound is characterized by a unique heterocyclic moiety, 1,2,3-thiadiazole, and a unique mode of action of inducing the plant defense mechanism against a pathogen. The lead compound was found in the synthesis research of 1,2,3-thiadiazole chemistry with the appropriate screening system. Both application methods, nursery box and into-water applications, can be used in rice cultivation. It shows excellent activity against rice blast and also exhibits activity against some rice bacterial diseases. Tiadinil has a favorable toxicological, eco-toxicological and kinetic profile. © Pesticide Science Sociey of Japan