Biological properties of flutianil as a novel fungicide against powdery mildew.

Flutianil, chemically characterized as a cyano-methylene thiazolidine, showed antifungal activity against powdery mildew on various crops but not any other plant pathogens tested. Flutianil showed high residual and translaminar activities and rainfastness against Podosphaera xanthii. It also exhibited curative activity against P. xanthii on cucumber at an extremely low concentration of 10 mg/L. There was no cross-resistance between flutianil and other existing fungicides. Morphological studies revealed that flutianil did not inhibit the early infection behavior of Blumeria graminis f. sp. hordei i.e., conidium bursting, primary and appressorial germinations, appressorium development and hook formations, but it did inhibit haustorium formation and further fungal development. Nutrient absorption by haustoria and subsequent secondary hyphal elongation was inhibited by flutianil but not by the fungicide that showed a similar inhibitory pattern up to the haustorium formation stage of the infection process. These findings suggest that flutianil might have a novel mode of action. © Pesticide Science Society of Japan 2020. This is an open access article distributed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) License (https://creativecommons.org/licenses/by-nc-nd/4.0/).