Suppression of Leaf Spot Disease in Peanut (Arachis hypogaea) with Chlorothalonil, Copper Salts of Fatty Acid Rosins, and Microionized Sulfur

Abstract

Concern over evolved resistance to fungicides that are quinone outside inhibitors (QOI), demethylation inhibitors (DMI), and succinate dehydrogenase inhibitors (SDHI) and possible restrictions on the use of the multi-site fungicide chlorothalonil for resistance management have increased the need to develop alternatives to current fungicide programs designed to protect peanut (Arachis hypogaea L.) from late leaf spot disease [caused by Nothopassalora personata (Berk. & M.A. Curtis) U. Braun, C. Nakash., Videira & Crous]. Research was conducted in North Carolina to determine the effectiveness of copper salts of fatty acid rosins and microionized sulfur in protecting peanut yield from canopy defoliation caused by late leaf spot disease. In one experiment, chlorothalonil was more effective in protecting peanut from leaf spot disease than copper salts of fatty acid rosins when these fungicides were applied five times on 14-day intervals during the cropping cycle when the pathogen was active. Chlorothalonil decreased defoliation caused by late leaf spot disease when co-applied with a diverse fungicide program consisting of prothioconazole plus tebuconazole, azoxystrobin, and pyraclostrobin compared with these fungicides without chlorothalonil. Copper salts of fatty acid rosins did not affect defoliation with the diverse fungicide program. In a second experiment, defoliation was similar when azoxystrobin or prothioconazole plus tebuconazole were applied alone or with microionized sulfur. Microionized sulfur provided similar protection from canopy defoliation compared with the more diverse fungicide programs.