Relative Effects of Demethylation-Inhibiting Fungicides on Late Leaf Spot of Peanut

Field experiments were conducted in Tifton, GA, in 2007, 2008, and 2016, and in Plains, GA, in 2016 to examine the effects of various demethylation-inhibiting (DMI) fungicides on late leaf spot (Nothopassalora personata) of peanut (Arachis hypogaea) and to determine the relative efficacy of the DMI fungicides compared with tebuconazole and the protectant fungicide chlorothalonil. In all trials, leaf spot control provided by tebuconazole, metconazole, tetraconazole, propiconazole, and flutriafol was inferior to that provided by chlorothalonil. However, prothioconazole was superior to chlorothalonil for control of leaf spot in all trials. These results indicated that reduced efficacy of tebuconazole for control of late leaf spot coincides with similar reductions in control with most other available DMI fungicides. However, superior leaf spot control obtained with prothioconazole relative to the other DMI fungicides and chlorothalonil implies that efficacy of tebuconazole is not indicative of the performance of all other DMI fungicides on this disease.