Duration of protection of peanut from late leaf spot disease by pydiflumetofen

Late leaf spot disease [caused by Nothopassalora personata (Berk. & M.A. Curtis) U. Braun, C. Nakash., Videira & Crous] and southern stem rot (caused by Athelia rolfsii Sacc.) are economically important diseases in peanut (Arachis hypogaea L.) in North Carolina. Fungicides are often applied on a 14-day schedule when these pathogens are active during the cropping cycle to protect peanut yield. The fungicide pydiflumetofen has been shown to provide protection from leaf spot disease for longer than 14 days and is labeled for protection for 28 days. However, efficacy for this length of protection has not been documented in North Carolina. Research was conducted from 2019 to 2022 in North Carolina to compare incidence of leaf spot and canopy defoliation when chlorothalonil plus tebuconazole were applied approximately 21, 28, and 35 days after pydiflumetofen was co-applied with flutolanil or the commercial mixture of azoxystrobin and benzovindiflupyr. Pydiflumetofen does not control southern stem rot whereas flutolanil and azoxystrobin plus benzovindiflupyr do control this disease. Applying chlorothalonil plus tebuconazole 21 or 28 days after pydiflumetofen combinations was equally effective in protecting peanut from yield loss. In some cases, yield was lower when chlorothalonil plus tebuconazole were applied 35 days after pydiflumetofen combinations or when follow up fungicide was not applied. These data suggest that farmers in North Carolina can apply pydiflumetofen and expect 28 days of protection from late leaf spot. However, suppression of disease and peanut yield decreased in some cases when chlorothalonil plus tebuconazole does not occur until 35 days after pydiflumetofen combinations were applied.