Comparison of Cuprous Oxide and Chlorothalonil Applied Alone and as Tank Mix Partners with Flutolanil or Inpyrfluxam for Management of Late Leaf Spot (Nothopassalora personata) of Peanut

• DOI: 10.1094/php-02-25-0052-rs
• Publication Date: 2025-05-02T15:10:51Z
• Authors: Alana G. Atkinson; Tim Brenneman; Robert C. Kemerait; Emily G. Cantonwine; Albert K. Culbreath

The protectant fungicide chlorothalonil has been used for management of late leaf spot (Nothopassalora personata) of peanut (Arachis hypogaea) for over fifty years. However, recent concerns with regulatory issues in both the U.S. and the European Union have prompted efforts to identify alternatives to chlorothalonil for leaf spot control. Cuprous oxide has shown promise for leaf spot control, but a direct comparison between cuprous oxide and chlorothalonil has not previously been reported. Seven field experiments were conducted in Tifton, GA from 2010 to 2024 in which the effects of cuprous oxide and chlorothalonil on late leaf spot were compared when applied alone. In the experiments conducted from 2022 to 2024, the efficacies of cuprous oxide and chlorothalonil as mixing partners with flutolanil and inpyrfluxam were also compared. In all cases, final leaf spot severity ratings for cuprous oxide applied at 0.93 kg metallic copper/ha (1X) rate were comparable to or lower than those of 1.26 kg a.i./ha of chlorothalonil applied on the same schedule. For leaf spot control, tank mixes of cuprous oxide at either 0.47 kg metallic copper/ha (0.5X) or the 1X rate with flutolanil or inpyrfluxam were similar to or better than respective mixtures that included chlorothalonil 1.26 kg a.i./ha. These results indicate that cuprous oxide has potential as an alternative to chlorothalonil for leaf spot control in peanut, both as a stand-alone treatment and as a mixing partner with flutolanil or inpyrfluxam.