Efficacy of fungicides for controlling Macrophomina spp. in melon plant

This study assessed the efficacy of five active ingredients (boscalid, carbendazim, cyprodinil, fluazinam, and fludioxonil) at five concentrations (0.01, 0.10, 1.00, 10.00, and 100.00 mg/L a.i.) against nine Macrophomina isolates (M. phaseolina: CMM1556, CMM4748, and CMM4764; M. pseudophaseolina: CMM2163, CMM4815, and CMM4767; and M. euphorbiicola: CMM2158, CMM4868, and CMM4867). We evaluated daily mycelial growth, growth inhibition percentage, and the effective concentration that inhibits 50% of the radial mycelial growth (EC₅₀). Additionally, the in vivo impact of fluazinam and fludioxonil on the incidence and severity of root rot and vine decline, as well as melon plants biometrics, were determined. Increasing fungicide dose resulted in a higher percentage of mycelial growth inhibition, with the most favorable outcomes observed at 100.00 mg/L a.i. for all tested products. Overall, the Macrophomina isolates exhibited greater tolerance to boscalid (EC₅₀ = 13.40 mg/L a.i.), followed by cyprodinil (EC₅₀ = 1.18 mg/L a.i.), carbendazim (EC₅₀ = 0.05 mg/L a.i.), fluazinam (EC₅₀ = 0.03 mg/L a.i.), and fludioxonil (EC₅₀ = 0.03 mg/L a.i.). The latter two demonstrated high efficacy in vitro. While none of the products achieved complete control of the fungus in vivo, the lowest incidence and severity of root rot and vine decline in melon plants were 28.57% and 0.29, respectively, in plants inoculated with M. euphorbiicola and treated with fludioxonil. For the other species and isolates, fluazinam exhibited better control, resulting in reduced mass loss and root length.