Combination of fungicides and resistance inducer for the management of asian soybean rust

Between September 2018 and February 2019, an experiment was conducted in Pirapó, Paraguay, to assess the effectiveness of site-specific fungicides (Prothioconazole 17.5% + Trifloxystrobin 15%) and multisite fungicides (Mancozeb 80%), along with a resistance inducer (copper, manganese, zinc, boron, and amino acids), at different phenological stages of soybean to control rust and improve yield. A randomized complete block design was used with 13 treatments and four replications. The treatments varied in the combination and timing of product application. The severity of rust, control efficacy, defoliation, number of pods per plant, 100-grain weight, and yield were evaluated. The site-specific fungicides reduced the severity of rust at all phenological stages, whether applied alone or in combination with other products. No additional benefits were found by mixing multisite fungicides with resistance inducers. Treatments with only Mancozeb or inducer showed greater defoliation. Treatments T6 and T10 presented the highest number of pods per plant, though without statistically significant differences compared to other effective treatments. There were no differences in 100-grain weight, and the highest yields were observed in treatments T5 and T7.