LAUSR

ABSTRACT: In recent years, there have been reductions in the efficacy of the fungicidal control of Phakopsora pachyrhizi, thereby hindering the management of soybean rust and compromising crop yield. This study evaluated the effects of incorporating hydrogen peroxide (H2O2) in commercial fungicide formulations on the control of soybean rust. We conducted two experiments, one of which was performed in a greenhouse environment and the other under field conditions. In both environments, we examined the following four control programs using commercial fungicide formulations: (I) azoxystrobin + cyproconazole (quinone outside inhibitor [QoI] + demethylation inhibitor [DMI]); (II) picoxystrobin + cyproconazole (QoI + DMI); (III) pyraclostrobin + epoxiconazole + fluxapyroxad (QoI + DMI + succinate dehydrogenase inhibitor); and (IV) water (H2O) (program without fungicide application), combined with the incorporation of (i) H2O2; (ii) mancozeb (positive control I); (iii) chlorothalonil (positive control II); or (iv) water (H2O) alone. Analyses of infected leaf area and grain yield revealed that the addition of H2O2 to the formulations of DMI and QoI fungicides led to a reduction in disease severity of between 33% and 44% relative to the effects of these products used alone, as well as an increase in yield and SPAD values. The use of H2O2 and multi-site fungicides alone failed to provide effective control of soybean rust. In addition to enhancing the efficacy of disease control, the use of H2O2 associated with commercial fungicide mixtures was shown to be a potential tool for the management of fungicide resistance and reduction in losses from Asian soybean rust.