Análise epidemiológica e eficácia de fungicidas no controle de doenças foliares na soja em diferentes épocas de semeadura nas safras de 2019/2020 a 2021/2022

Abstract

The optimization of soybean yield potential associated with cost reduction, especially through the use of crop protection inputs, is a constant challenge in agriculture. In this way, the hypothesis of this study was based on the fact that the sowing time (September to December) may influence the incidence and severity of powdery mildew (Microsphaera diffusa) and Asian soybean rust (Phakopsora pachyrhizi), as well as the efficacy of different fungicides. Thus, the objective was to evaluate the epidemiology of these diseases and the performance of crop protection products over three consecutive seasons (2018–2021), covering four sowing periods (September, October, November, and December) in the municipality of Arapoti-PR. The experimental design was randomized blocks, with 4 replications. Eight fungicide treatments were evaluated: [(Prothioconazole 87.5 g L−1 + Trifloxystrobin 75 g L−1 + Bixafen 62.5 g L−1) + Mancozeb 1125 g Kg−1]; [(Prothioconazole 70 g L−1 + Trifloxystrobin 60 g L−1) + Mancozeb 1125 g Kg−1]; [(Pyraclostrobin 99.9 g L−1 + Fluxapyroxad 50.1 g L−1) + Mancozeb 1125 g Kg−1]; [(Azoxystrobin 60 g L−1 + Benzovindiflupyr 30 g L−1) + Mancozeb 1125 g Kg−1]; [(Tebuconazole 95.7 g L−1 + Metominostrobin 63.8 g L−1) + Mancozeb 1125 g Kg−1]; [(Cyproconazole 24 g L−1 + Picoxystrobin 60 g L−1) + Mancozeb 1125 g Kg−1]; [(Azoxystrobin 90 g Kg−1 + Mancozeb 1350 g Kg−1 + Cyproconazole 60 g Kg−1)], in addition to a control treatment. The progression of powdery mildew and soybean rust severity was monitored in each sowing period using the respective assessment scales. Advancing the sowing to September, combined with fungicide application, reduced damage from powdery mildew and rust, resulting in higher crop productivity. Some fungicides were more specific for powdery mildew control, such as fluxapyroxad (50.1 g ha−1) + pyraclostrobin (99.9 g ha−1), while others were more specific for soybean rust, such as tebuconazole (95.7 g ha−1) + metominostrobin (63.8 g ha−1). Other formulations, such as bixafen (62.5 g ha−1) + trifloxystrobin (75 g ha−1) + prothioconazole (87.5 g ha−1), showed a broader spectrum of action. Yield was higher in the September and October sowing periods compared to November and December. The use of fungicides to control soybean diseases ensured the maintenance of the crop’s yield potential, showing control efficiency greater than 48% for powdery mildew and 70% for soybean rust.