Avaliação de fungicidas e da posição do dossel para a análise da severidade de doenças foliares na cultura da soja

Abstract

In soybean cultivation, foliar diseases represent a significant threat to crop productivity. To effectively control these diseases, it is necessary to adopt a combination of appropriate methods, including fungicide management programs. Therefore, the objective was to evaluate fungicide management on soybean cultivars with two degrees of maturity and analyze the best region of the plant canopy for assessing the severity of foliar fungal diseases in soybean culture. We employed a randomized complete block design with four replications, and the treatments were distributed in a double factorial 4x3+1 scheme, comprising five different fungicide application programs and three different regions for disease severity assessment (lower, middle, and upper thirds), applied to both medium and late maturity varieties. We evaluated the area under the disease progress curve, phytotoxicity, defoliation, and yield. The results underwent analysis of variance and, when significant, were subjected to Tukey's test (p<0.05). There was no significant interaction between treatment and analysis region factors for both soybean varieties. All management programs reduced the severity of septoria leaf spot in the medium maturity cultivar. Management programs did not interfere with the yield of both cultivars. The analysis of disease distribution along the plant revealed a higher severity in the lower third, emphasizing the importance of directing attention and control efforts to this region in soybean cultivation.