Uso de volumes de calda para aplicação de fungicidas sobre o progresso da ferrugem asiática e produtividade da soja

Abstract

Asian soybean rust is an aggressive disease that can cause losses of up to 100% of the crop, due to defoliation. The control of this phytopathology is carried out with the use of fungicides, considering the choice of the best volume of spray solution for an adequate deposition of the fungicide in the leaves. The objective of this work was to evaluate the progress and control of Asian soybean rust by the application of fungicides in different spray solution volumes and the effects on crop productivity. The experiment was conducted at the Federal University of Fronteira Sul - Campus Erechim, Rio Grande do Sul – Brazil, in the 2018/19 crop season, in a randomized complete block design (RCB). The treatments were arranged in a 2 x 4 factorial scheme (soybean cultivars x spray solution volumes), with four replications. The evaluated cultivars were BMX Ativa RR and DM 53i54 RSF IPRO and the fungicide volumes were: 0 L ha-1 (control); 100 L ha-1; 150 L ha-1; and 200 L ha-1. The application stages and their fungicides used in all treatments (except the control) were: V6) bixafem + prothioconazole + trifloxystrobin (62.2 + 87.5 + 75 g i.a. ha-1); R1) bixafem + prothioconazole + trifloxystrobin (62.2 + 87.5 + 75 g i.a. ha-1); R5.1) trifloxystrobin + cyproconazole (32 + 75 g i.a. ha-1) + mancozeb (750 g ha-1); and R6) trifloxystrobin + cyproconazole (32 + 75 g i.a. ha-1) + mancozeb (750 g ha-1). The efficiency of the spray solution volumes for fungicide application was evaluated by estimating the area under the disease progress curve (AUDPC) and the effect on the control (%) of the disease. The yield components (number of pods per plant and weight of thousand grains, g) and productivity (kg ha-1) were also quantified. It can be concluded that, according to the increase in the volume of fungicide spray solution applied, there is an improvement in the control of Asian soybean rust, in both cultivars evaluated, as well as productivity.