While soybean is one of the main crops produced in Brazil, it can have severe losses of production due to the incidence of Asian rust caused by the fungus Phakopsora pachyrhizi. Fungicide application is the main method of rust control. In order to reduce application costs, there has been a trend to reduce spray volumes. The purpose of this study was to evaluate the effectiveness of applying the commercial mixture trifloxystrobin + prothioconazole (Fox®) in different spray mixture volumes on the leaves of the lower, middle and upper thirds of soybean plants. Rust control and yield were evaluated under high disease pressure. The spray volumes evaluated were: 50 L ha⁻¹, 100 L ha⁻¹, 150 L ha⁻¹, 200 L ha⁻¹, 300 L ha⁻¹ and 400 L ha⁻¹ in three fungicide applications at the R1, R4 and R5.5 stages using the TT 11001 tip from Teejet® at a working pressure of 5 bar. There was a direct relationship between the increase in spray volume and spray coverage levels in the upper, middle and lower thirds of soybean plants. The increase in spray volume provided greater leaf coverage but had no effect on rust control or yield. The commercial mixture trifloxystrobin + prothioconazole (Fox®) can control rust at spray volumes of 50 L ha⁻¹ under favorable environmental conditions.

大豆是巴西的主要农作物之一，但由于真菌菜豆（Phakopsora pachyrhizi）引起的亚洲锈病的发生，大豆可能会遭受严重的生产损失。杀菌剂的应用是防锈的主要方法。为了降低应用成本，存在减小喷雾量的趋势。这项研究的目的是评估在大豆植物的下部，中部和上部三分之一的叶片上，以不同喷雾混合物体积施用市售混合物三氟杀螨醇+硫代康唑（Fox®）的有效性。在高病害压力下评估了防锈效果和产量。评估的喷雾量为：50 L ha ^-1，100 L ha ^-1，150 L ha ^-1，200 L ha ^-1，使用来自Teejet®的TT 11001吸头，在5 bar的工作压力下，在R1，R4和R5.5阶段在三种杀菌剂应用中分别使用300 L ha ^-1和400 L ha ^-1。大豆植物上部，中部和下部三分之二的喷雾量增加与喷雾覆盖水平之间存在直接关系。喷雾量的增加提供了更大的叶片覆盖率，但对防锈或产量没有影响。在有利的环境条件下，市售的三氟氧菌酯+硫代康唑（Fox®）混合物可在喷雾量为50 L ha ^-1的情况下控制锈蚀。