Asian soybean rust (ASR) is the most important disease affecting soybean production worldwide. This study investigated the efficiency of a new source of soluble silicon for ASR control. The treatments used were: plants sprayed with deionized water (control), fungicide (F) (Opera, Basf S.A.), Alpha (also known as “Silício Forte”) (45 g/L) (Verde Agritech Plc, England), and Alpha (45 g/L) + F. Plants (V4 growth stage) were inoculated with Phakopsora pachyrhizi at 24 hours after spraying. At nine days after inoculation, the first, second, and third leaves of each plant were used to evaluate ASR severity, to determine the total chlorophyll (Chl) a+b and carotenoids concentrations, and to obtain the variable-to-maximum Chl fluorescence ratio parameter (F_v/F_m) related to Chl a fluorescence. There were significant decreases of 99, 42, and 99.5% on ASR severity, respectively, for F, Alpha, and Alpha + F treatments in comparison to control. The total Chl a+b concentration was significantly high by 172, 91, and 142% and the concentration of carotenoids was significantly high by 89, 50, and 67%, respectively, for F, Alpha, and Alpha + F treatments in comparison to control. The F_v/F_m was significantly higher for F, Alpha, and Alpha + F treatments (0.81, 0.77, and 0.80, respectively) in comparison to control (0.74). The spray of Alpha was efficient to reduce ASR symptoms and to result in less photosynthetic impairments imposed by fungal infection.