Fungicida e ativador de defesa no controle da ferrugem asiática, na produção e na qualidade das sementes de soja

Abstract

Among the main diseases that are currently occurring in soybean crops, soybean rust has become a major problem for agribusiness in producing countries. The disease control measures includes several joint actions, being the application of fungicide an effective way to minimize the effects of the disease. Besides these products, resistance inductors have been studied as new alternatives for the control. Given this context, this study aimed to evaluate the influence of fungicide application (PrioriXtra) and defense activator (Bion) in the control of rust, as well as the effect of the disease on the physiological quality of seeds. In order to accomplish the study, four soybean cultivars were used, two disease-tolerant and two susceptible. The treatments were the use of Bion, Priorixtra and the combination of both in the dosage recommended by the manufacturer in the amount of 1.2 to 3 applications during the development of the crop and a control with water application. The study was conducted in randomized blocks in factorial 4x10 with 3 repetitions. It was performed evaluation on field of normalized difference vegetation index, productivity, weight of 1000 seeds and in order to evaluate seed quality the following tests were performed: germination, emergence, accelerated aging and health. By the results it was concluded that the fungicide used in conjunction or not with the defense activator is effective in controlling rust and improving the quality of soybean seeds, when used in 3 foliar applications. The use of only defense activator in the maximum of three applications is not effective in controlling rust. The defoliation caused by rust affects considerably the formation of seeds, as well as productivity and also the percentage of germination and emergence and is influenced by cultivar.