Silicon dioxide in the defense indction of soybean against Spodoptera frugiperda
Silicon can increase the natural defence of plants against stresses including herbivorous insects. Silicon dioxide (SiO2) is one of the forms of silicon, and despite its wide use in the industrial sector, its use in agriculture is still poorly adopted. The aim of this study was to evaluate the effectiveness of foliar application of SiO2 in inducing defence against Spodoptera frugiperda in soybean. The experiments were conducted in a completely randomised design with four treatments (0%, 1%, 2.5%, and 5% of SiO2). The effect on cannibalism, biological parameters (mortality, duration of the larval stage, duration of the pupal stage and pupal weight) and wear on the mandible of S. frugiperda were evaluated. The foliar silicon content was also determined. The supply of SiO2 prolonged the duration of the larval and pupal stages of the S. frugiperda by 0.56 and 0.17 days for each 1% of SiO2 applied, respectively. The use of SiO2 at 5% increased the mortality rate of caterpillars in the larval stage by approximately 25%. There was no effect of SiO2 application on cannibalism and weight of S. frugiperda pupae. There was wear on the caterpillars' jaws in the third and fourth instar at the highest SiO2 concentration. The application of SiO2 promoted greater accumulation of silicon in soybean leaves. It is concluded that the foliar application of SiO2 affects the biological performance of S. frugiperda through the induction of defence in the soybean crop and presents itself as a promising strategy in integrated pest management programmes.
