Increase in foliar silicon content reduces defoliation by Spodoptera frugiperda (Smith) (Lepidoptera: Noctuidae) in maize

The effect of silicon (Si) on fitness and leaf consumption of the fall armyworm (FAW), Spodoptera frugiperda (Smith), has been observed in the laboratory, but the effects of Si on damage or defoliation reduction have not yet been determined under field conditions. Here, we evaluated the effects of amendment of soil with Si on defoliation by FAW and crop yield in maize. Two field experiments were carried out, with four doses of Si and a control (no Si amendment). Experiment #1 evaluated 150, 300, 450, and 600 kg of total Si.ha(-1), with natural or manual infestation with FAW eggs, while Experiment #2 tested 600, 800, 1,000 and 1,200 kg of total Si.ha(-1), with natural or manual infestation with FAW larvae. Defoliation reduction was observed with Si increasing in both Experiments #1 and #2. However, reduction was not observed in all evaluations, and it was dependent of infestation (natural and manual) and the time since manual infestation. Reduction in defoliation began at 600 kg Si.ha(-1). In contrast, plant Si content increased linearly with increasing soil Si application. No effect of Si application was observed on maize kernel yield. The increase in leaf Si content reduced FAW defoliation, but it did not affect maize yield from 600 to 1,200 kg.ha(-1) of Si. Amendment of soil with Si can be used as a strategy to optimize integrated pest management of FAW in maize.