Silicon for the control of insect herbivores in agronomic crops

Silicon (Si) is considered a non-essential yet beneficial element for plants, playing important roles in growth, productivity, nutrient balance, and responses to abiotic and biotic stresses. Substantial research demonstrates the beneficial effects of Si on plant protection. This chapter synthesizes current knowledge on the role of Si in the control of insect herbivores in agronomic crops, with emphasis on its mechanisms of action, effects on herbivores, and its incorporation into Integrated Pest Management Programs (IPM). Silicon uptake and accumulation vary widely among crop species, and Si-accumulating and non-accumulating plants differ in their responsiveness to Si supplementation. Silicon-mediated resistance operates through enhanced physical defenses, such as tissue strengthening and phytolith deposition, as well as through biochemical and molecular defenses that influence direct toxicity and indirect defenses mediated by herbivore-induced plant volatiles. Beyond plant-mediated effects, Si can directly affect insect herbivores by reducing feeding efficiency, growth, survival, and reproduction, altering host plant preference and oviposition behavior, and potentially compromising insect immune and detoxification processes. Importantly, Si can serve both as a preventive and a suppressive tool in IPM programs. Before infestation, Si can deter herbivore colonization and prime plant defense pathways; after infestation, it can enhance pest suppression and interact synergistically with biological and chemical control tactics. However, the magnitude and consistency of these benefits vary with crop species, pest identity, Si availability, and environmental conditions, highlighting the importance of system-specific research in agroecological systems. Overall, Si is well-positioned for integration into sustainable pest management strategies.