Silicon - A Potential Alternative in Insect Pest Management for Sustainable Agriculture

Defenses of direct and indirect means are used by plants in order to protect themselves from pest invasion. Direct defense entails biophysical, biochemical, molecular and nutritional barriers that have an impact on herbivores ability to feed grow and survive. Indirect defense entails the emission of mixture of volatile blends referred as Herbivore Induced Plant Volatiles (HIPVs) which attract the natural defenders of the insect pests. These defense-oriented tactics utilized by the plants are strengthened if they are given silicon (Si). Si is absorbed by plants as silicic acid, which they draw in as phytoliths to boost their physical defense. Upon a pest attack, silicon deposited in plant tissue is intensified. In addition, Si increases the protein activity and gene expression which are attributed towards inducing the plant defense and enhancing the building-up of secondary metabolites, hence activates molecular and biochemical defenses. Additionally, Si is essential for both direct and indirect defense mechanisms mediated by phytohormones. Silicon's role in insect defense is more obvious, but the practical applications related to crop protection studies have garnered less attention. This review focuses on the underlying mechanism of different forms of Si in strengthening host plant resistance against insect herbivores.