A review: Phytoliths for insect pest management

Abstract

Phytoliths are inorganic, non-crystalline silica (SiO2) structures that form through the polymerization of monosilicic acid (H4SiO4) absorbed from the soil. These phytoliths play a crucial role in enhancing plant growth and development, especially under challenging environmental conditions. They contribute mechanical support and rigidity to plant tissues, act as a defense mechanism against herbivores, pests, and fungal infections, and also improve water regulation, overall plant growth, photosynthesis efficiency and finally yield. Modern agriculture mainly depends on use of synthetic pesticides for the management of harmful insect pests. Pesticides are found as common contaminants in soil, air, water ecosystems and produce adverse effect on non-target organisms present in various ecosystems. They can harm plants and animals ranging from beneficial soil microorganisms and insects, non-target plants, fish, birds and other wildlife. Silicon is the second most abundant element in the earth crust and silicon soil amendment and foliar application has been shown to enhance plant defenses against insect pests. Silicon-mediated resistance to herbivorous insects and the mechanisms primarily involves formation of physical or mechanical barriers, and biochemical/molecular mechanisms, where silicon (Si) can enhance and prepare plant defense systems against insects. In addition, silicon also known to interact with other plant nutrients and induce the plant resistance against insect pests. A high Si level could influence the availability of other nutrients in plants, such as nitrogen, inducing insects to consume greater quantities of high-Si-treated plants. In addition, a high silica content in plant tissue reduces its digestibility and palatability, consequently slowing the insect growth rate. The role of phytoliths as mechanical barriers, and enhancers biochemical defense pathwaysagainst insect herbivores is elucidated in this review.