Chiang Mai Journal of Science

    Plant resistance to herbivores is a key component of integrated pest management (IPM). Silicon (Si) amendment in rice (Oryza sativa) influences multiple plant defense responses, particularly against phloemfeeding insects like the rusty plum aphid (Hysteroneura setariae). This greenhouse study examined the effects of Si supplementation (calcium silicate, Ca₂SiO₄) at 0%, 2%, and 4% per gram of soil on silicification and aphid infestation. Defense-related enzyme activities—including peroxidase (POD), polyphenol oxidase (PPO), and phenylalanine ammonia-lyase (PAL)—were measured in aphid-infested rice plants with and without Si amendment. Results showed that Si-treated plants exhibited increased silicification and larger silicon cell size in leaf sheaths than untreated plants. Aphid infestation was significantly lower in plants amended with 2% and 4% Si than in non-amended controls. Additionally, POD, PPO, and PAL activities were higher in Si-treated plants than in non-amended aphid-infested plants. These findings suggest that Si supplementation enhances rice resistance to aphids by inducing plant defense responses, offering a promising strategy for sustainable rice IPM.