Silica-mediated resistance in cauliflower against diamondback moth (Plutella xylostella)

Diamondback moth (DBM) (Plutella xylostella L.) is a destructive pest of cruciferous crops with a high propensity to develop resistance against synthetic insecticides, necessitating eco-friendly management strategies. The present study investigated the insecticidal potential of natural silica against P. xylostella and silica-mediated resistance in cauliflower under greenhouse conditions through pot culture experiments with three treatments, viz., natural silica, azadirachtin 1 % emulsifiable concentrate (EC) (neemazal) and an untreated control. Foliar application of naturalsilica significantly reduced larval survival, recording 68.57 % mortality at 5 days after treatment (DAT), which was statistically comparable to neemazal (77.14 %). Natural silica-treated larvae showed reduced body size, cuticular abrasion, desiccation and eventual death. Biophysical studies using scanning electron microscopy (SEM) confirmed silica deposition in leaf tissues, reinforcing cell walls and inducing mandibular wear in larvae, thereby restricting feeding. Biochemical assays revealed that silica-treated plants exhibited elevated activities of defense enzymes suchas polyphenol oxidase (PPO), peroxidase (PO) and phenylalanine ammonia lyase (PAL), recording 0.19, 0.38 and 0.95 ΔOD min-1 g-1, respectively, along with higher phenolic content (0.71 g 100 g-1 fresh weight), indicating induction of systemic resistance. Safety assessment through a contact filter paper assay revealed minimal effects of silica on honey bee, Apis cerana indica (8.57 % mortality at 48 hr), lower than neemazal (14.29 %). These results demonstrate that natural silica can serve as a promising alternative to synthetic pesticides in controlling P. xylostella and canfunction as a defensive component in integrated pest management by reinforcing induced defenses and enhancing plant resistance.