Rice husk ash-derived nano-silica: A sustainable carrier for Kasugamycin to combat rice blast disease

Nano-sized silicon dioxide (SiO₂ NPs) is widely employed as a pesticide carrier in agricultural systems. However, its high production cost significantly limits large-scale adoption. In this study, we developed an economical and environmentally benign nano-pesticide (KSM@SiO₂) by loading kasugamycin (KSM) onto SiO₂ NPs synthesized from rice husk ash (RHA). The optimized synthesis parameters were determined as follows: 6 h calcination, 1.5 mol/L NaOH, and a SiO₂:KSM mass ratio of 1:2-yielding 25.3 % SiO₂ and a KSM loading efficiency of 16.1 %. KSM@SiO₂ exhibited robust antifungal efficacy against Magnaporthe oryzae, with an EC₅₀ value of 0.19 mg/mL, nearly double the potency of pure KSM (0.35 mg/mL). Electron paramagnetic resonance (EPR) analysis verified the formation of •OH, •O₂^-, and ¹O₂. These reactive oxygen species (ROS) subsequently induced oxidative stress, hyphal disruption, DNA fragmentation, and enhanced membrane permeability. The nanoformulation demonstrated superior leaf adherence, as evidenced by a contact angle of 94.22° and a 20 % improvement in retention compared with free KSM. FITC tracing further confirmed its systemic translocation from roots to leaves within 24 h. Biosafety assessments revealed no adverse effects on rice seed germination or root development. Instead, KSM@SiO₂ promoted antioxidant enzyme activities and exhibited no significant toxicity to earthworms. Economic analysis showed that its production cost was reduced by 72.5 % relative to commercial SiO₂.Overall, this work provides a sustainable and cost-efficient nanocarrier strategy for rice blast management. It also demonstrates a viable route for converting agricultural waste into high-value nano-fungicidal materials, thereby supporting the advancement of circular bioeconomy practices.