Smart release biofumigant: temperature-regulated delivery of clove essential oils from diatom-based nanocarriers for store grain pest control

Existing fumigants such as essential oils or synthetic chemicals are limited by high volatility, health impact, instability, and reduced efficacy in stored grain management. These limitations necessitate the development of controlled-release, temperature-responsive alternatives. This study investigates the potential of clove oil (CEO), encapsulating in amine-functionalized diatom silica subsequently capped with a starch-based thermal-responsive polymer to formulate a controlled-release biopesticide (DF-APTES-30-CEO-300-Temp-Cap) against store grain pest Oryzaephilus surinamensis . Successful functionalization, CEO loading and temperature-sensitive capping were confirmed by comprehensive analysis like carbon-hydrogen-nitrogen analysis, fourier transform infrared spectroscopy, thermogravimetric analysis, surface area analysis, and zeta potential. The loading efficiency of the CEO in the DF-APTES-30-CEO-300-Temp-Cap was found to be approximately 37%. The DF-APTES-30-CEO-300-Temp-Cap exhibited strong fumigant activity against O. surinamensis , achieving 100% mortality at 500 mg L − 1 (air) with temperature-dependent efficacy significantly enhanced at 40 °C (100% mortality at dose 31.25 mg L − 1 (air) after 6 h). The LC 50 value decreased from 124.71 mg L − 1 (air) at 20 °C to 35.62 mg L − 1 (air) at 30 °C, and further to complete mortality at 40 °C within 6 h across all concentrations. The invitro assays confirmed that acetylcholinesterase inhibition was the primary mode of action. This is the first time where diatom-based cargo was used for an environmentally responsive system with control release, offering a potential alternative to chemical based fumigants for stored grain pest management.