Acid-triggered degradation of a silicon-based nanopesticide activates SA-dependent conifer defense against Dioryctria sylvestrella.

Pine forests in northern China are heavily infested by wood-boring insects, the cryptic life cycles of which make conventional control measures ineffective. We addressed this threat with Sp@SNP, a silicon-based nanopesticide synthesized by polymerization of silane monomers, in which spirotetramat (Sp) was physically entrapped at a loading of 19.92%. The resulting 118-nm nanoparticles showed exceptional water dispersibility, rapid plant uptake, and excellent penetration into the insect cuticle. Sp@SNP selectively released its active ingredient, spirotetramat, in an acid-triggered manner, whereas the silicon-based nanocarrier (SNP) activated salicylic acid (SA)-mediated systemic resistance in plants. Integrated transcriptome and metabolome profiling revealed pronounced activation of phenylalanine-phenylpropanoid metabolism, elevated SA signaling, and a 2-5-fold increase in levels of defense enzymes (e.g., peroxidase, superoxide dismutase, phenylalanine ammonia-lyase, and polyphenol oxidase), accompanied by phenolic accumulation. Drone application of Sp@SNP to Mongolian Scots pine (Pinus sylvestris var. mongolica) achieved rapid xylem translocation and increased larval mortality of the pine tip moth (Dioryctria sylvestrella) by 23.6% compared to a conventional spirotetramat suspension concentrate. Our results demonstrate that Sp@SNP is a precise and sustainable method for controlling wood-boring insects that exerts insecticidal effects and induces SA-mediated systemic resistance in pine trees.