Nanopesticides are pesticide formulations in which intentionally designed nanoscale carriers shape how an active ingredient (AIng) is deposited, transformed, and released. These systems can improve retention and efficacy, but carrier complexity introduces challenges: nanomaterials can transform in real soil–water matrices, reshaping exposure and risk. These processes are hard to quantify because test protocols and risk assessment frameworks for nanopesticides remain underdeveloped. In this review, we relate design choices across major carrier families—including polymer and lipid particles, nanoemulsions, porous inorganic carriers, and bio-based nanomaterials—to transformations in soil–water systems. We then connect these transformations to ecotoxicological evidence across key non-target taxa. We also address a central “measurement gap” in current risk assessment. Many standard tests were developed for dissolved chemicals. As a result, they do not capture (i) particle stability in realistic matrices, (ii) particle-bound versus dissolved (and ion-released) forms, or (iii) time-resolved exposure. Finally, we propose a Safe-and-Sustainable-by-Design roadmap that prioritizes low-hazard materials, predictable degradation, life-cycle thinking, and staged data generation to enable scalable, field-relevant adoption.

The practical efficacy of Azadirachtin (AZA)—a botanical insecticide valued for its strong antifeedant activity—is often undermined by its poor environmental stability, arising from rapid photolysis and thermal decomposition. Herein, amino-modified mesoporous silica nanoparticles (MSNs) were employed as nanocarriers to encapsulate AZA, yielding the AZA@MSNs−NH₂ nanoinsecticide. Under UV irradiation (254 nm), the degradation rate of AZA@MSNs−NH₂ was more than 35% lower than that of commercial AZA after 24 h of exposure. In biosafety tests, MSNs at 50–800 mg/L enhanced cotton seed germination and seedling growth, whereas MSNs below 200 mg/L caused no observable harm to zebrafish survival. Free AZA (0.5–10 mg/L) showed limited efficacy in bioassays against Helicoverpa armigera and Apolygus lucorum, reducing larval weight gain only marginally in the former (mortality < 5%) and performing poorly against the latter. In contrast, AZA@MSNs−NH₂ significantly boosted both growth inhibition and lethal effects against both pests, yielding > 80% growth inhibition and 62.65% corrected mortality for H. armigera, as well as strong lethality toward A. lucorum. Overall, this work confirms that nanoformulation of AZA not only circumvents its physicochemical drawbacks but also boosts its insecticidal performance against cotton pests, supporting the advancement of sustainable cotton pest control.