Cellulose nanocrystals for crop protection: leaf adhesion and controlled delivery of bioactive molecules

The development of new approaches for pesticide delivery is a most relevant subject in the area of crop protection, which typically involves relatively high pesticide dosing combined with low deposition and limited biosafety. Herein, we investigate a pesticide carrier system based on plant-derived, eco-friendly cellulose nanocrystals (CNCs) modified with beta-cyclodextrin (beta-CD) and tannic acid (TA). A broad-spectrum and widely used pesticide, fenitrothion (XCM), was shown to bind to the carrier through hydrophobic and hydrogen bonding interactions and Cu2+ coordination, enabling pH-controlled delivery. The high axial aspect of CNCs and surface features endowed by beta-CD binding facilitated contact and enhanced the deposition efficiency on the foliage. The tannic acid further improved wetting, adhesion and retention on leaves (1.8-fold higher than TA-free systems). The bioactivity tests showed efficient antifungal (74%) and insecticidal (97%) effects along with excellent biosafety, highlighting the introduced carrier for its promise in the area of pesticide delivery.