A Pesticide Delivery System for pH/Enzyme Response: Pectin-Coated O-CMCS Nanoparticles Significantly Enhance Control of <i>Cyperus rotundus</i> L.

<i>Cyperus rotundus</i> L. is a globally invasive weed that is difficult to control due to its aggressive underground rhizomes. This study developed a nanocarrier using O-carboxymethyl chitosan (O-CMCS) to encapsulate halosulfuron methyl (HM) and functionalized the surface of the nanoparticles with pectin (PE) to prepare HM@O-CMCS/PE, which significantly improved herbicide delivery in <i>C. rotundus</i>. Compared with traditional HM water-dispersible granules (HM WG), HM@O-CMCS/PE exhibits better adhesion to leaf surfaces. Quantitative analysis results across different groups indicate that the HM content was highest in the HM@O-CMCS/PE group when testing various parts of <i>C. rotundus</i> at different time points. Greenhouse trials demonstrated superior performance: HM@O-CMCS/PE induced leaf chlorosis (day 7) and necrosis (day 15), reducing chlorophyll A (68.17%), chlorophyll B (51.31%), and carotenoids (42.39%) versus WG. Plant height decreased by 15.52%, while underground tuber viability dropped 73.35% due to oxidative stress, disrupted sugar metabolism, and reduced lignin accumulation. Mechanistic studies indicate that HM@O-CMCS/PE utilizes ABC transporters to achieve efficient delivery to tubers. This system also demonstrates environmental safety advantages. In summary, HM@O-CMCS/PE is a highly promising strategy for effectively controlling <i>C. rotundus</i> and has great application potential in weed control.