Nitrogen-Mediated Remodelling of Lycium Barbarum Leaf Traits Drives Multimodal Host Selection by Bactericera Gobica

In commercial Lycium barbarum production, excessive nitrogen (N) input is associated with outbreaks of the wolfberry psyllid (Bactericera gobica), yet the mechanisms underlying nitrogen-driven population increases remain unclear. Integrating field surveys, pot experiments, behavioural assays, and multi-omics analyses, we show that N supply links shifts in visual/olfactory cues and phloem nutrition to B. gobica population increase. Across nine plantations in three major production regions, infestation severity increased significantly with nitrogen input. High N (HN) reprogrammed chloroplast and carotenoid pathways, producing deeper leaf greenness and elevated apocarotenoids (α-ionone, (E)-β-ionone, and benzeneacetaldehyde) that increased pre-landing encounters and attraction. Concurrently, HN elevated leaf soluble sugars and improved phloem nutritional quality, enhancing post-landing acceptance and feeding. Demographic assays revealed higher oviposition, nymphal abundance, and adult densities on HN plants. Thus, an HN-induced trait suite-enhanced visual/olfactory cues coupled with superior phloem nutrition-promotes host encounter and fecundity, delineating a multimodal bottom-up pathway from fertilisation to outbreak risk. These results provide a mechanistic rationale for optimising N inputs in L. barbarum production and motivate integrating nutrient management with semiochemical- and vision-based monitoring and trapping to reduce pest pressure.