Essential Element Zn Pollution: A New Abiotic Factor Affecting the Defense of Fraxinus mandshurica and Biocontrol of Arma chinensis against Hyphantria cunea

Abstract Zinc (Zn) pollution is common in pest habitats, but its impact on pest populations has been largely overlooked. This study constructed a Zn-contaminated ecological model comprising “soil-Fraxinus mandshurica-Hyphantria cunea larvae-Arma chinensis nymphs” to comprehensively assess the effects of Zn pollution on the occurrence trend of H. cunea. Results showed that Zn was transferred and biomagnified along the food chain, significantly reducing the H. cunea occurrence trend and energy metabolism. Zn pollution altered the regulatory role of F. mandshurica on H. cunea in three ways: by increasing defense substances, reducing the nutrient content, and enhancing elemental defense levels. Moreover, Zn significantly impaired A. chinensis predatory fitness, predatory function, and search efficiency, mainly because of elevated oxidative damage in nymphs. In conclusion, Zn influences the population dynamics of phytophagous pests by modifying plant defenses and the regulatory capacity of natural enemies, thereby highlighting the ecotoxicological effects of this essential metal.