Population Dynamics and Biological Control of Leucoptera malifoliella in Apple Orchards in Hebei Province, China

<i>Leucoptera malifoliella</i> has become a severe leaf-mining pest in Chinese apple orchards, especially under expanding organic and green cultivation practices, with effective management hindered by insufficient contemporary ecological data. To fill this gap, this 2023-2025 study conducted in Shijiazhuang, Hebei, combined field monitoring, morphological analysis, flight mill assays, and parasitoid release trials to clarify the moth's phenology, develop rapid pupal sexing methods, quantify adult flight capacity, and assess <i>Trichogramma dendrolimi</i> biocontrol potential. The results showed five annual generations (overwintering as pupae), peak damage in July-August, and marked generational overlap. A reliable pupal sexing method was established via genital opening morphology. Adult flight peaked at 3 days post-emergence (max distance: 1.223 km), with no sexual dimorphism. Timely <i>T. dendrolimi</i> releases boosted parasitism rates, achieving 23.4-49.6% control efficacy during peak damage, with the parasitism rate positively correlated with efficacy. This study confirms the moth's potential for generational increase under climate warming and medium-distance dispersal capacity, validating <i>Trichogramma's</i> utility and laying a scientific foundation for precise, regionally coordinated ecological management.