Low Natural Parasitism of the Invasive Halyomorpha halys Versus Strong Native Suppression of Palomena prasina: Evidence from a Three-Year Survey in Northwestern Türkiye

This study assessed the parasitism rates and species composition of egg parasitoids associated with <i>Palomena prasina</i> and <i>Halyomorpha halys</i> in Northwestern Türkiye, one of the country's main hazelnut production areas. Between 2022 and 2024, a total of 15,051 <i>P. prasina</i> eggs and 8490 <i>H. halys</i> eggs were collected from 65 hazelnut orchards and neighboring fruit orchards in Northwestern Türkiye. Egg masses were maintained under laboratory conditions, and emerging parasitoids were identified using morphological and molecular methods. The total parasitism rate on <i>P. prasina</i> was 17.39%, primarily caused by <i>Trissolcus belenus</i> (42.51%), <i>Telenomus turesis</i> (26.47%), <i>Trissolcus cultratus</i> (23.95%), <i>Telenomus truncatus</i> (6.80%), and <i>Anastatus bifasciatus</i> (0.27%). In <i>H. halys,</i> the total parasitism rate was 1.98%, and all parasitoids that emerged were identified as <i>T. belenus</i> (26.19%), <i>T. truncatus</i> (16.67%), and <i>A. bifasciatus</i> (15.48%). The highest discovery (24.88%) and exploitation efficiency (89.83%) for <i>P. prasina</i> were observed for <i>T. belenus</i>. Although native parasitoids are generally considered ineffective against <i>H. halys</i> due to evolutionary mismatch, their natural parasitism on <i>P. prasina</i> eggs is promising for long-term management. The findings clarify parasitoid composition and natural parasitism patterns, demonstrating that conserving and augmenting native parasitoids can contribute to more sustainable management and reduced insecticide dependence in Turkish hazelnut orchards.