Host sex pheromones affect parasitization preference of Trichogramma ostriniae (Hymenoptera: Trichogrammatidae)

Trichogramma ostriniae Pang and Chen (Hymenoptera: Trichogrammatidae) is an important egg parasitoid for the control of lepidopteran pests like Ostrinia furnacalis (Guenée) (Lepidoptera: Crambidae) and Chilo suppressalis (Walker) (Lep.: Crambidae). While host sex pheromones are known to attract parasitoids, their influence on the parasitization preference of Trichogramma species has been less studied. This study developed and validated a novel 4-choice oviposition selection box specifically designed for assessing volatile-mediated parasitization preferences of minus parasitoids like T. ostriniae. Positive control assays confirmed the device allowed random parasitism without bias and established 1 h as the optimal exposure time. Using this device, we investigated whether synthetic sex pheromone blends of O. furnacalis and Ch. suppressalis, and their corresponding commercial trap lures, influenced T. ostriniae parasitization behavior. The results showed that T. ostriniae females significantly preferred oviposition sites associated with both host sex pheromones at 1 μg/μL and with the commercial trap lures over sites associated with solvent controls. This preference was confirmed in seminatural oviposition selection cages containing maize plants (Zea mays L.) (Poales: Poaceae). Our findings demonstrate that T. ostriniae females utilize host sex pheromones as kairomones to locate the potential area of the host female moths, effectively increasing the encounter rate and subsequent parasitism of host eggs. This study provides new insights for developing integrated biological control methods that synergize T. ostriniae with host sex pheromones, enhancing biological control efficacy while improving host location.