Chemotactic responses and parasitism of Trichogramma pretiosum (Hymenoptera: Trichogrammatidae) influenced by sweet alyssum, essential oil of lemon eucalyptus, and host-plant components.

Parasitoids depend on chemical cues to locate and parasitize their hosts, and flowering plants and essential oils may enhance this process within conservation biological control (CBC) strategies. This study aimed to evaluate the chemotactic responses of Trichogramma pretiosum (Riley) (Hymenoptera: Trichogrammatidae) females and parasitism rates in the presence of components associated with a Brassica oleracea var. acephala (L.) cropping system: the flowering plant Lobularia maritima (L.) (sweet alyssum), the essential oil of Corymbia citriodora Hook (EOCC) (Myrtales: Myrtaceae), eggs of Plutella xylostella (L.) (Lepidoptera: Plutellidae), and the parasitoid T. pretiosum, tested either individually or in combination. In a double-choice olfactometer, sweet alyssum was attractive to T. pretiosum females, while cabbage exhibited a repellent effect. Host eggs and EOCC, when tested individually, did not attract the parasitoid. The combination of cabbage + eggs increased attractiveness, which was further enhanced by adding EOCC. Laboratory parasitism bioassays showed no differences among the treatments with cabbage, cabbage + EOCC, and cabbage + sweet alyssum, whereas the cabbage + sweet alyssum + EOCC treatment differed significantly. Under semi-field conditions, cabbage alone resulted in lower parasitism compared with the other treatments. Emergence rates were generally high (83% to 90%), except for cabbage + sweet alyssum + EOCC, which showed reduced emergence. Overall, sweet alyssum is highlighted as a valuable companion plant for attracting T. pretiosum, and EOCC showed potential to support the management of P. xylostella, although certain combinations may negatively affect parasitoid performance.