Chemotactic responses and parasitism of Trichogramma pretiosum after successive generations in Spodoptera frugiperda.

Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae) is an important parasitoid of lepidopteran pests. Its parasitism success is related to its foraging behavior, mediated by kairomones from its hosts. We aimed to evaluate the chemotactic responses and parasitism of T. pretiosum from Ephestia kuehniella (Zeller) (Lepidoptera: Pyralidae) eggs as well as the parasitoid maintained for three generations in Spodoptera frugiperda (Smith) (Lepidoptera: Noctuidae) eggs. Chemotactic responses of T. pretiosum from both hosts were evaluated in a dual choice olfactometer. Females were submitted to a choice between washed vs. unwashed eggs of E. kuehniella or S. frugiperda, as well as to unwashed eggs of both hosts. Egg extracts of both hosts were also contrasted with hexane and with each other. Parasitism of T. pretiosum exposed to eggs of the two species was also evaluated. Females from E. kuehniella were more attracted to odors from eggs of this host whenever it was present. Third generation parasitoids from S. frugiperda eggs were more attracted to eggs and egg extract of S. frugiperda than to those from E. kuehniella. The highest number of parasitized eggs and emerged parasitoids in S. frugiperda was observed in parasitoids coming from the third generation in this host. Therefore, imaginal conditioning could be an alternative to be considered for T. pretiosum learning before releasing, possibly optimizing its search and parasitism process in S. frugiperda eggs