Influence of tobacco on the behavior, parasitism and mortality of Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae) associated with eggs of Ephestia kuehniella (Zeller) (Lepidoptera: Pyralidae)

Abstract

Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae), is widely used in augmentative biological control programs. However, there is no information on the behavior and biology of this parasitoid in stored tobacco. Thus, this study aims to evaluate the chemotactic response, parasitism, and mortality of females of T. pretiosum parasitizing eggs of Ephestia kuehniella (Zeller) (Lepidoptera: Pyralidae) in the presence of different tobacco types. The chemotactic responses of T. pretiosum females were observed with a double and multiple choice olfactometer. The odors of dry Burley and Virginia tobacco and of Virginia tobacco seedlings were evaluated. Treatments with or without the presence of E. kuehniella eggs were compared. To evaluate parasitism with and without choice, eggs of E. kuehniella adhered to the same tobacco used in the olfactometer. The eggs of E. kuehniella were offered to a female of T. pretiosum for 2 h, with adult parasitoid mortality recorded. In double-choice olfactometer there was no attraction of T. pretiosum females to the odors of the different types and classes of dry tobacco evaluated when compared to the control (air). Only tobacco seedlings and E. kuehniella eggs attracted the parasitoid. Females of T. pretiosum preferred tobacco infested with host eggs regardless of the type and class of tobacco. In multiple-choice olfactometer T. pretiosum females spent the same time in the area of the arms containing tobacco as in the area of arm containing control (air). The percentage of apparent parasitism of T. pretiosum varied according to the surface on which the host's eggs adhered. Although females of T. pretiosum responded positively to the host's volatiles, even with the presence of dry tobacco, when they came into direct contact with some types and classes of tobacco there was no parasitism.