Does Trichogramma australicum Girault (Hymenoptera: Trichogrammatidae) use kairomones to recognise eggs of Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae)?

We tested the oviposition behaviour of female Trichogramma australicum on host eggs and glass beads. No washing by organic solvent or water could effectively remove recognition cues from Helicoverpa armigera eggs. Possible recognition kairomonal materials (accessory gland secretion and lateral oviduct liquid contents of H. armigera) did not have a pronounced effect on stimulating ovipositor probing and drilling by T. australicum. Therefore, we consider that T. australicum females do not depend on chemical cues to recognise their host eggs. We found that deteriorating change in the characteristics of natural host eggs can reduce the acceptance of the host by female T. australicum. This rejection behaviour may allow the wasp to identify unacceptable hosts and oviposit only in hosts of ‘good’ quality.