Olfactory responses of predatory bug, Orius albidipennis, and Parasitoid Wasps, Eretmocerus mundus and Eretmocerus eremicus, to Bemisia tabaci and competitor natural enemies

Cotton whitefly, Bemisia tabaci (Gennadius), is one of the most important pests of field crops, vegetables, and ornamental plants. Parasitoid wasps, Eretmocerus mundus Mercet and Eretmocerus eremicus Rose and Zolnerowich, as well as predatory bug Orius albidipennis Rueter are natural enemies which are used as biocontrol agents to control B. tabaci and play a critical role in reduction of chemical insecticide application. In this study, experiments were carried out using a Y-tube olfactometer to determine the impact of volatiles emitted from leaves infested by B. tabaci on attraction of natural enemies. Moreover, the effect of presence of one natural enemy on attraction or repellency of another natural enemy was studied. Results of olfactory responses showed that infested cucumber leaves were more attractive for all species of natural enemy species, O. albidipennis, E. mundus and E. eremicus, than healthy leaves. The results also showed that O. albidipennis avoided leaves that both species of parasitoid wasps coexist on them. However, presence of O. albidipennis on the leaves as a competitor did not affect the attraction of the parasitoid wasps to infested leaves. Induced reactions in damaged plants increase their resistance to invasive pests. These changes can affect the reactions of all organisms around the plants including herbivores, pollinators, natural enemies, and even other plants nearby. Previous research confirms our results on attraction of natural enemies to plants injured by B. tabaci. Avoidance of O. albidipennis of patches containing parasitoids may be due to escape from intraguild predation or other reasons like low quality food in such patches. On the other hand, in this study both parasitoids preferred leaves containing O. albidipennis and whitefly nymphs to leaves with only whitefly nymphs. There is a hypothesis that female parasitoids should not avoid the polyphagous predators because they will lose many oviposition locations, as the number of polyphagous predators is too far in agroecosystems. This theory is corresponding well with the results of our study.