Behavioral response of zigzag ladybird beetle Cheilomenes sexmaculata to the HIPVs induced by cotton aphid, Aphis gossypii

Recent developments in insect science and technology and integrated pest management (IPM) are laying a concrete path for transition from the dreaded chemical-based pest management to biological and biorational-based methods. Herbivore-induced plant volatiles (HIPVs) play an important role in host plant-herbivore-natural enemy interactions and have the potential to enhance the effectiveness of biological and biorational-based controls for integrated pest management (IPM). Synthetic HIPV blends can potentially improve the foraging behavior of predators by attracting them. This study was conducted to explore the emission of plant volatiles under infestation by cotton aphids, Aphis gossypii Glover, and their influence on attraction response of predatory six-spotted ladybird beetle, Cheilomenes sexmaculata (Fab.). Cotton leaf extracts were analyzed by gas chromatography coupled mass spectrometry (GC-MS), and the response of C. sexmaculata to the various extracts was assessed with a Y-tube olfactometer. By comparing the volatile profile of aphid-infested leaf extract with that of uninfested leaf extract, three compounds, namely 3-carene, pentadecane, and alpha-linolenic acid, were identified as aphid-induced HIPVs. However, the abundance of the other three compounds, heptane, 3-hexenal, and alpha-copaene significantly increased upon aphid infestation. At a concentration of 5%, aphid-infested leaf extract had the greatest effect on both female (85.9 +/- 7.6%) and male (80.9 +/- 6.4%) beetles. These results confirmed that HIPVs induced by aphids in cotton could attract C. sexmaculata beetles. Future tests need to be conducted to determine which compounds could be exploited as attractants for C. sexmaculata.