Olfactory Responses of Frankliniella occidentalis and Orius similis to Volatiles from Houttuynia cordata: Implications for Thrip Management

Thrips can be attracted or repelled by volatiles from different host plant species. <i>Houttuynia cordata</i> is a common plant species with a strong, offensive smell, and few pests have been detected on this plant. Here, the olfactory responses of <i>Frankliniella occidentalis</i> to <i>H. cordata</i> volatiles were tested using electroantennography (EAG) and behavioral bioassays in different types of olfactometers, and the behavioral responses of <i>Orius similis</i>, a natural enemy of <i>F. occidentalis</i>, to the related main volatile compounds were also evaluated. Y-tube olfactometer bioassays showed that <i>F. occidentalis</i> performed negative responses to <i>H. cordata</i> volatiles. Decanal (47.21%), 1-decanol (11.02%), dodecanal (7.13%), <i>β</i>-myrcene (5.12%), and decanoyl acetaldehyde (3.76%) were the more abundant components in the <i>H. cordata</i> volatile profile in gas chromatography-mass spectrometry analysis. EAG recordings showed that the antennae of female thrips could perceive these five compounds at a wide range of concentrations. In six-arm olfactometer bioassays, <i>F. occidentalis</i> exhibited negative responses to decanal, dodecanal, and decanoyl acetaldehyde at various doses but performed positive responses to 1-decanol and <i>β</i>-myrcene at certain doses. Furthermore, decanal, dodecanal, and decanoyl acetaldehyde at all concentrations showed no significant influences on the behavioral responses of <i>O. similis</i>. According to the results above, <i>H. cordata</i> can be a repellent plant species to <i>F. occidentalis</i>, and decanal, dodecanal, and decanoyl acetaldehyde show great potential for development as repellents for the control of <i>F. occidentalis</i>. In short, our results suggest that an integrated pest management system combining <i>H. cordata</i>-derived biopesticides with releases of the predator <i>O. similis</i> could effectively control <i>F. occidentalis</i>.