Behavioral Manipulating Functions Of Non-host Plant Volatiles To Main Tea Pests

The tea geometrid, Ectropis obliqua (Prout)(Lepidoptera: Geometridae) and tea green leafhopper,Empoasca vitis G the (Hemiptera: Cicadellidae) are the most destructive pest insects of tea plantsthroughout the growing areas of this crop causing huge economic losses and the deterioration of thecommercial tea quality. In this thesis, the behavioral manipulating functions of non-host plant volatilesto two tea pests, E. obliqua and E. vitis were studied, the active compounds in the non-host plantvolatiles were identified and their potential repellency effects on E. obliqua and E. vitis were compared,the manipulation mechanism of this semiochemicals were studied. The emission dynamics of thebioactive chemicals from non-host plants with respect to the photoperiod and seasonal period weremonitored, these can provide the theoretical basis of using non-host plants and bioactivesemiochemicals which have behavioral manipulating functions to control main pests of tea plantation.Finally, this research identified whether non-host plants intercropped with tea plants exhibit effectivebehavior-modifying repellency of E. obliqua and E. vitis in the field, and explore that non-host plants,which are nontoxic and safe to organisms and the environment, are suitable for the control of the pestsin tea plantations by means of supplying “push” stimuli.Behavioral responses of adults E. obliqua to the odors of ten different aromatic plants weremeasured by using “Y” shaped olfactometer in the laboratory, and the antifeedant activities andnutritional interfering effect of ten aromatic plant extracts against the3rd-instar larvae were investigatedby leaf disc choice bioassays. The volatile and the methanol extract of Ocimum basilicum, Rosmarinusofficinalis, Corymbia citriodora and Ruta graveolens plants displayed remarkable repellency against thefemale and male adults E. obliqua. The methanol extract of Nepeta cataria, R. officinalis and Salviafarinacea plants had strong antifeedant activities to E. obliqua larvae at the concentration of200mg/mL.The responses of the antennae of female E. obliqua to the compounds were evaluated using gaschromatography-electroantennogram detection. Consistent electroantennographic activity was obtainedfor eight of the volatile compounds from the four aromatic plants: myrcene, α-terpinene, γ-terpinene,linalool, cis-verbenol, camphor, α-terpineol and verbenone. Qualitative and quantitative differenceswere found among the four odor profiles. Among the individual compounds tested, myrcene andverbenone elicited the strongest electroantennographic responses of the females, while the EAGresponses of the males to linalool, cis-verbenol and camphor were the strongest. Two other EAD-activecompounds, α-terpinene and α-terpineol, elicited very low EAG responses. The sensitivities to six of thesingle compounds were significantly different between the two sexes. The EAG responses of E. obliquato the two blends of active compounds were stronger than to the eight individual compounds. Responsesof E. obliqua to active compounds were all positive and dose-dependent. Six of the eight chemicals,myrcene, γ-terpinene, camphor, verbenone and two blend were found to be significantly more effectiveat repelling the moths. The attraction of males and females to the doses of camphor and blend2werepractically null and moths significantly preferred the control arm when the concentrations of thechemicals at the attraction source was104g mL1and higher. Most bioactive compounds were emittedin significant diurnal cycles. The maximal emissions occurred at nightfall, and the minimal emissionsoccurred at noon. Our field results demonstrated that intercropping tea plants with R. officinalis and O.basilicum effectively suppressed E. obliqua infestations in the tea plantation.Intercropping tea plants with L. pedunculata, R. officinalis, C. citriodora and C. tora effectivelysuppressed the populations of E. vitis due to their emission of semiochemicals. The function of non-hostplant volitiles as the “push” components is not only to render the protected resource unsuitable for thetargeted pest via the negative influence of its stimuli on host location and host acceptance but also toimprove the conservation biological control of E. vitis, by attracting their natural enemies, such asspiders, ladybirds and chrysopa. Behavioral responses of adults E. vitis to the odors of differentnon-host plants were also measured by using “Y” shaped olfactometer in the laboratory, The volatile ofLavandula pedunculata, Rosmarinus officinalis, and Catsia tora plants displayed remarkable repellency against the adults E. vitis. By comparing the repellent activity of different VOC mixtures from non-hostplants, we found that both the quality and quantity of the components in the VOCs were responsible forthe differential repellency of the different species and that terpenoids were the most abundantcomponents in the volatile blends. The dominant VOCs in the odor blend of non-host plant volitileswhich have behavioral manipulating functions were1,8-cineole and α-pinene. Among the individualcompounds tested, p-cymene, limonene and1,8-cineole elicited the strongest behavorial responses ofthe adults, and responses of E. vitis to active compounds were dose-dependent. The volitile compoundswere emitted in significant diurnal cycles from different non-host plants with respect to the seasonalperiod. The maximal emissions occurred in spring and autumn, and the minimal emissions occurred insummertime.The odors of different plant essential oils elicited the different behavioral activity of E. obliqua andE. vitis. R. officinalis, Cinnamomum zeylanicum, O. basilicum, C. cyminum, Pelargoniumx asperumshowed the repellent behavioral activity of adult E. obliqua in the behavioral assays. Melissa officinalisand lavandula pedunculata showed attractive effect on E. obliqua. R. officinalis, Perilla frutescens andPelargoniumx asperum also have deterred oviposition for E. obliqua. In the present study, the repellenteffects of fourteen essential oils, including basil, thyme, eucalyptus, peppermint, cumin, cinnamon,ageratum, rosemary, geranium, melissa, citronella, lavender, perilla and palmarosa, were evaluated intheir volatiles against E. vitis. Among the essential oils tested, the most repellent for adult E. vitis wererosemary, geranium, ginnamon and lavender. At1.0μL mL-1, the plant essential oils of cinnamoncaused most repellency (73.3%) of E. vitis. We compared the efficacy of five plant essential oils to repelE. vitis, in the presence of an attractive odour,(Z)-3-hexenyl acetate in a pasture field. It appears thatrosemary, geranium and lavender is a promising thrips repellent which could be used for further testingin a “push-pull” system.Non-host plant volatiles and the active compounds have the behavioral manipulating functions fortwo tea pests, E. obliqua and E. vitis based on the manipulation mechanism of some semiochemicals. Insuch behavior manipulation processes, the variability and stability of semiochemicals are vital. Theemission dynamics of the bioactive chemicals from non-host plants with respect to the photoperiod andseasonal period showed that the behavior-modifying semiochemicals are reliable. Non-host plantswhich intercropped with tea plants would manipulate the distribution and abundance of pests and/ortheir natural enemies for pest control. Non-host plants and bioactive semiochemicals are suitable for thecontrol of the pests in tea plantations by means of supplying “push” stimuli.