Ecological Functions Of Tea Plant Volatiles Induced By Three Herbivores

Ectropis obliqua Prout, Myllocerinus aurolineatus Voss and Empoasca vitis Gothe are the main pests of the tea plantation in China, which could reduce the production and deter the quality of tea. In order to reduce the usage of pesticides, screening active vaolatiles was the purpose. The ecological function of herbivore induced tea plant volatiles in the tritrophic system of tea plants, pests and their natural enemies were studied . The results were summarized as follows.Response of Apanteles sp. adults, parasitoid wasp of E. obliqua larvae, to odors emitted from different sources in a Y-tube olfactometer were studied, the results showed clearly that the parasitoid wasp was attracted to tea plants infested by larvae of E. obliqua and artificially-damaged tea plants but not to healthy tea plants. There were 16 chemical compounds elicited the electrophysiological responses from the antennae of Apanteles sp.. Compared with clean air, the parasitoid wasp were significantly attracted to (E)-2-hexenal,(Z)-3-hexenal,(Z)-3-hexen-1-ol,(Z)-3-hexenyl acetate,(Z)-3-hexenyl butyrate,(Z)-3-hexenyl-2-methyl butyrate,(Z)-3-hexenyl hexanoate,linalool,(E)-β-ocimene.Oviposition preference of female E. obliqua between healthy tea plants and plants infested with conspecific larvae were tested, females showed significant preference for ovipositing on conspecific-infested tea plants over healthy tea plants (Z=2.52, P= 0.012). Apanteles sp. displayed equal preference for tea plants with different levels of host-larvae damage in the field. But the rate of parasitization of E. obliqua by Apanteles sp. on tea plants infested with 60 larvae was significantly higher than on plants infested with 90 larvae. Duration of the larval stage, pupal weight and survival rate of E. obliqua larvae reared on healty tea plants did not differ significantly from those of E. obliqua reared on conspecific-infested tea plants. And no significant differences were observed in the performance of parasitoid wasp between lower and higher host-larvae levels. The results suggested that the oviposition preference of E. obliqua females could reduce risk through the encounter–dilution effect.The results of behavioral bioassays revealed that the tea weevil, M. aurolineatus, was attracted to tea plants infested by conspecifics but not to healthy tea plants, conspecific herbivores, or frass from conspecifics. By using GC-EAD and a Y-tube olfactometer, it was confirmed that both males and females were attracted toγ-terpinene, benzyl alcohol, (Z)-3-hexenyl acetate, myrcene, benzaldehyde, and (Z)-3-hexenal. In addition, males could be attracted to (E/Z)-β-ocimene and (E,E)-α-farnesene; and females could be attracted to (E)-4,8-dimethyl-1,3,7-nonatriene, phenylethyl alcohol, linalool, and (Z)-3-hexenol.In tea plantation, Xysticus ephippiafus and Evarcha albaria are predatory spiders of E. obliqua larvae and E. vitis respectively. The two spiders were not preference to control or treatment in first choice. Frequencies of two species in moving into different patches were not different. Nevertheless, spiders spent significantly longer periods of time on patches that contained preys-damaged tea leaves or mechanically-damaged tea leaves. Results showed that the volatiles transferred the information about the preys, and the spiders could increase foraging efficiency by using the air-borne chemical cues to lengthen residence time in foraging patches.Results showed that insect feeding habit could induce different volatiles. Through GC-EAD and behavioral responses, active compounds which to Apanteles sp., E. obliqua and M. aurolineatus were screened. It was proved that two predatory spiders could make up use of volatiles to choose hunting patches. This study provided bases for applying volatile to pest management in tea plantation.