| Anagrus nilapavatae (Hymenoptera:Mymaridae) is an important biological control agent of rice planthoppers. Flowering plants can provide not only shelters, refuge habitats, non-hosted nutrtion such as nectar and pollen for natural enemies, but also attractive volatile compounds which are tracing cues for natural enemies to find the nutrition sources. Therefore, seeking effective flowering plants and volatile compounds are helpful to parasitic performance of A. nilaparvatae. Abelia grandiflora is a perennial bush plant with long-period of blooming which may provide direct nutrition resource and as host plant for alternative prey of natural enemies. Our studies focus on seeking the attractive plants and odors to the parasitoids, which may lay a foundation for further research on enhancing the natural enemies of rice planthoppers, and devoted to enhance the parasitic biological control ability.1. The distribution and local movement of A. nilaparvatae between rice field and flowering plantsViscous yellow boards were used to investigate the distribution and local movement of the parasitoids between rice field and flowering plants. There were significantly high amount of caught on yellow boards set up around Abellia x grandiflora and Sesame flowering plants on bunds in ecological engineering fields compared with no-flowering plants on bunds in conventional fields. The number of parasitoids moved locally from rice field to flowering plants is more, when compared to the opposite direction in July, the critical period for establishment of biological control agents. In August and September, the main duration of population growth of planthoppers, frequent rice field-forward local movement of the parasitoids was found too, suggesting the existence of "attraction-feeding and backing for ovipositing in rice field" effect. Such effect indicates the ecological engineering have high potential of ecosystem service of biological control.2. The preference of A. nilaparvatae to Abelia grandiflora A Y-tube olfactometer was used for measuring the choice of egg parasitoids to flowering plants odors. By compared with 9 plant species, we found that the flowers of A. grandiflora were significantly attracted to A. nilaparvatae.3. Analysis of volatiles sampled from A. grandiflora flowersBy using the SPME/GC-MS,21 volatile compounds were identified from the flowers of A. grandiflora. Among them a-pinene (22.86%) was the most abundant compound, while a-pinene, carophyllene (18.5%). and β-Pinene (14.06%) as the major ones. The content of terpenoids detected from A. grandiflora is more than 89.14%, while that of benzenoids and fatty acid derivatives as 2.4% and 1.13%, respectively.4. Response of A. nilaparvatae to chemical compoundsThe preference of A. nilaparvatae to the above mentioned 9 main volatile compounds from A. grandiflora were measured by using a Y-tube olfactometer. The results showed that β-pinene and phenylacetaldehyde were the most attractive to A. nilaparvatae.In summary, the present study focused on the behavioral response of A. nilaparvatae toward A. grandiflora and its volatiles compounds. As a volatile and pollen providing plants, A. grandiflora has the potential to enhance the biological control ability. The volatile compounds β-Pinene and phenylacetaldehyde are potential for management of natural enemy by helping developing either attractants for calling A. nilaparvata together or a particular support accompany with beneficial feed. |
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