Preliminary Study Of Alarm Pheromone Of The Brown Planthopper, Nilaparvata Lugens (Stal)

This paper was aimed to study alarm behavior and alarm pheromone of BPH。 Y-tube olfactometer was used to examine whether volatiles released by BPH being preyed on by dwarf spider could elicited escape behavior of colonymates; Then, the volatiles were isolated and analysed. At last, solvent extract of the volatiles was examined with Y-tube olfactometer for its effect on BPH. The results were as follows:(1) Behavioral response of the brown planthopper, Nilaparvata lugens, to the volatile substance of the same kind of insects attacked by dwarf spider, Erigonidium graminicolumBehavioral response of the brown planthopper (BPH), Nilaparvata lugens, to the same kind of insects attacked by dwarf spider, Erigonidium graminicolum, was studied with Y-tube olfactometer in order to verify whether the alarm signal was released to the same kind of insects when BPH attacked by their natural enemies. The results showed that no escape response of BPH nymphs to the chemicals of E. graminicolum, significant escape response of the1st instar nymphs, very significant escape response of the2nd to3rd instar nymphs and no obvious response of the4th to5th to the volatile substance released by the same kind of insects when attacked by E. graminicolum. It was conjectured that E. graminicolum may has weak predatory ability on older nymphs of BPH, or older nymphs may not release alarm signal when they were attacked by E. graminicolum.(2) Isolation and analysis of the volatile substance released by BPH indangrousVolatile substances released by BPH only and BPH attacked by E. graminicolum were extracted with SPME material included PDMS and CAR/PDMS. Empty odor source and BPH only was used as control. Extract was analyzed with GC-MS. The result showed that new substance was released by BPH coexisting with E. graminicolum. The new substance was presumed to be a seven-carbon acyclic compound with an alkenyl and a carbonyl group, according to the mass-spectrogram. In addition, some components were both detected in volatiles of BPH only and BPH coexisting with the spider. They may be contaminant, or alarm pheromone produced as a result of the transmission from plant to odor source, or other pheromones of BPH. Their origin and function should be still determined by further study. (3) Verification of alarm pheromone released by BPH in dangrousBy studying the extract condition of alarm pheromones of BPH, we found a good extract effect of the volatiles extracted with ethyl acetate solvent, a reasonable number of2nd to3th instar nymphs of BPH (300BPH in500mL taste source bottle), suitable extract time for continuous three hours, and extract temperature is15-25℃. Effect of this extract to2nd to3th instar nymphs of BPH was tested with Y-tube olfactometer. The result showed that ethyl acetate extract induce significantly the escape behavior of2nd to3th instar nymphs of BPH. Ethyl acetate solvent was proved to be most effective to extract the volatiles released by BPH, and it was verified that BPH could release alarm pheromones to the same kind of insects when they attacked by E. graminicolum. This compound dissolved in ethyl acetate solvent easily, and its volatile was less than ethyl acetate.