Attraction effect of main volatile components from tea shoots and flowers on Sphaerophoria menthastri ( Diptera:Syrphidae) and Chrysopa septempunctata ( Neuroptera:Chrysopidae)
茶梢和茶花主要挥发物对门氏食蚜蝇和大草蛉引诱效应

The Y-olfactometer bioassays showed that the volatiles from tea aphids and tea aphid-damaged tea shoots (PHC) strongly attracted Sphaerophoria menthastri and Chrysopa septempunctata. At the dosage of 10(-4) g x ml(-1), S. menthastri selected geraniol and methyl salicylate from PHC, n-octanol from intact tea shoots (ITS), nerol from tea flowers (P < 0.01), and (E)-2-hexen-1-ol, E-2-hexenal, 1,3,6-octatriene-3,7-dimethyl and linalool from PHC (P < 0.05), while C. septempunctata selected n-octanol and hexanal from ITS (P < 0.05). At the dosage of 10(-2) g x ml(-1), S. menthastri selected hexanal, nerol and benzaldehyde from PHC (P < 0.05), while C. septempunctata selected hexanal, benzaldehyde, geraniol and (E)-2-hexen-1-ol (P < 0.05). The experimental results showed that besides aldehydes and methyl salicylate, geraniol, n-octanol and (E)-2-hexen-1-ol were significantly attractive to the natural enemies. The selective responses of natural enemies were restricted by thresholds. Both dosages of hexanal significantly attracted C. septempunctata. Nerol might be an infochemicals seducing S. menthastri to orient to tea flowers.