| Aromia bungii Fladermann(Coleoptera: Cerambycidae)is an important wood borer which hosts a variety of fruit and ornamental tree species in Rosaceae family.Due to its concealed life style,it has caused serious damage to fruit industry.Dastarcus helophoroides is a dominant insect natural enemy of longhorned beetles that can effectively control the mature larvae and pupae of the cerambycid.Scleroderma guani Xiao et Wu is also a parasitoid that can effectively control young larvae of some medium to large body of Cerambycidae species.By studying the correlation between two natural enemy species and the volatiles of A.bungii larval frass,the author aims to find out the primary mechanism of two natural enemies locating the host habitat.Moreover,by releasing D.helophoroides and S.guani at different times in the tested peach orchard and comparing with the control orchard,the biological control effect of the combined two natural enemies on A.bungii were studied during two years of field surveying.The main results were as follows.1.Several different solvents were used to extract the larval frass volatiles of A.bungii,then to test the behavioral response of the adults of two natural enemies to the volatile extracts.The results showed that more D.helophoroides adults selected the frass volatiles extracted with0.5g/15 m L n-hexane.Similarly,S.guani exhibited a positive tropism response to the volatiles from larval frass excrement leached with 1g/15 m L,2g/15 m L,3g/15 m L n-hexane,respectively.The adults of two natural enemy species did not show preference to the anhydrous ethanol and acetone extraction of larval frass.Different solvent extraction from the larval body surface of A.bungii were also tested to explore the behavioral response of the two natural enemies.The results showed that D.helophoroides exhibited a positive behavioral response to the volatiles leached from larval body surface with n-hexane,but did not show preference to the volatiles from larval body surface of anhydrous ethanol and acetone extractant.It demonstrated that n-hexane could effectively extract the physiological activity volatiles from the larval frass and the larvae of A.bungii to attract D.helophoroides and S.guani adults.2.Gas chromatography-electroantennograms(GC-EAD)was used to test the antennal response of D.helophoroides to volatiles of larval frass of the A.bungii.The volatiles were identified by both GC-MS and calculating the Kovàts retention index.The results showed that isobazzanene might be the compound aroused the antenna potential response of D.helophoroides.However,it should be more evidence to prove the identification,like compound synthesizes and bioassay.It is important for further study of host searching mechanism of D.helophoroides and biological control of A.bungii in orchards.3.Based on the previous researches in our laboratory,D.helophoroides populations originated from Monochamus alternatus Hope was an effective population in controlling the mature larvae and pupae of A.bungii.The wasp S.guani had a higher parasitism on young larvae of A.bungii.In this study,D.helophoroides and S.guani adults were released sequentially in the peach orchards to control the infection of A.bungii.The results showed that good control effect was obtained on A.bungii.In the case of different management levels in different orchards,the damage degree of peach trees caused by A.bungii decreased,and the peach tree was more healthy.For the orchards with poor management,there were not significant control effect on A.bungii.In conclusion,this thesis found that there were active chemical compounds in the larval frass and larval body surface which could attract parasitoids,and identified isobazzanene might be the kairomone of A.bungii.The joint release of two natural enemies in the peach orchard could control the damage caused by A.bungii to some extent. |
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