Abstract:

Based on the analysis of terpene samples in five physiological states of host trees by gas chromatography-mass spectrum, α-pinene has the largest proportion in all states. There are large variations in terpene compositions and their relative contents in stem and branch of healthy Pinus massoniana. With the decline of host pine health, the relative contents of α-pinene significantly decrease and the relative contents of β-pinene significantly increase in stems or branches of baited tree. We conclude that the lower ratio of α-pinene and β-pinene indicates the more declining host health. The contents of α-pinene, β-pinene and β-phellandrene were significantly different between P. massoniana stem and branch in physically damaged states. P. massoniana also has a distinctive terpene composition on the trees damaged by oviposition as well as the up and down part of the stem. In feedingdamaged state, there are large variations in terpene compositions and their relative contents between P. massoniana and Cedrus deodara. The relative contents of α-pinene，β-pinene and β-phellandrene are significantly different in heavily oviposited stem and feeding-damaged branch. The contents of β-pinene and limonene in baited stem after 13 days are higher than those in physically damaged stem after 13 days, but the content of α-pinene varied contrarily. The relative contents of α-pinene and β-pinene in feeding-damaged branch are significantly higher than those in heathy branch, and β-mercene,β-phellandrene and trans-caryophyllene in healthy branch are significantly higher that those in feeding-damaged branch. The relative contents of terpene compositions are significantly different between healthy stem and oviposited stem, except for α-pinene and β-pinene. There are large variations in the relative contents of α-pinene, β-pinene and β-phellandrene in stem or branch between physically damaged, oviposited and feeding-damaged states. In conclusion, α-pinene, β-pinene and β-phellandrene maybe play important roles in regulating the feeding and ovipositing behaviours of Monochamus alternatus Hope. M. alternatus showed a moderate electroantennogram (EAG) response to many volatile terpenes, but there is a significant sexual difference of the relative EAG responses between male and female. The highest EAG response was elicited by β-pinene.

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Key words: Monochamus alternatus, Pinus massoniana, host volatiles, terpenes, electroantennogram, gas chromatographymass spectrum