Variance in Relative Concentration of Induced Volatile Monoterpenes Composition of Pinus tabulaeformis by Dendroctonus valens

The volatiles of the male Dendroctonus valens infected, artificially damaged and control Chinese pine (Pinus tabulaeformis), were extracted with Porapak Q absorbent in headspace absorption method for eleven consecutive stages. The chemical constituents of the volatiles were analyzed by GC and GC-MS and their relative contents of monoterpenes were determined by the normalized peak areas. The infected pines contained significantly higher ratios of (+)-α-pinene (more than 90%) and myrcene, but lower levels of (+)-3-carene, (-)-β-pinene, camphene and limonene, when compared to the control and damaged trees. The abundance of (+)-3-carene (less than 4%) in the infected pines was lower than that in control and damaged pines. However, the abundance of (+)-3-carene in damaged pines reached to the level of control pines gradually from a lower level. The abundance of (-)-β-pinene and limonene was similar in different treatment pines, but there were significant differences among them after infected by male accompanied with femal D. valens. Although it is unknown whether D. valens releases pheromone after attacking Chinese pine in China, our results suggest that D. valens might use specific variations of composition of the monoterpenes as chemical cues for host tree selection and population aggregation. Meanwhile, this study has an important significance for explaining resistance mechanism of Chinese pine and improving the monitor and control system for D.valens.