| The pine bark beetle, Dendroctonus armandi Tsai et Li(Coleoptera: Scolytidae), is an endemic species of our country. D. armandi primarily attacks healthy Pinus armandii Franch aged 30 years or more.Once invaded by this bark beetles,the host would be weak sharply and created the conditions for colonization of other longicorn beetles and pine bark beetles. For above, D. armandi is the pioneer pests of P. armandii, and pose a significant threat to the Qinling Mountain forests. To verify the effects of the host and the nonhost plant volatiles in the host selection process of D. armandi, electroantennography and Y-tube olfactometer were used to test the electroantennographic(EAG) and behavioral responses of D. armandi adults to the nonhost volatiles.It can provide the theoretical basis for the future use of plant volatiles as control means of D. armandi. The results are as follows:(1)To study the specific component composition and relative content of the terpenoid volatile components in the needle and brandch of P. armandi, the volatile components were extracted by solid phase micro-extraction and were analyzed by GC-MS. The results showed that monoterpene volatiles compounds were main ingredients in needle, and accounted for 65.07%. There are myrcene(21.16%,m/m,the same below),(1R)-α-pinene(19.09%), D-limonene(13.01%) and β-pinene(8.20%).The mainly kinds of sequiterpenoids volatiles compounds in needle are(-)-β-cubebene(10.14%) and carypohyllene(9.95%). Conversely, sequiterpene volatiles compounds were main ingredients in brandch, and accounted for 59.41%. There are carypohyllene(13.32%),(-)-β-cubebene(10.46%), humulene(3.55%) and(-)-β-cadinene(7.21%). The mainly kinds of monoterpene volatiles compounds in brandch are(1R)-α-pinene(14.61%), myrcene(4.31%) and(+)-4-Carene(3.35).( 2) All the nonhost volatiles tested including cis-2-hexen-1-ol, 1-hexen-3-ol, trans-2-hexenal, cis-3-hexen-1-ol, benzaldehyde, trans-2-hexen-1-ol, 1-octen-3-ol and 3-octanol could evoke the clear EAG response of the male and female D. armandi at proper dosages.The response intensified with the increasing concentration. When the concentration increased to 100 μg/μL, the EAG response was the strongest.(3)The females and males showed the strongest EAG responses to trans-2-hexen-1-ol and 3-octanol at the concentration of 0.01 μg/μL and 0.1 μg/μL.Instead,The females and males showed the strongest EAG responses to cis-2-hexen-1-ol and cis-3-hexen-1-ol at the concentration of 10 μg/μL and 100 μg/μL. Pass T test, There’s sexual dimorphism available in the EAG response of the D. armandi to the nonhost volatiles.(4)The result of the indoor bioassays showed that six kinds of nonhost volatiles could induced clear avoid displacement effects of D. armandi in proper dosage,except cis-2-hexen-1-ol and trans-2-hexen-1-ol. 3-octanol showed obviously repellent effect(<30%) to D. armandi at the concentration of 10μg/μL.By contrast,cis-3-hexen-1-ol, 1-hexen-3-ol and 1-octen-3-ol caused slightly weak repellent effects(<40%). With the concentration increased to 100 μg/μL, cis-3-hexen-1-ol, 1-hexen-3-ol, 1-hexen-3-ol,benzaldehyde and trans-2-hexenal enhanced the repellent effects, and 1-octen-3-ol significantly. At the concentration of 100 μg/μL,six kinds of nonhost volatiles except cis-2-hexen-1-ol and trans-2-hexen-1-ol could induced clear avoid displacement effects of D. armandi.(5)In field-trapping experiment,significantly more D. armandi were captured by traps baited with the combinations α-pinene and β-caryophyllene;α-pinene, limonene and β-caryophyllene; α-pinene, β-caryophyllene and myrcene; α-pinene, limonene, β-caryophyllene and myrcene than others among the eight core lure, which are certain combined by α-pinene, limonene,β-caryophyllene and myrcene. The common compositions of efficient lure cores are α-pinene and β-caryophyllene. |
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