Sensilla And Behavioral Responses Of Adults Of Semanotus Bifasciatus (Coleoptera: Cerambycidae) To Volatile Compounds Of Platycladus Orientalis

Juniper bark borer,Semanotus bifasciatus Motschulsky(Coleoptera:Cerambycidae)is one of the most destructive insect borers of cypress trees, such as Platycladus orientalis. In recent years, old cypress trees protection, forest resources and ecological environment have been threaten by S.bifasciatus in northern China. Through the study on the fine structure of chemosensilla in the head of S.bifasciatus, plant volatiles dynamic headspace sampling and Purge and Trap and GC-MS-MS, as well as insects physiology method, insects behavior method, and other research methods were used to confirm the mechanism of host selection of S.bifasciatus and plant volatiles effect, Which can be taken as a theoretical support on the developing of the plant lure agents and supporting the continued control technologies of S.bifasciatus.The main results showed as follows.1. The fine structure of chemosensilla in the head of S. bifasciatus was first studied. Eight types of sensilla were on the antenna and in labialpalpi and maxillarypalpi of S. bifasciatus.There were 6 types on its antenna, including sensilla chaetica, sensilla trichodea, sensilla basiconca, sensilla styloconica, sensilla campullacea and Bobhm bristles.Its labialpalpi possessed of sensilla chaetica, sensilla gemmiformium, sensilla placodea, sensilla styloconica and Bobhm bristles. Only sensilla chaetica are in its maxillarypalpi. The types, numbers and distribution of sensilla on the antenna and in labialpalpi and maxillarypalpi of male and female S. bifasciatus are almost the same the numbers and types of sensilla from the base of the scrape to the whip of flagellomeres peripherally gradually increased. The types and numbers of sensilla on the antenna and in labialpalpi and maxillarypalpi of male and female adult S. bifasciatus are different. Sensilla chaetica tactile feel with the functions of mechanical stimulation, sensilla trichodea bear smell function, perhaps feeling terpenes olfactory receptor.Sensilla campullacea are the smell, taste or temperature and humidity sensors.2. Purge and Trap method was the first time for the volatiles collection. Volatiles from living to felled plants were collected by Purge and Trap method, and Headspace Absorption method, and were identified by GC/MS. It proved to be a scientific and reliable way for the analysis of the plant volatiles.3.Based on the first analysis and comparison of volatiles from trunks, branches, and leaves of Platycladus orientalis under their different physiological status (healthy, debilitating and bait wood), The experiment results showed that the volatiles of P. orientalis consist of 17compounds,which are mainly classified into terpene compounds. In three physiological states,α-Pinene, andβ-Phellandrene, 3-Carene are detected in different parts of P. orientalis,and their relative content are higher. Myrcene andα-Phellandrene were detected, butβ-Pinene was not detected from the feeble trees, Bornene, 2-Careen, and Cymene were detection in baited wood.4. Electroantennograms (EAG) activities of S. bifasciatus to host volatile compounds were recorded. The result showed that there were no differences between EAG reaction of the antennas of female and male S.bifasciatus.Limonene and Terpinolene elicited the largest EAG values.EAG responses of the most volatiles from low to high concentration to S.bifasciatus showed an upward trend. These volatiles such as the mixtures ofα-Pinene,Caryophyllene,α-Terpinene,and Limonene;Tthe mixtures of -Carene,α-Pinene,α-Cedrene;the mixture ofγ-Terpinene,α-Pinene,Caryophyllene, and Limonene; the mixtures ofγ-Terpinene,α-pinene, andα-Cedrene; The mixtures ofα-pinene,Caryophyllene, andα-Terpinene when these volatiles were mixed each other with the concentration 1/10 and the ratio of volume 1:1.5. The behavioral response of S. bifasciatus to plant volatiles was tested in a self-made"Y"olfactometer. It was found that different substances and concentration of volatiles influenced behavior reaction to S. bifasciatus. 3-Carene Caryophyllene were the most attractive compounds. 3 - Carene,α-Terpene, and Caryophyllene were attractive to S. bifasciatus, and with the increase of concentration, the attractiveness has been gradually strengthened. The mixture from Terpinolene,γ-Terpinene, 3-Carene,α-Pinene,α-Cedrene, and Caryophyllene was the most attractive to S.bifasciatus in the olfactometer when these volatiles were mixed each other with the concentration 1/10 and the ratio of volume 1:1. The selective coefficient was 0.5947.6. Behavioral response of S.bifasciatus to volatiles was determined by using kinds of traps in field. Terpinolenne,α-pinene and Caryophyllene were more attractive to S.bifasciatus.Some volatile mixtures with the concentration 1/10 and the ratio of volume 1:1, such as the mixture of Terpinolene,α-Pinene,Caryophyllene,Limonene,and mixture of Terpinolene,γ-Terpinene, 3-Carene,α-Pinene,α-Cedrene,and Caryophyllene.7. Through the research of lure technology to S.bifasciatus, It shows that intercept trap and infundibular trap, Releasing rate of plant volatiles could be controlled freely by using mocrocentrifuge dispensers with cotton wicks, were confirmed as the perfect trap that could meet the needs of field test. The effective lured duration of volatile compounds of P.orientalis was only 7-14 days in the forest Therefore the lured volatiles should be replaced and made up timely to achieve the desired lured effect.