Preliminary Studies On Chemical Information Communication Mechanism Between Monochamus Alternatus Hope And Host Plants

Nowadays, controlling insect vector Monochamus alternatus Hope is the main way to control pine wilt disease. In order to improve trap effects, it is important to study the chemical information communication mechanism between M. alternatus and host plants based on chemical ecology. In this paper, the main chemical compounds of volatile oil distilled from different pinus species were identified. EAG responses of adults to host plant volatile oils were tested. Five kinds of components which have high efficiency to attract M. alternatus were selected. The external morphology of antennal sensilla was observed by scanning electron microscopy. The results are summarized as follows:1. Ten kinds of volatile oils were obtained from five pinus species by steam distillation. Their components were analyzed and identified by GC-MS. The results showed that more than 80 components existed in ten volatile oils, and 13 of them were common ones. The major components were monoterpenoid, sesquiterterpenoid, alcoholates, aromatics, etc. The components and relative content changed among different volatile oils.2. The results of electrophysiological assay showed that the receptor organs sensitive to volatile compounds were located on the distal end of antenna. The difference of EAG responses between male and female was not notable.3. The relative values of adults' EAG responses to volatile oils obtained from different host were compared in this paper. The results showed that, as for the 20^th-30^th day female adults, the relative value got from the wilt pine (Pinus massoniana) was higher than that from the healthy ones, and that from the twigs was higher than that from the leaves. But the contrary result occurred when the 3^rd-10^th day adults were tested. The relative value got from the healthy pine was higher than that from the wilt ones. The order of the relative value amone health pines was as follows: P. thunbergii is higher than P. elliottii, but lower than P. massoniana.4. EAG responses of adults to 10 compounds were tested. The results showed that, loaded with 0.04ul stimulus, the adults had the strongest responses to alpha-pinene, beta-pinene, camphene, alpha-terpinene, alpha-terpineol, ethanol, methanol, followed by isolongifolene, and the responses to trans-caryophyllene and cineole were the weakest. The 13th-16th day adults were of the most sensitive EAG responses among three periods tested. The values of EAG activity of compounds mixed with different components are higher than the monomer s. The laying season female adults were more sensitive to the compounds added with ethanol. The values of EAG activity became lower when non-host volatile matter was added. The EAGdose-response of female showed there existed a suitable concentration range in volatile compounds. The mixture of alpha-pinene and ethanol 3, alpha-terpinene with 10"4 and alpha-terpineol with 10^. The attractive ability of compounds would be decreased when cineole was added.6. The external morphology of antennal sensilla was observed by SEM. Six types of sensilla were found. Sensilla chaetica type I was considered to be a mechanoreceptor, type II to be a proprioceptor. Sensilla basiconica (type-1 , II ,111) were considered to be olfactory receptors. S. trichodea might be a sensor of contact chemicals.