Study On Attractants For Dendroctonus Valens From Pinus Tabulaeformis And Potential Distribution Of The Pest In China

Red turpentine beetle, Dendroctonus valens LeConte, a native species of North America, severely occurred in Shanxi, Shaanxi, Henan and Hebei Provinces in China since 1998. Its main host species is native pine Pinus tabuliformis Carr. This study is to determine the semiochemicals that are effective on host selection of the beetle by analysis of host tree volatiles profile, and predict the potential spread area of the beetles by geography information system based on the history climate data and similarity analysis of the volatiles from potential hosts.The volatiles of Pinus tabulaeformis were collected by headspace absorption method in natural condition and analyzed by thermal desorption combined with GC-MS from May to September in Qinyuan County, Shanxi Province. Twenty five compounds, mainly monoterpines which are the main components of the volatiles, have been identified. Among them, (R)-(+)-α-Pinene, (S)-(-)-β-Pinene, (S)-(+)-3-Carene are the three main compounds which account for above 96% of monoterpines, and a small amount of other monoterpines, (+)-limonene, myrcene, camphene, phellandrene. There is no significant difference of the relative content of the terpine volatiles between the trunk and needles, but there is difference between healthy and damaged trees, and also between different times and at different breast perimeters.The beetle response to the compounds are tested with Electroantennogram(EAG). The male and female showed different responses to the different compounds, but both sexes had strongest response to (S)-(+)-3-Carene. Males reacted strongly to (R)-(+)- α -Pinene, (-)-limonene, (+)-limonene, and females to (-)-limonene, (+)-limonene, and (R)-(+)- α -PineneIn olfactory test, (S)-(-)- β -Pinene, (S)-(+)-3-Carene,(R)-(+)- α -Pinene are the first three strongest compounds. Compare the results with the different compounds ratio with the three monoterpines, (S)-(-)- β -Pinene also the best, the other two show no significant diffenence. Frass of the beetles, both sexes of adults have a little attractive ability to the beeltes, but much lower than the volatiles from host trees.In the field, (S)-(+)-3-Carene is the best attractant than others, no matter sole or mixture compounds. The active period during the day for the adult showing in the trap catches is after noon till sunset, the adults emergence peak for the adults is during late May. Mark-release-recapture statistics shows that wind direction is main factor of the capture range, and the effective distance for the lures in experiment is more than 50 meters.According the analysis of the history record of the climate, the dry season in Spring in 1997 is the really reason for the occurrence of the pest in 1998. The potential distribution predicted according thecondition of that season is north apart from the distribution now. That is good news for the situation now but if there exist the suitable hosts in the potential area and the pest introduced there, there will be more serious than present.