Effect of unsaturated fatty acids around pupal chambers of Monochamus alternatus (Coleoptera: Cerambycidae) and Acanthocinus orientalis (Coleoptera: Cerambycidae) on the number of Bursaphelenchus xylophilus (Nematoda: Parasitaphelenchidae) carried by the beetles

Several chemical compounds, e.g., linoleic and oleic acids, have been reported to be attractive to the pine wood nematode, Bursaphelenchus xylophilus, in previous studies. To examine the effects of fatty acids on the number of nematodes carried by Monochamus alternatus and Acanthocinus orientalis, unsaturated fatty acids (linoleic, oleic and hexadecenoic acids) and saturated fatty acids (palmitic and stearic acids) around the pupal chambers of individual beetles of the two species were analysed using gas chromatography-mass spectrometry. The number of nematodes carried by individual M. alternatus was large, averaging 1628 (range 2 to 27 200), whilst A. orientalis carried no nematodes. There was no difference in the concentration of linoleic acid around the pupal chambers of M. alternatus and A. orientalis, and the concentration of oleic acid around Monochamus chambers was less than that around Acanthocinus chambers. There were no clear significant relationships between the concentration of linoleic or oleic acids around Monochamus pupal chambers and the numbers of nematodes carried by individual Monochamus beetles emerging from the chambers. It was concluded that the concentration of unsaturated fatty acids around pupal chambers in wilt-killed pine trees could not explain the differences in the numbers of nematodes carried by M. alternatus and by A. orientalis, and the differences in the numbers of nematodes carried by individual Monochamus beetles.