1Forestry and Forest Products Research Institute, 305-8687, Tsukuba, Japan.
2Department of Physical Sciences, University of Oulu, Linnanmaa, 90570 Oulu, Finland.
In response to herbivory, some plants increase the production of volatiles, which are used by carnivores locating the herbivore. In the Japanese red pine, Pinus densiflora, monoterpenes and EtOH are released in an increased concentration two weeks after the infection by the pinewood nematode, Bursaphelenchus xylophilus, the pathogen of the pine wilt disease. The nematodes drop off from the tracheae of its vector, the pine sawyer, Monocahmus alternatus (Coleoptera: Cerambycidae), and enter the wood tissue when the beetles feed on young barks of pines for maturation. It has been confirmed that M. alternatus uses these monoterpens and EtOH to locate the oviposition site and oviposits on these weakened trees infected by nematodes. The larvae of Trogossita japonica (Coleoptera: Trogossitidae), a predator of the pine sawyer, also have been found on the trees infested with M. alternatus, suggesting the possible and preferential oviposition site for female T. japonica. Therefore, electrophysiological and behavioral observations were made in the laboratory on the responses exhibited by T. japonica to monoterpenes, since such positive responses will enhance the chances of encounter with the prey. The predators have shown positive response to alpha-pinene in EAGs as well as olfactometer assays.