(R)-(+)-limonene, kairomone for Dastarcus helophoroides, a natural enemy of longhorned beetles

1 Chemical cues involved in host location by Dastarcus helophoroides (Fairmaire) (Coleoptera: Bothrideridae), a parasitoid of Anoplophora glabripennis Motschulsky, Monochamus alternatus Hope, Massicus raddei (Blessig), Apriona germari (Hope), Apriona swainsoni (Hope) and Batocera horsfielde (Hope) in the family Cerambycidae, were investigated in a Y-tube olfactometer. Responses of D. helophoroides adults toward odour sources from their host (M. raddei) and host tree (Quercus mongolicus Fisch. ex. Turcz.) were tested in either no-choice or two-way choice tests. Wood with larval tunnels and larvae frass were attractive to D. helophoroides. Both sexes showed attraction to wood with larval tunnels. 2 Volatile chemicals emitted from wood with larval tunnels and larval frass were collected on Porapak Q and analyzed by gas chromatography-mass spectrometry. Several compounds identified from these sources, including alpha-pinene, beta-pinene, Delta-3-carene, limonene and beta-myrcene, were tested against D. helophoroides in the same Y-tube olfactometer. 3 The result showed that D. helophoroides adults were attracted to (R)-(+)-limonene, with or without the background odour from uninfested fresh wood. This may suggest that (R)-(+)-limonene is an important kairomone for this parasitic beetle. 4 Dose-dependent response of D. helophoroides adults to (R)-(+)-limonene indicated that D. helophoroides adults showed significant attraction to (R)-(+)-limonene when release rates exceeded 2.08 mu g/h in Y-tube olfactometer tests. Moreover, significantly more A. glabripennis larvae were parasitized by D. helophoroides in the presence of R-(+)-limonene, relative to the control in cage experiments.