Olfactory Selection Preferences of Pagiophloeus tsushimanus (Coleoptera: Curculionidae) Adults Toward Lauraceae Plants

<i>Cinnamomum camphora</i> is a broad-spectrum insect-repelling tree species because of its high content of terpenoids. However, it is curious that <i>Pagiophloeus tsushimanus</i>, a recently recorded wood-boring pest, has widely infested <i>C. camphora</i> plantations across various administrative districts in Shanghai. The larvae, being concealed within the trunk of <i>C. camphora</i> trees, exhibit characteristics such as hidden activity, strong destructiveness, and being difficult to control. While the primary host plant for <i>P. tsushimanus</i> is <i>C. camphora</i>, preliminary observations have shown that the pest can also complete its life cycle on <i>Cinnamomum chekiangensis</i> and <i>Phoebe chekiangensis</i>. To explore the host selection preference of this beetle, the present study aimed to investigate the olfactory selection behavior of <i>P. tsushimanus</i> adults towards <i>C. camphora</i>, <i>C. chekiangensis</i>, and <i>P. chekiangensis</i>. Results from choice and no-choice tests indicated that both male and female adults exhibited a feeding preference for <i>C. camphora</i> twigs, with females showing a preference for laying eggs on camphor tree twigs as well. Volatile compounds unique in camphor trees were significantly higher in relative content than those on the other two plants that were detected. The Y-shaped olfactometer experiments and electroantennography measurements results showed that male and female adults of <i>P. tsushimanus</i> had a positive chemotaxis towards volatiles released by <i>C. camphora</i> and a negative chemotaxis towards volatiles released by <i>C. chekiangensis</i> or <i>P. chekiangensis</i>. Overall, the findings suggest that both male and female adults have a selective preference for volatiles released by the camphor tree, and this provides a theoretical basis for monitoring and controlling the occurrence of this weevil pest.