The key phytochemical cue D(+)-camphor is a promising lure for traps monitoring the new monophagous camphor tree borer Pagiophloeus tsushimanus (Coleoptera: Curculionidae)

Abstract

The landscape plant, Cinnamomum camphora, is a broad-spectrum insect-repelling tree species, mainly due to a diversity of terpenoids, such as D(+)-camphor. Despite its formidable chemical defenses. C. camphora is easily attacked and invaded by a monophagous weevil pest, Pagiophloeus tsushimanus. Deciphering the key olfactory signal components regulating host preference could facilitate the monitoring and control strategies for this insect pest. Herein, two host volatiles, D(+)-camphor and ocimene, can induce GC-EAD/EAG reactions in both male and female adult antennae. Correspondingly, Y-tube olfactometer assays showed that the two compounds were attractive to both male and female adults. In field assays, a self-made trap device baited with 5 mg dose D(+)-camphor captured significantly more P. tsushimanus adults than isopropanol solvent controls without sexual bias. The trunk gluing trap device baited with bait can capture adults, but the number is significantly less than that of the self-made trap device and adults often fall after struggling. The cross baffle trap device never traps adults. Neither ocimene nor isopropanol solvent control could capture adults. When used in combination, ocimene cannot enhance the attraction of D(+)-camphor to both female and male adults. These results indicate that D(+)-camphor is a key active compound of P. tsushimanus adults for the host location. The combination of the host-volatile lure based on D(+)-camphor and the self-made trapping device is promising to monitor and provide an eco-friendly control strategy for this novel pest P. tsushimanus in C. camphora plantations.