Oviposition inhibitor in umbelliferous medicinal plants for the common yellow swallowtail (Papilio machaon)

Umbelliferous medicinal plants, such as Angelica acutiloba Kitagawa and Angelica dahurica Bentham et Hooker filius ex Franchet et Savatier, account for a large percentage of crude drug consumption in Japan. The most serious problem in the cultivation of umbelliferous medicinal plants is the feeding damage caused by the common yellow swallowtail (Papilio machaon hippocrates C. & R. Felder, 1864). When we compared the numbers of eggs laid by P. machaon on six umbelliferous medicinal plants, the eggs on A. acutiloba, A. dahurica, and Glehnia littoralis Fr. Schmidt ex Miquel were the most numerous, those on Saposhnikovia divaricata Schischkin and Cnidium officinale Makino were rare, and Bupleurum falcatum Linné was not oviposited at all. To identify oviposition inhibitors for P. machaon in B. falcatum, S. divaricata, and C. officinale, the volatile chemical constituents of these umbelliferous medicinal plants were compared with GC–MS. We carried out multivariate analysis of gas chromatographic data and concluded that germacrene d, α-humulene, and trans-caryophyllene play important roles in protecting plants from oviposition by P. machaon. Their oviposition repellent activity was confirmed by the fact that the number of eggs laid on the leaves around a repellent device containing a mixture of germacrene d, α-humulene, and trans-caryophyllene was reduced by 40% compared to a control.