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β-Asarone is the predominant component of the essential oil of rhizomes of Acorus calamus Linn ( Sweet flag). Although rhizome extracts from this plant have long been used for insect pest control, their cytotoxic effects on insect cells are not well understood. In this study, we evaluated the potency of β-asarone as a natural insecticide by using a Spodoptera frugiperda cell line (Sf9). To assess the cytotoxic effects of β-asarone on Sf9 cells, we observed morphologic changes in treated cells and performed a cell proliferation assay and a DNA fragmentation assay. After 24 and 48 h of treatment with β-asarone, the proliferation of the Sf9 cells was inhibited in a dose-dependent manner, with IC 50 values of 0.558 mg/ml at 24 h and 0.253 mg/ml at 48 h. Morphologic changes in β-asarone-treated cells were typical of apoptosis and included loss of adhesion, cell shrinkage, and small apoptotic bodies. The DNA laddering present in β-asarone-treated SF9 cells and annexin V assay confirmed that this compound can induce apoptosis in insect cells.Together, these findings suggest that apoptosis induction may be one mechanism through which β-asarone inhibits the proliferation of insect cells and thus exerts insecticidal effects. K E Y W O R D S apoptosis, botanical pesticide, cell toxicity, Sf9, β-asarone

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Some parasitoids oviposit in nonhosts. Parasitization of nonhosts potentially wastes gametes, risks the death of offspring, and reduces fitness. Associative learning, a strategy for efficient reproduction, has been observed in various parasitoid species. We conducted two types of experiments to reveal whether larval parasitoid wasps, Cotesia kariyai (Hymenoptera: Braconidae), learn associatively by ovipositing in nonhosts. In dissection experiments, we found wasp eggs in both host [Mythimna separata (Lepidoptera: Noctuidae)] and nonhost [Spodoptera litura (Lepidoptera: Noctuidae)] caterpillars. However, the mean number of eggs in nonhosts was significantly smaller than in hosts. In oviposition experiments, most naive C. kariyai females attacked both hosts and nonhosts. On the other hand, wasps that had previously attacked nonhosts tended to avoid them thereafter. We conclude that C. kariyai females may be able to detect and identify nonhost metabolites and/or cuticular hydrocarbons. Negative associative learning enhances C. kariyai reproductive success when hunting in complex host habitats.

This is an excerpt giving an overview of the Special Issue: Biology and Management of Sap-Sucking Pests [...]

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The woodwasp Urocerus albicornis (Fabricius, 1781) (Hymenoptera: Siricidae) is a forest pest native to North America and occasionally introduced into European countries. One of these invasive woodwasps was collected in a local forest in Nagano Prefecture, Central Japan. The collected individual was an adult female ovipositing on a log from a Japanese larch (Larix kaempferi (Lamb.) Carrière). Although several of these woodwasps have been found on imported logs in Japan, this is the first record of the alien woodwasp in a local forest within Japan and Asia. This finding indicates that a population of this invasive woodwasp may be established in Japanese forests.