Contact Toxicity, Antifeedant Activity, and Oviposition Preference of Osthole against Agricultural Pests

SIMPLE SUMMARY: The excessive utilization of chemical pesticides has resulted in the emergence of pesticide resistance, the disturbance of ecosystems, environmental degradation, and health hazards. Botanical pesticides offer a promising alternative to chemical pesticides, as they have minimal impacts on human health and the environment. Osthole, which has shown pesticidal activities, is the primary bioactive compound in Cnidium monnieri (L.) Cusson. In this study, we assessed osthole for its contact toxicity, antifeedant activity, and oviposition preference against three agricultural pests: the Tetranychus urticae, Myzus persicae, and Bactrocera dorsalis, using laboratory bioassays. Osthole exhibited pesticidal effects against the T. urticae and M. persicae, impeding their fecundity and development. Additionally, it demonstrated significant antifeedant activity against the T. urticae and acted as a potent attractant for oviposition by the B. dorsalis. These findings highlight and expand the potential of osthole as a botanical pesticide for the control of these agricultural pests. ABSTRACT: Osthole, the dominant bioactive constituent in the Cnidium monnieri, has shown acute pesticidal activities. However, its detailed toxicity, antifeedant, and oviposition preference effects against agricultural pests have not been fully understood, limiting its practical use. This study aimed to investigate the contact toxicity, antifeedant activity, and oviposition preference of osthole against three agricultural pests (Tetranychus urticae, Myzus persicae, and Bactrocera dorsalis). Our results showed that the Cnidium monnieri (L.) Cusson (CMC) has a high osthole content of 11.4 mg/g. Osthole exhibited a higher level of acute toxicity against the T. urticae to four other coumarins found in CMC. It showed significant pesticidal activity against T. urticae and M. persicae first-instar nymphs and adults in a dose-dependent manner but not against B. dorsalis adults. Osthole exposure reduced the fecundity and prolonged the developmental time of the T. urticae and M. persicae. Leaf choice bioassays revealed potent antifeedant activity in the T. urticae and M. persicae. Furthermore, the female B. dorsalis showed a distinct preference for laying eggs in mango juice with 0.02 mg/mL osthole at 48 h, a preference that persisted at 96 h. These results provide valuable insights into the toxicity, repellent activity, and attractant activity of osthole, thereby providing valuable insights into its potential efficacy in pest control.