Contact toxicity, antifeedant activity and oviposition preference of osthole against agricultural pests

Osthole, the dominant bioactive constituent in Cnidium monnieri , has been shown to exhibit acute insecticidal activities. However, its detailed toxicity, antifeedant and oviposition preference effects against agricultural pests has not been fully understood, which has greatly hindered its practical applications. This study is designed to investigate the contact toxicity, antifeedant activity and oviposition preference of osthole against three agricultural pests ( T. urticae , M. persicae and B. dorsalis ) to evaluate its potential agricultural applications. Our results showed that Cnidium monnieri (L.) Cusson (CMC) have a high osthole content of 11.4 mg/g. Osthole exhibited a comparable level of acute toxicity against T. urticae to four other coumarins found in CMC. Osthole demonstrated significant insecticidal activity against first instar nymphs and adults of T. urticae and M. persicae in a dose-dependent manner, but not against B. dorsalis adults. Osthole exposure reduced the fecundity and prolonged the developmental time of T. urticae and M. persicae . Leaf choice bioassays revealed potent antifeedant activity in T. urticae . Furthermore, female B. dorsalis showed a distinct preference for laying eggs in mango juice with 0.02 mg/mL osthole at 48 hours, a preference which persisted at 96 hours. These results provide valuable insights into the toxicity, repellent activity, and attractant activity of osthole, thereby contributing to its expanded use in pest control.