Insecticidal and bacteriostatic activities of extracts from three species of Ligularia

Ligularia virgaurea, Ligularia sagitta and Ligularia rumicifolia are typical dominant populations of poisonous plants in degraded eastern alpine meadow of Qinghai-Tibet plateau. This paper explores utility value from the perspective of “turning harm into benefit”. The Biological activity of extracts from these three plants were investigated by testing and comparing the activities against Mythimna separate, the effects on mycelial growth of Fusarium oxysporum. The results showed that extracts all had strong stomach toxicity activity, contact toxicity and antifeedant activity, and the order was L. rumicifolia > L. virgaurea > L. sagitta. The corrected mortality for stomach and contact were more than 70% and 50% respectively when the concentration of extract from L. rumicifolia was low (5 mg·mL⁻¹); meanwhile, the corrected mortality for stomach and contact could reached 70% and 50% when the concentration of extract from L. virgaurea was 10 mg·mL⁻¹; the corrected mortality for stomach and contact were still less than 50% when the concentration of extract from L. sagitta increased to 20 mg·mL⁻¹. The antifeedant rates were all above 60% when the concentration of extracts from three species of Ligularia were over 2.5 mg·mL⁻¹. The extracts from L. rumicifolia and L. virgaurea had stronger toxicity with LC₅₀ value of 1.067 and 1.851 mg·mL⁻¹, the LC₅₀ of extract from L. sagitta was 27.957 mg·mL⁻¹. The extracts from L. virgaurea, L. sagitta and L. rumicifolia all had significant inhibitory activity on mycelial growth of Fusarium oxysporum (P < 0.01). These results demonstrate that L. virgaurea, L. sagitta and L. rumicifolia have great potential and application prospects for developing as biological pesticide. The results from this paper also provide a new way for the comprehensive control of poisonous plants in degraded meadow.