Bioactivity screening of plant ethanol extracts against Plutella xylostella and field evaluation of an optimized botanical combination formulation
Jie Zhang, Xiaoe Wang, Xiaoli Xu., Williamson Gustave, Xiaokai Zhang
Plutella xylostella is a major pest of cruciferous vegetables. The prolonged overuse of chemical insecticides has resulted in increased resistance in P. xylostella populations, highlighting the urgent need for environmentally friendly and effective alternative control strategies. In this study, ethanol extracts from 15 plant species collected from the Qinling Mountains of China were systematically evaluated for their insecticidal, antifeedant, and oviposition-repellent activities against P. xylostella. Laboratory bioassays were conducted using leaf-dipping and leaf-disc methods. Among the tested plants, ethanol extracts of Atropa belladonna and Blumea riparia var. megacephala exhibited the strongest biological activities. A. belladonna extract achieved corrected mortality, antifeedant, and oviposition-repellent rates of 83.11%, 89.46%, and 78.57%, respectively, whereas B. riparia var. megacephala extract produced corrected mortality, antifeedant, and oviposition-repellent rates of 73.53%, 87.45%, and 82.14%, respectively. When combined at a volume ratio of 8:2, the two extracts showed enhanced insecticidal activity, with a median lethal concentration (LC50) of 65.762 mg/mL and a co-toxicity coefficient consistent with an additive effect without antagonism. A stable emulsifiable concentrate formulation was subsequently developed through optimization of the solvent and surfactant system. Field trials demonstrated that the 10% botanical formulation achieved a control efficacy of 58.35% at 7 days after application, comparable to that of emamectin benzoate under the tested conditions. These findings suggest that A. belladonna and B. riparia var. megacephala are promising botanical insecticide resources for further investigation in integrated management strategies against P. xylostella. Additional research is required to establish long-term stability, active constituents, non-target safety, and performance across multiple field environments.