Abstract
The laboratory toxicity and physiological effects of three biopesticides-the entomopathogenic fungus Beauveria bassiana, the biocontrol bacterium Bacillus safensis, and the botanical insecticide Artemisia ordosica essential oil-were evaluated against Megalurothrips usitatus, a major pest of alfalfa. All three biopesticides caused concentration-dependent mortality in M. usitatus. Among them, B. bassiana showed the highest corrected mortality (88.42%) and the shortest median lethal time (LT(50) = 4.51 days), indicating strong insecticidal activity. The median lethal concentration (LC(50)) values at 7 days post-treatment were 4.48 × 10(5) CFU/mL for B. bassiana, 1.67 × 10(5) CFU/mL for B. safensis, and 2.907 mg/L for A. ordosica essential oil. Moreover, exposure to high concentrations of each agent significantly altered the activities of the protective enzyme peroxidase (POD) and the detoxifying enzyme glutathione S-transferase (GST). Our study supports the use of these biopesticides for thrips management and provides a scientific basis for the eco-friendly and sustainable control of alfalfa pests.