# Three Different Biopesticides Against Megalurothrips usitatus (Thysanoptera: Thripidae) and Their Toxicological and Biochemical Impacts

## TL;DR

This study tests three eco-friendly biopesticides for controlling bean thrips, a pest of alfalfa, and finds them effective and sustainable alternatives to conventional chemicals.

## Contribution

The study introduces and evaluates three new biopesticides for sustainable control of Megalurothrips usitatus.

## Key findings

- Beauveria bassiana showed the highest mortality and fastest action against M. usitatus.
- All three biopesticides altered key enzyme activities in thrips, indicating physiological impacts.
- The biopesticides offer a sustainable alternative to conventional pesticides for thrips management.

## Abstract

The bean thrips, Megalurothrips usitatus, is a major pest of alfalfa. Owing to the issues of pesticide resistance and environmental harm associated with conventional chemicals, we evaluated three eco-friendly biopesticides for their control potential. Laboratory bioassays demonstrated that the entomopathogenic fungus Beauveria bassiana, the bacterium Bacillus safensis, and the essential oil from Artemisia ordosica were all effective against M. usitatus. Among them, B. bassiana exhibited the fastest action and highest mortality. Furthermore, these biopesticides induced sublethal physiological effects by modulating the activity of key enzymes involved in detoxification and stress response. Our findings confirm the potential of these natural agents as sustainable alternatives for integrated thrips management.

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 (LT50 = 4.51 days), indicating strong insecticidal activity. The median lethal concentration (LC50) values at 7 days post-treatment were 4.48 × 105 CFU/mL for B. bassiana, 1.67 × 105 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.