# BioControl 3.0: Biological Control Complex for Pest Control—Enhanced Control of Locusta migratoria manilensis via Combined Application of Metarhizium anisopliae var. acridum and Carabus smaragdinus

## TL;DR

A new pest control method combines a fungus and a beetle to effectively and safely manage locusts without harming the environment.

## Contribution

Introduces BioControl 3.0, a predator-vectored delivery system combining a fungus and a beetle for locust control.

## Key findings

- BioControl 3.0 achieved the highest corrected mortality of locusts with additive effects from predation and infection.
- The fungus was safe for beetles and showed negligible virulence toward them.
- Sequential application (BioControl 2.0) had a negative interaction between predation and infection, limiting efficacy.

## Abstract

The migratory locust is a major agricultural pest. While chemical control is common, it poses significant environmental and health risks. This study proposes “BioControl 3.0,” a novel strategy that combines the insect-killing fungus Metarhizium anisopliae with the predatory beetle Carabus smaragdinus. BioControl 3.0, the predator-vectored delivery complex, achieved notable success rate when controling locusts, because the beetle and fungus worked independently and additively. The fungus was also found to be safe for the beetles and can even help promote plant growth in previous studies. This integrated approach provides a more effective, environmentally friendly, and sustainable blueprint for managing locust outbreaks.

Locusta migratoria manilensis (Meyen) is a highly destructive insect pest worldwide. However, excessive reliance on insecticides has resulted in significant environmental pollution. Biocontrol complexes combine two or more BCAs to address the limitations of individual agents. However, biocontrol complex for locust control has been rarely reported. Here, we propose BioControl 3.0, which integrates Metarhizium anisopliae var. acridum (Driver and Milner) and Carabus smaragdinus (Fischer von Waldheim) for locust control. We evaluated this system through a series of laboratory bioassays and semi-field cage experiments, comparing single-agent applications, sequential combinations (BioControl 2.0), and predator-mediated delivery (BioControl 3.0), and quantified locust mortality and interaction effects between predation and infection We found that M. anisopliae caused >85% mortality of locust nymphs at 1 × 108 conidia/mL (LT50 ≈ 6 days) while exhibiting negligible virulence toward C. smaragdinus. BioControl 2.0 (sequential application) increased mortality compared to single agents. However, this approach revealed a significant negative interaction between predation and infection, which limited the total control efficacy. BioControl 3.0 (predator-vectored fungus) achieved the highest corrected mortality, with predation and infection acting independently and additively (no detectable antagonistic interaction). By leveraging a predatory vector, BioControl 3.0 decouples negative interaction and harnesses dual biotic pressures, offering a cost-effective, environmentally benign alternative to conventional locust control. Our findings provide a blueprint for designing integrated predator-pathogen complexes and optimizing deployment strategies for sustainable management of locust outbreaks.