How does microbial biocontrol agents control butterfly caterpillars?

Explanation

### Step-by-Step Solution:

1. **Understanding Biocontrol Agents**:
- Biocontrol agents are natural enemies of insect pests. They include various organisms such as bacteria, viruses, and fungi that can help manage pest populations, particularly those that harm crops.

2. **Example of a Microbial Biocontrol Agent**:
- One well-known microbial biocontrol agent is **Bacillus thuringiensis (Bt)**. This is a spore-forming bacterium that produces insecticidal proteins.

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