Aphids on the mustard plants are controlled with the help of .................

Explanation

**Step-by-Step Solution:**

1. **Understanding the Problem**: The question asks how aphids, which are pests on mustard plants, can be controlled. Aphids are small sap-sucking insects that can cause significant damage to crops.

2. **Exploring Control Methods**: Traditionally, farmers have used chemical pesticides to manage pest populations. However, this approach can lead to environmental issues and the development of resistance in pests.

3. **Introduction to Biological Control**: In response to the drawbacks of chemical pesticides, there is a shift towards biological control methods. This involves using natural predators or other biological means to manage pest populations.

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