Define biocontrol. Which fungus is used for the treatment of plant diseases?

Explanation

**Step-by-Step Text Solution:**

1. **Definition of Biocontrol:**
- Biocontrol, or biological control, refers to the method of controlling pathogenic organisms, such as pests and diseases, using other living organisms. This approach utilizes natural predators or parasites to manage the population of harmful organisms, thereby reducing their impact on crops and plants.

2. **Understanding Pathogenic Organisms:**
- Pathogenic organisms, commonly known as pathogens, are microorganisms that cause diseases in plants and animals. These can include bacteria, fungi, viruses, and nematodes.

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