One of these protozoans is threat to apiculture and sericulture

Options

A. Eimeria
B. Ceratium
C. Nosema
D. Monocystis

Explanation

To solve the question regarding which protozoan poses a threat to apiculture and sericulture, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Terms:**
- **Apiculture** refers to the practice of keeping and breeding honey bees for the production of honey and other bee products.
- **Sericulture** refers to the cultivation of silkworms for the production of silk.

2. **Identify the Protozoans:**
- The options provided are:
- Emeria
- Serratium
- Nozema monocystis

3. **Research Each Protozoan:**
- **Emeria:** This is a genus of parasitic protozoans that primarily affect birds and does not have a significant impact on bees or silkworms.
- **Serratium:** This is not widely recognized as a protozoan that affects apiculture or sericulture.
- **Nozema monocystis:** This protozoan is known to affect honey bees and silkworms, causing diseases.

4. **Link Nozema to Diseases:**
- Nozema monocystis was discovered by Louis Pasteur in 1865 and is known to cause:
- **Nosema disease** in honey bees, which can lead to significant declines in bee populations.
- **Pebrine** disease in silkworms, which is a chronic disease that can threaten silk production.

5. **Conclusion:**
- Based on the information gathered, Nozema monocystis is indeed a threat to both apiculture and sericulture due to the diseases it causes in honey bees and silkworms.

### Final Answer:
The correct answer is **Nozema monocystis**.

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