Which of the following organisms is used to get rid of mosquitoes from the fields ?

Options

A. Ladybird
B. Dragonflies
C. Trichoderma species of fungi
D. Bacillus thurigiensis

Answer

To solve the question, we need to identify which organism is commonly used to control mosquito populations in fields. Let's analyze each of the options provided:

1. **Ladybird**: Ladybirds are known for their role in controlling aphids and other pests, but they are not specifically known for controlling mosquito populations.

2. **Dragonflies**: Dragonflies are natural predators of mosquitoes. They feed on both adult mosquitoes and their larvae, making them effective in controlling mosquito populations in aquatic environments.

3. **Trichoderma species of Fungi**: Trichoderma is a genus of fungi that is primarily used for biological control of plant pathogens and is not known for controlling mosquito populations.

4. **Bacillus thuringiensis**: This is a bacterium that produces toxins harmful to certain insects, including mosquito larvae. It is often used in biological control programs to manage mosquito populations.

Now, let's summarize the findings:

- **Ladybird**: Not effective against mosquitoes.
- **Dragonflies**: Effective predators of mosquitoes.
- **Trichoderma**: Not effective against mosquitoes.
- **Bacillus thuringiensis**: Effective against mosquito larvae.

Based on this analysis, the best answer to the question is **Dragonflies**, as they are known to actively prey on mosquitoes.

### Step-by-Step Solution:
1. **Identify the organisms listed**: Ladybird, Dragonflies, Trichoderma species, Bacillus thuringiensis.
2. **Evaluate each organism's role**: Determine if they are known to control mosquito populations.
3. **Analyze the effectiveness**:
- Ladybird: Controls aphids, not mosquitoes.
- Dragonflies: Predators of mosquitoes.
- Trichoderma: Controls plant pathogens, not mosquitoes.
- Bacillus thuringiensis: Targets mosquito larvae.
4. **Select the most effective organism**: Dragonflies are the most effective at controlling adult mosquitoes.