The delta endotoxins are released, by which of the following organism that is most effectively used as biological control?

Options

A. polyhedrosis virus
B. Bacillus thuringiensis
C. Both of the above
D. None of the above

Answer

**Step-by-Step Solution:**

1. **Understanding Delta Endotoxins**: Delta endotoxins are a type of toxin that can form pores in the membranes of cells. These toxins are significant in biological control because they target specific organisms, particularly pests.

2. **Identifying the Organism**: The organism known for producing delta endotoxins is *Bacillus thuringiensis*. This bacterium is well-known for its insecticidal properties.

3. **Mechanism of Action**: When insects ingest *Bacillus thuringiensis*, the delta endotoxins (which are in the form of protein crystals) are activated in the insect's gut. The proteolytic enzymes in the insect break down these crystals, leading to the formation of active toxins that damage the gut lining of the insect.

4. **Biological Control Application**: Due to its ability to specifically target and kill harmful insects without affecting other organisms, *Bacillus thuringiensis* is widely used as a biological control agent in agriculture.

5. **Conclusion**: Therefore, the organism that releases delta endotoxins and is effectively used for biological control is *Bacillus thuringiensis*.

**Final Answer**: *Bacillus thuringiensis*

---