Which of the following is a biocontrol agent commonly used to manage pest butterfly caterpillars?

Bacillus thuringiensis

The correct answer is Option- (2) Bacillus thuringiensis.

Bacillus thuringiensis (Bt) is a biocontrol agent widely used to manage pest butterfly caterpillars. It is a bacterium that produces a toxin called Bt toxin, which is specifically toxic to certain insects, including butterfly caterpillars.

When Bt is applied as a biocontrol agent, the caterpillars consume plant material that has been treated with Bt or come into direct contact with Bt formulations. The Bt toxin is ingested by the caterpillars and binds to specific receptors in their digestive system. This binding triggers the release of toxic proteins that disrupt the integrity of the caterpillar's gut lining, leading to paralysis, starvation, and ultimately, death.

One of the advantages of using Bt as a biocontrol agent is its specificity to target specific insect pests while posing minimal harm to beneficial insects, humans, animals, and the environment. Bt formulations can be applied in various ways, such as sprays, dusts, or incorporated into genetically modified crops, to control pest caterpillars effectively.

Therefore, Bacillus thuringiensis (Bt) is a valuable biocontrol agent used to manage pest butterfly caterpillars by utilizing its specific toxicity to these pests while minimizing adverse effects on non-target organisms.