What type of control agent is commonly used in biological strategies against termites?

Bacillus thuringiensis (B.t.) is a type of bacterium that is widely recognized as a biological control agent, particularly in the management of pest species like termites. This bacterium produces proteins that are toxic to certain insects when ingested. When termites consume plant material or processed food containing B.t., the insecticidal proteins disrupt their gut function, ultimately leading to their death. This mode of action is specific to certain pests, making B.t. a more environmentally friendly alternative to chemical pesticides, which may affect a broader range of non-target organisms.

Biological control strategies emphasize the use of natural organisms to control pest populations, thereby reducing reliance on synthetic chemicals. Other options listed, such as pyrethrins, piperonyl butoxide, and chlorpyrifos, are all synthetic or naturally-derived insecticides. They work through different modes of action, primarily targeting the nervous system of insects, but they do not fall under the category of biological control agents like B.t. Thus, B.t.'s specific application and effectiveness against termites in biological pest management strategies make it the correct choice.