What type of insecticide is Bacillus thuringiensis often classified as?

Bacillus thuringiensis, commonly referred to as Bt, is classified as a microbial insecticide because it is a bacterium that produces proteins toxic to certain insects. These proteins are activated in the alkaline environment of the insect gut, where they disrupt the digestive processes of target pests, ultimately leading to their death. This classification emphasizes its biological origins and mode of action compared to other types of insecticides.

Microbial insecticides, such as Bt, play a significant role in integrated pest management (IPM) strategies. They are often regarded favorably due to their specificity—targeting only certain insect species without affecting beneficial insects, animals, or humans. This makes Bacillus thuringiensis a valuable tool in sustainable agriculture.

The other classifications do not apply here. Botanical insecticides are derived from plants and contain active compounds extracted from natural sources, while synthetic insecticides are man-made chemicals designed to kill pests. Contact insecticides refer to those that kill pests upon direct contact, which can include both synthetic and natural products, but Bacillus thuringiensis works through ingestion rather than direct contact. Thus, identifying Bacillus thuringiensis as a microbial insecticide captures its biological nature and its specific mode of action effectively.