span >Which of the following microbes can be used as insecticide?

All the microbes mentioned can be used as pesticides. Single cell organisms, such as bacteria, fungi and protozoa, and viruses, have been mass produced and formulated for use in a manner similar to insecticides. Eg - Bacillus Thuringiensis.
Several fungi have been studied as potential microbial insecticides. Beauveria bassiana can affect a wide variety of arthropods. Virus can also be used as insecticide. Baculoviruses are a family of naturally-occurring viruses known to infect only insects and some related arthropods. Most are so specific in their action that they infect and kill only one or a few species of Lepidoptera larvae (caterpillars), making them good candidates for management of crop pests with minimal off-target effects.