Dear student,
a) Viruses of the genera nucleopolyhedrovirus and granulovirus shows insecticidal properties. Baculovirus is the virus which infects arthropods.
b) Baculovirus is species specific showing narrow range of insecticidal application and therefore do not harm plants, animals, bird fish etc. It can even control pests like potato bettle, aphids etc. It affects the rate of development of grasshopper and thus keeps in check the amount of food it hampers.
Regards