Question

Viruses of genus Nucleopolyhedrovirus are employed as
A. Gobar gas producers
B. Biological control agents
C. Anaerobic sludge digesters
D. Antibiotics
E. Atmospheric nitrogen fixing agents

Answer 1

Hint:- Nucleopolyhedrovirus (NPV) belongs to the taxonomic group of baculoviruses. These viruses are a class of large, double-stranded DNA viruses. They are host specific and infect only invertebrate hosts. They are commonly known to cause viral disease in caterpillars of pests which infest standing crops.

Complete step-by-step solution:- NPVs are obligate parasites and need a host to reproduce. When they infect a host they invade the cells of the host's body and multiply to form multiple copies. They act as a poison that affects the digestive system of the host. NPV particles called polyhedral inclusion bodies (PIB) successfully infect the pest caterpillar only when it is ingested by the larvae. After ingestion, the virus infects the gut cells. They quickly spread to almost all the tissues in the body through the blood in 24 hours. It takes a few days for NPV to produce an effect in the insect body. The infected insect climbs the tip of a shoot to die and hangs upside down. Its body becomes flaccid and ruptures to release millions of NPV particles on the foliage. This foliage when eaten by other larvae initiates a cycle of infection.
NPV usage in crop fields is highly safe and environment friendly. It is a preferred biological control agent against arthropod pests because of its host specificity, excellent control effects and low levels of resistance response. It does not affect beneficial insects in croplands.
So, the correct answer is (B), Biological control agents.

Note:- Effect of NPV varies on different age groups of insects. A young larva may die within 4 days of ingestion whereas, an older larva may take 5 to 7 days to be killed. This depends on dose and temperature. A high dose or high temperature will accelerate the rate of infection and death. In cold temperatures the infection time is delayed and NPV may take more than 10 days to kill its host.