Question

Which of the following is a viral disease of silkworm?
A. Muscardine
B. Pebrine
C. Maggot disease
D. Flacherie

Answer 1

Hint: Viral diseases are the ones that are caused by means of a virus, these diseases affect all types of organisms.
When affecting plants they show mosaic life appearance.
Silkworm is affected by a virus which it acquires by feeding on an infected mulberry leaf.

Complete answer:
Viral diseases are the ones that are caused by a virus.
Viruses are organisms that can only affect the host machinery and work, they are considered to be non-living until outside the organisms, once inside they take over the host machinery to bring about their replication.
Viral diseases are common to both plants and animals.
In the case of the silkworm, a known viral disease is Flacherie.
It is caused when a silkworm consumes affected mulberry leaves.
On infections, the silkworm becomes very weak and ultimately dies.
Flacherie virus is known to be of two types that are infectious and non-infectious but both are said to be lethal to the silkworm.

This disease is caused by the pathogen named Bombyx mori infectious flacherie virus, cypovirus, densovirus, etc.

Hence, the correct option is (D), Flacherie.

Note: In the case of the silkworm, the viral disease is not caused directly by means of viral invasion but by the consumption of a virus-infected leaf by the silkworm, which causes viral invasion and hence the disease. The virus infecting the silkworm is not airborne.