Question

Which one of the following diseases is caused by Nosema bombycis in mulberry silkworm?
a) Muscardine
b) Pebrine
c)Grasserie
d)Flacherie

Answer 1

Hint: Mulberry silk is the highest quality type of silk being produced. The other name of the mulberry silk is Bombyx mori. This species feeds only on the mulberry leaves during its life cycle hence, producing the finest quality of the silk.

Complete answer:
Nosema bombycis is a fungus and obligate intracellular parasite which causes pebrine disease in the mulberry silkworm. The silkworm is highly affected by this parasite. The whole life cycle of this worm gets affected due to this disease. The primary symptoms can be seen as the small brown spots on the body of the silkworm. It causes great economic loss. The eggs which are infected by it are of irregular shape and do not attach to a substratum. It may also lead to the death of some eggs too. The larvae affected by this disease usually lack appetite, have less growth rate and vary widely in size. Most of the larvae die during their moulting. If they complete their moulting then instars born are pale and small. They then get covered with the brown spots and the cocoon that they form is usually very lightly spun. These symptoms may not be visible sometimes. The adult’s species which are infected with pebrine mate poorly and produce a smaller number of eggs.

So, the answer is ‘Pebrine’.

Note: Pebrine can cause huge amounts of loss to the silk industry as the silk quality produced by the worm gets degraded and can’t be used for rearing and for making silk products. The offspring obtained from the affected parents also produce low quality silk.