Question

Green Muscardine in silkworm is caused by?

• A. BmNPV
• B. Beauveria bassiana
• C. Nomuraea rileyi
• D. Nosema bombycis

Hint:

To distinguish between the muscardine diseases:
- White Muscardine = Beauveria bassiana
- Green Muscardine = Nomuraea rileyi Metarhizium anisopliae
- Yellow Muscardine = Isaria farinosa

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Muscardine is a group of fungal diseases that affect silkworms.
The diseases are named after the color of the fungal spores that cover the infected larvae after they die.
These fungi infect the host by penetrating the insect cuticle, after which they multiply in the hemolymph and kill the insect.

Step 2: Detailed Explanation:
Let us review the causes of the different silkworm diseases listed in the options:
1. BmNPV (Bombyx mori Nucleopolyhedrovirus):
This virus causes Grasserie (or nuclear polyhedrosis), which is characterized by swollen larval segments and a milky white hemolymph.
2. Beauveria bassiana:
This fungus is the causative agent of White Muscardine (also known as Kalkrog in German or Chuna Rog in Hindi).
It is the most common and destructive muscardine disease in sericulture, leaving the dead larvae dry, chalky, and white.
3. Nomuraea rileyi (now Metarhizium rileyi):
This entomopathogenic fungus is a causative agent of Green Muscardine in various lepidopteran larvae, including silkworms.
Another common green muscardine pathogen is Metarhizium anisopliae.
When a silkworm is infected with this fungus, its body initially becomes stiff.
After death, the fungus grows outwards through the cuticle, producing a dense layer of green conidia that gives the mummified larva a green appearance.
4. Nosema bombycis:
This microsporidian parasite is the causative agent of Pebrine, a disease characterized by black spots on the larval body and high mortality.
Thus, Green Muscardine is caused by Nomuraea rileyi among the options listed.

Step 3: Final Answer:
Green Muscardine in silkworms is caused by the entomopathogenic fungus Nomuraea rileyi.
Thus, the correct choice is (3).