🦠 Silkworms Pests

👉🏻 Diseases of Mulberry Silkworm can be classified based on casual organism type:

1. Protozoan Disease (Pebrine)
2. Viral Disease (Grasserie)
3. Bacterial Diseases (Flacherie)
4. Fungal Diseases (Muscardine)

Pebrine (Protozoan Disease)

• Pebrine Disease of silkworm is caused by protozoan, Nosema bombycis.
• It is a major disease of Munga Silkworms.
• Mother moth examination is done to check Pebrine disease.
• Diseases larvae show slow growth, undersized body and poor appetite.
• Diseases larvae reveal pale and flaccid body. Tiny black spots appear on larval integument.
• Pebrine is also called pepper or corpuscle disease because of black pepper like spots that occur in the body of silkworm.
• Dead larvae remain rubbery and do not undergo putrefaction shortly after death.

  

Grasserie (Viral Disease)

• Causative agent: Bombyx mori Nuclear Polyhedrosis Virus.
• The skin of worms becomes shiny before moulting and fails to moult.
• The infected worms move restlessly along the rim of the trays.
• The inter segmental swelling appears and the color of the body becomes yellowish.
• Bamboo cane like appearance of silkworm is the symptom of Grasserie (Jaundice) caused by Borrelina virus.
• A destructive viral polyhedral disease of silkworm that is related to wilt and is marked by spotty yellowing of the skin and internal liquefaction also called jaundice in silkworm.

Flacherie (Bacterial Disease)

• Causal organism: Streptococci, or Bacillus bacteria.
• Bacteria and sometimes in combination with viruses cause the disease individually or in combination.
• Fluctuating temperature and humidity and poor quality mulberry predispose the disease development.
• The infected worms show loss of appetite.
• Head and thorax become translucent.
• Growth and development of the worms become irregular due to shrinkage of the body.
• Retarded growth, empty foregut and midgut.
• It is a major disease of silk worm.
• Flaccidity of larvae is major symptom.
• The larvae vomit gut juice, develop dysentery and diarrhea which includes excretion of chain type feacus.

Muscardine (Fungal Diseases)

• White Muscadine is caused by a fungus Beauveria bassiana
• Green Muscadine is caused by a fungus Metarrhizium anisopliae
• Aspergillosis is common in young age silkworms and the infected larvae will be lustrous and die.
• Dark green (Aspergillus flavus) or rusty brown (Aspergillus tamari) mycelial cluster are seen on the dead body.
• The diseases larvae prior to death will be lethargic and on death are flaccid.
• Oil specks may be seen on the surface of larvae.
• They gradually be fome hard, dry and mummify into a white or green coloured structure.
• The diseases pupae will be hard, lighter and mummifies.

Uzi Fly

• Exorista sorbillians
• 4th and 5th instar of silkworms are infested by Uzi fly.
• Presence of black spot or scar in the body of silkworm or holes in coccon is due to the infestation of Uzi fly.
• Occurrence & Symptom:
  • The uzi fly, Exorista bombycis is a serious endo-larval parasitoid of the silkworm, Bombyx mori, inflicting 10-15% damage to the silkworm cocoon crop in the premier silk producing states of Karnataka, Andhra Pradesh and Tamil Nadu
  • Uzi fly occurs throughout the year, but severe during rainy season. Presences of eggs or black scar on the silkworm body and maggot emergence hole at the tip of the cocoon are the typical symptoms of uzi fly attack.
  • As soon as the uzi fly enters into rearing house, it lays one or two eggs on each silkworm larva. After 2-3 days, egg hatches, enters inside the larva and feed on internal contents for 5-7 days, after which it comes out by rupturing the larva. The maggot pupates in a dark corner or cracks & crevices in about 18-24 hours. The pupal stage lasts for 10-12 days. If the uzi fly infests at last instar, the uzi maggots come out after cocoon formation by making a circular hole.

Dermistid beetle

• Dermistid beetle (Dermestes cadeverinus) eat the coccons, enclosed pupae and eggs of silkworms.
• Occurrence & Symptom:
  • Dermestid beetles, Dermestis ater are known to attack pierced cocoons in cocoon storage rooms.
  • The female beetles lay about 150-250 eggs in the floss of cocoons.
  • The beetles migrate from cocoon storage room to grainage and attack green cocoons as well as moths also.
  • Generally they attack the abdominal region of the moth.
  • The damage is estimated to be 16.62% on cocoons and 3.57% on moths.

- https://csb.gov.in/
- https://agritech.tnau.ac.in/
- Wikipedia
- https://sericulture.assam.gov.in/
- https://agritech.tnau.ac.in
- Central Sericulture Research & Training Institute, Mysore, Karnataka
- Package of Practices of Mulberry Sericulture for Eastern and North Eastern Region, Central Sericultural Research & Training Institute, Berhampore, West Bengal