SERICULTURE

Disease

Pebrine
It is the most destructive disease caused by protozoa, Nosema bombyscis. The worms become very dull and they have poor appetite, irregular moulting and the skin becomes wrinkled.

Flacherie
Caused by bacteria, promoted by high temperature, high humidity and ventilation, bad leaf quality, over feeding and low alkalinity of the gut. Digestive and circulatory systems are damaged and the symptoms are loss of appetite and diarrhoea.

Grasserie
Mostly seen in riping larvae. Caused by Borrlina virus. Infection is induced by extreme low and high temperature. Swelling of the inter-segmental region, shining skin, rupture of body wall, oozing of body fluid and endless crawling are symptoms. Such worms do not moult and spin.

Mascardine
The fungi Beauveria bassiana, Spicaria prasina and Isaria farinosa are causal agents. The infected larvae lose appetite. Specks of oozing oily substance without any clear-cut margins appear on the skin. Body generally hardens and becomes stiff.

Prevention and control

1. Disinfect the rearing room and equipment before rearing.
2. Use only disease free layings from authorized agencies.
3. Dip the egg cards in 2% formalin solution for 20 minutes before incubation.
4. Collect undersized larvae and destroy regularly by burning or burrowing in soil.
5. Feed good quality leaves of correct stages.
6. Avoid over feeding and under feeding
7. Clean the bed every day and burn the infested litter.
8. Use RKO powder at every moulting before resumption of feeding.
9. Maintain humidity only to the desired level.

Pests

Uzi-fly (Trycholyga bombycis)
It is a serious parasite of silkworm larvae and pupa causing heavy loss. Adult is a large fly with prominent black and gray stripes. The fly prefers later instars to the earlier ones for oviposition.

Control

Prevent the entry of fly into the rearing room by providing wire mesh or nylon net on doors and ventilators. Burn the pest-affected larvae. Apply chlorpyrifos on the ground and crevices of walls of rearing house. Other pests are ants, lizards, rats, squirrels, dermestid beetles and birds.

Last updated: 26-4-2007