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Muscardine: a menace to silkworm in winter

Silkworms are prone to infection by several pathogens like virus, bacteria, fungi etc which needs necessary prophylactic measures to prevent the mortality due to diseases. Muscardine is a silkworm disease caused by a fungus called Beauveria bassiana.

The disease prevails mainly in winter season and often causes massive loss in silkworm resulting in poor cocoon yield.

Hence, monitoring and control are essential to avoid economic loss to silkworm rearers.

Infection takes place mainly through the integument (skin). The spores (conidia) are airborne and germinate on contact with silkworm’s integument.

The hyphae then penetrate into the body cavity, grow by sucking the body fluid, invade the tissues and kill the larvae. Low temperature and high humidity in rearing environment favour the infection by this fungus.

Symptoms

Infected larvae lose appetite, become sluggish and die within three to five days of infection.

The dead larvae initially appear flabby but harden later due to complete intrusion of the fungus. Finally, the fungus grows over the body surface to produce infectious conidia for further spread.

Management

Rearing shed and appliances should be disinfected thoroughly to destroy the fungal spores.

Silkworms should be reared with adequate spacing, proper ventilation and hygienic conditions. Infected larvae must be collected and burnt before the appearance of conidia to avoid further spread.

Manipulation of temperature and humidity in the rearing shed by electric heater and by dusting dry slaked lime powder in the rearing bed are easy methods to prevent the infection.

Application of rearing bed cum silkworm body disinfectants like Vijetha and Vijetha supplement etc at 3-5gram/sq. ft. as per the schedule control the disease effectively.

J.Ravikumar

N.Sakthivel

& R.Balakrishna

Regional Sericultural Research Station, Salem

Research Extension Center, Central Silk Board, Srivilliputtur, Tamil Nadu

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