BIVOLTINE RACE AND

INTRODUCTION
The bivoltine silkworms produce cocoons with high raw silk recovery and bivoltine silk
excels in quality and International standards. Originating from temperate countries these
breeds have been evolved in luxuriant climate and nutrition. If these are to be raised under
variable tropical conditions, one has to provide optimum conditions to realise the full
competence of the breeds/hybrids. Only a small section of farmers has realised the benefits
of bivoltines. Keeping in view of the optimunn rearing temperature requirements for
bivoltines under tropical condition, the cooler months of the year i.e., August-February are
ideally suited in general for bivoltine rearings in South India when temperature is moderate with
less fluctuations. The success of bivoltine crops depends primarily on the following technologies.
1.0. CRITERIA FOR SELECTION OF NARMERS
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On the basis of previous records, farmers who have harvested successful cocoon crops
(bivoltine) only be selected.
Farmers with a separate rearing house are preferred. If there is no'separate rearing
house, a separate roorn provided with windows and ventilation may be considered.
Those who conduct systematic disinfection before and after each crop.
Farmers having own mulberry garden with irrigation facility for raising quality leaf for
young and late age worms
Those capable of applying adequate quantity of manure (FYM) and fertilizer.
Having adequate rearing equipment.
Having knowledge on the use of disinfectants and maintaining hygiene in the rearing
house during rearing.
Having wire mesUnylon net enclosure to check uzi menace.
Possession of a rearing house of at least 3.6m to 4.5m height preferably with false roofing.
2.0. DISINFECTION
To prevent and/or control silkworrn diseases, more attention should be paid to the
disinfection. The most commonly used disinfectants are formalin and bleaching powder.
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Conduct disinfection preferably at room temperature (24-25"C).Th* efficacy decreases
with temperature less than 20"C.
Soon after the completion of each rearing, wash thoroughly the rearing equipment,
rearing house, incubation room,. leaf preservation room and mounting hall with l%
bleaching powder in 0.3Vo slaked lime * 0.27o detergent solution or 3Vo formalin
(Watanabe, 1995).
Sun dry the appliances thoroughly (15-20 hours).
Disinfect the rearing trays by dipping them into ZVo bleaching powder in 0.37o
slaked lime +0.27o detergent solution or 0.37o slaked lime +0.2Vo detergent