Influence of weather and rearing techniques on mulberry silk worm crops in Kerala
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Date
1998
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Department of Agricultural Entomology, College of Agriculture, Vellayani
Abstract
Investigations were conducted on the effect of weather parameters on the
mulberry silkworm crops reared in different seasons and to evolve suitable rearing
technology for stress seasons in order to improve the rearing during these seasons
and for developing suitable package of practices recommendations for silkworm
rearing in Kerala. The study was conducted during 1992-1996 at College of
Agriculture, Vellayani. The experiments conducted were
Effect of climatic factors on mulberry silkworm crops in different seasons.
Identifying rearing technology for stress seasons of high temperature and
humidity.
Manipulation of feeding schedule with reference to stress seasons and types of
silkworm rearing houses.
To study the effect of climatic conditions on the mulberry silkworm crop,
the silkworms were reared during different identified seasons viz December-
January, February-April, May-July, August-September and October-November in
1993-94. The mulberry silkworms used for the study were bivoltine NB4Dz and
crossbreed PM x NB4D2. Three brushing were done in each season at fortnightly intervals and fifteen continuous rearings were conducted. The important weather parameters recorded were maximum temperature, minimum temperature, maximum humidity and minimum humidity inside and outside the rearing house. The rearing characters like instarwise larval duration, moulting duration, larval
weight, leaf consumption, silk gland weight, disease incidences, missing larval
percentage and economic traits like cocoon weight, shell weight, shell ratio,
effective rearing rate, filament length, reelability and computed parameters like
growth index and growth rate were also recorded. Among the different seasons,
August-September and December-January were identified as the favourable
seasons. October-November, February-April and May-July seasons were found to
be the stress seasons as the biological and economic traits of the different
silkworm races during these seasons were not compromising in comparison with
other seasons. Maximum temperature and minimum temperature show direct
correlations whereas maximum humidity indirectly showed negative correlations
with the economic traits like larval weight, silkgland weight, shell ratio, cocoon
weight and yield.
Second and third experiments were conducted to identify suitable cost
effective and efficient rearing house for these stress seasons and also to evolve
rearing technology so as to reduce cost of production. The treatments for the
second experiment were five different rearing houses along with three different
larval spacings. The rearings were conducted by using the same crossbreed and
bivoltine race used in the first experiment. The rearings were carried out during
1995 and 1996 in the three stress seasons viz May-July, October-November and
February-March.
The observations were recorded in terms of the larval characters and
economic traits of the silkworms NB4D2 and PM x NB4D2 in these seasons. The
results revealed that wider spacing was superior to medium and close spacings in
both races. The rearing houses made of mud brick and thatched roof and burnt
brick and thatched roof were found superior to other rearing houses in all the three
stress seasons during the two year period. Among the different feeding schedules
studied in the third experiment, three feeding a day was mostly on par with four
feeding a day but was advantageous in terms of convenience of feeding time over
other feeding schedules though four feedings recorded higher values for some
biological and economic traits in the different silkworm types during different
seasons. The incorporation of new techniques of rearing the crossbreed silkworm
types in thatched mud wall rearing house, medium spacing of worms and three
feeding a day was found to be an ideal profitable package during unfavourable
seasons as comparable to that of favourable seasons.
Description
PhD
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Citation
171334