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Journal of Biological Sciences

Year: 2012 | Volume: 12 | Issue: 1 | Page No.: 1-14
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Authors

Satadal Chakrabarty

B. Manna

A.K. Saha

B.B. Bindroo

Keywords

Research Article

Comparative Study on Effect Different Types of Nosema sp. (Microsporidia: Nosematidae) on Mulberry and Vanya Silkworms

Satadal Chakrabarty, B. Manna, A.K. Saha and B.B. Bindroo
The spore production of Nosema sp. in mulberry silkworm, Bombyx mori and non-mulberry silkworms, tasar, Antheraea mylitta D.; Eri, Philosamia ricini B. and muga, Antheraea assama Ww. were examined and found that spore multiplication in the host followed a logistic pattern of development. Inoculum concentrations of Nosema sp. during various seasons is the most important factor for the development of pebrine disease in mulberry and non-mulberry silkworms. Mean larval mortality in mulberry silkworm was high (90.00%) when larvae inoculated with low concentration (1.52x106 spores mL-1) of N. bombycis and it was low (66.48%) during March-April and gradually decreased during December-January (28.85%) and May-June (25.21%), respectively. The spore multiplication reaches its peak maximally in moth stage (2.67x108 spores mL-1). However, the rate of multiplication of pathogen decreased (2.0x108 and 1.4x108 spores mL-1) with the higher inoculum concentrations of pathogen (1.52x108 and 1.52x107 spores mL-1) respectively. The high larval mortality (85.00%) was recorded in A. mylitta during cross-infection with high dose (1.52x108 spores mL-1) of N. assamensis as compared to same dose of N. bombycis and N. mylitta and mean seasonal mortality was high during August-September (73.95%) followed by October-November (63.55%). Generally, larval mortality in A.mylitta was recorded high (61.44-85.00%) irrespective of variation in pathogen, inoculum concentrations and seasons. Maximum larval mortality was recorded in 3rd instar (39.44%) and 4th instar (20.55%), respectively. Multiplication of N. mylitta in moth stage was high (4.0x109 spores mL-1) in comparison to any stage of larva or pupa, when inoculation was done at 1st instar. Mortality in eri larvae with the infection of N. ricini and cross-infection with N. bombycis, N. mylitta, N. assamensis were not observed even after 3rd successive inoculation with high doses (1.52x108 spores mL-1) of above pathogens. Mortality percentage was found always high (52.00-100%) in muga larvae infected by N. bombycis, N. mylitta, N. ricini and N. assamensis during August-September in comparison to October-November.
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