Impacts of Diseases on the Qualitative Characters of Tropical Tasar Silkworm

Silk is the most beautiful gift of nature which is generally produced by phytophagous Lepidopteran insects commonly known as sericigenous insects and production of the fibre is known as “Queen of Textiles”. The scientific practices of cultivation as well as protection of food plants and rearing of the silkworm altogether constitute a branch of science termed as sericultur. Sericulture is an integral part of our rural economy in an agrarian country like India. It has tremendous potential in improving the economic status of rural people particularly tribal in India. All out efforts are being made to bring about silk revolution in the country to meet the demand of silk goods to the needs of the ever changing fashion technology in the world. As a matter of fact the silk world is constituted of mulberry, non-mulberry and other animal products. Which are known as Mulberry, Tasar, Muga, Eri, Anaphe, Mussel, Spider and Coansilk. It is interesting that the climatic and environmental condition of India make their home land of various silk producing insects and food plants. However, India enjoys the unique distinction being the only country in the world which produces all the important four varieties of natural silks namely mulberry, tasar, eri and muga under domesticated and wild condition on the foliages of host plants during the seed crop and commercial crop seasons. A distinct belt of humid and dense tropical forest sprawling over the central plateau is the home of tasar. It covers the principal states of Jharkhand, Bihar, M.P., Orissa, Chattisgarh, West Bengal, Assam, fingers of Andhra Pradesh and Karnataka.The famous tasar producing species such as Antheraeamylitta, Antheraeapernyi, Antheraearoylei, Antheraeafrithi and Antheraeaproylei. Indian tasar silkworm, Antheraea mylitta D; which is of great commercial interest suffers great loss of crop (70 to 80%) due to diseases like sporozoasis, bacteriosis, virosis and mycosis. The estimated crop loss due to Sporozoasis alone in case of Antheraea mylitta is reported to be in the tune of 40% (Sen and Jolly, 1972). The adverse effect of different diseases on the technological characters of different cocoons of tasar silkworm have been studied (Sen et al. 1973; Choudhary etal. 1974; Sharan and Sharma, 1989). The investigations in relation to the relative effect of different pathogens causing different diseases in sericigenous insects have been carried out (Griyeghey et al., 1974; Jolly 1974; Ahsan, 1975; Akai, Hiromu 1998; Akai, 2005;Arora, S. 2006;Bhattachrya, 2005;Bhatia, 2010;Chakravorty, 2007; Chaudhury, M. 2008; Dikshit, 2007; Pandey, 1989;Pandey, 2012; Prasad, 2011;Mandar et al., 1990Qadri, 2010). The present communication is designed to evaluate the relative effect of four different diseases on the qualitative characters of

The infected cocoons of Antheraea mylitta due to diseases like sporozoasis, bacteriosis, virosis and mycosis were collected during seed crop (July—August) and commercial crop (Sep -Oct.) seasons. The cocoons were stored separately under normal laboratory condition and further analysed for the different qualitative parameters viz. Cocoon wt (gm), Shell wt. (gm), tasar filament length (mtr.), non-breakable filament length (mtr.), filament denier and reelability percentage as per the methods suggested by Jolly (1973). The experiments were carried out for both the seed crop and commercial crop season. A relative picture in relations to four different diseases in respect of qualitative characters of tasar cocoons has been presented in Table-1.

C.D. at 5% level for characters

Table reveals that the qualitative characters of cocoons during seed crop and commercial crop viz, average wt. of cocoons (10.1 and 10.5) due to Sporozoasis (10.7 and 10.9) due to bacteriosis (10.9 and 11.0) due to Virosis (11.2 and 11.8) due to mycosis present evident variations during seed crop and commercial crop as compared to control (12.6 and 12.8). Similarly other qualitative characters such as average shell wt., average length of filament, average non-breakable filament length, average filament denier and reelability during seed crop (0.98, 520, 232, 5.62, 35.3) and commercial crop (1.0, 582, 234, 5.68, 39.5) due to Sporozoasis, (1.20, 560,232,6.12, 38.2) and (1.30, 602, 238, 6.14, 40.3) due to bacteriosis, (1.30, 580, 234, 6.62, 38.9 and (1.40, 610, 240, 6.72, 40.8) due to Virosis and (1.40, 590, 242, 6.62, 40.1) and (1.60, 688, 248, 6.73, 41.2) due to mycosis as compared to control (1.60, 688, 247,6.71, 43.9) and (1.80, 690, 251, 6.79, 44.2) for both the seasons. However, the pathogens also account for the variations. Although, the adverse effect of Sporozoasis as compared to three other diseases on the qualitative characters of tasar cocoons is highly significant. The table further reveals that the adverse effect of mycosis on quality of cocoons is relatively less than sporozoasis, virosis and bacteriosis. The qualitative characters of cocoons during commercial crop season have been found to be relatively better than the seed crop season, thus account for the seasonal variation. The aforesaid results have led us to believe that the relative variations in the qualitative characters of cocoons in respect of four different diseases are probably due to different nature and mode of infection of four different pathogens. However, Sporozoasis appear to be more serious than the three other pathogens such as bacterial, viral and fungal. The relative superiority of commercial crop cocoons as compared to seed crops cocoons in respect of diseases is presumed due to the differences in the environmental conditions between the two different seasons. Thus it is logical to believe that commercial

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