Silkworm Disease Diagnosis through Molecular Approach and their Management

Silkworm has a greater biotic potential and the resistance is continuously offered by the environment which includes biotic and abiotic factors thus influencing the cocoon production qualitatively and quantitatively. The abiotic environmental resistance component largely includes the weather factors such as temperature, relative humidity, photoperiod etc., in respect of silkworm and unfavourable weather conditions that lead to poor harvest of mulberry. The abiotic factors usually affect the growth and development of silkworm and predispose the silkworm to the biotic causes i.e., infectious diseases. The biotic factors responsible for low cocoon crop production are the silkworm diseases caused by protozoa, fungi, bacteria and viruses. Extent of crop loss due to fungal disease caused by white muscardine and green muscardine was 5-20 per cent,virus disease caused by grasserie (NPV) was 15-20 per cent, bacterial disease reduces the crop loss upto 10-15 per cent and pebrine gives 5-10 per cent damage, respectively. The history of sericulture reveals devastating impact of microsporidiosis in several sericultural countries resulting in severe damage to sericulture industry. Though, the disease is known from very remote times, it attracted the attention of sericulturists only during the 17th century. The first scientific record of the occurrence of the disease came from European countries in 1809 and the disease wiped off sericulture there. This was followed by another report from France in 1845 where the annual production of cocoons came down from 26,000 tones in 1853 to 4000 tones in 1865 due to epizootics of microsporidiosis and subsequently collapsed the French and Italian silk industry. Later the disease spread to Spain, Syria and Romania (Steinhaus, 1949). In India, the first report of the occurrence of the disease was from Mysore in 1866 followed by an epidemic level outbreak of the disease in Kashmir in 1878 (Baig et al., 1997).