Pathogenicity of pebrine disease, Nosema bombysis on mulberry silkworm.

摘要

The pathogenicity of N. bombysis (at 1 x x 105, 1 x x 107 and 1 x x 109 spores/ml) was investigated on two silkworm (Bombyx mori) hybrids, i.e. SH6 x NB4D2 and NB4D2 x KA. All the infected batches of silkworm behaved as normal worms and did not exhibit any conspicuous symptom of pebrine disease in the 1st and 2nd instar larvae. The first causality on larvae was recorded on the 9th day post inoculum of the pathogen. In general, 10-14% mean mortality was recorded in the 3rd instar, while 19-30% mortality in the 4th instar of the silkworm larvae in all the treated batches of the two silkworm hybrids. The maximum mortality (45.6%) of silkworm larvae was recorded in the 5th instar larval stage of all the treated batches. SH6 x NB4D2 showed maximum mortality (62.0+or-1.15) of the 5th instar larvae at 1 x x 109 spores/ml, followed by 1 x 107 spores/ml (60.0+or-1.15) and 1 x 105 spores/ml (45.0+-1.52). NB4D2 x KA showed maximum mortality (59.0+or-1.25) of the 5th instar larvae at 1 x 107 spores/ml, followed by 1 x x 109 spores/ml (58.0+or-1.57) and 1 x x 105 spores/ml (44.0+or-0.57).