Detection Technique For Nosema Bombycis In Commercial Silkworm Seeds

The inspection of silkworm eggs is an important measure to prevent spread of pebrine disease in silkworms. The transovarial transmission ratio of Nosema bombvcis is an important factor, which decides the chances of its detection during inspection. During the present study we investigated the transovarial transmission ratio of Nosema Bombycis spores and its spreading. Fifth instar silkworms were infected with different doses of Nosema bombycis spores at different periods, and the transovarial transmission ratio of Nosema bombycis in two races (Qiufeng and Baiyu) were measured. We also determined the sensitivity of detection with different volumes of egg sample. On the other hand, we investigated the status quo of pebrine spreading in silkworm eggs. The following results were obtained.1. Infection to fifth instar silkworm larvae at different durations did not significantly influence the infection ratio in mother moths, and the difference in dose had notable influence on moth infection rate. The infection rate increased with the increase of the dose, when the dose was increased above the critical limit 100% infection rate was obtained. Both the silkworm races Baiyu and Qiufeng, were equally influenced by the high dose.2 The different infection period during fifth instar had significant influence on transovarial transmission ratio of pebrine. were remarkably effected on of fifth instar silkworm. The earlier the infection, the higher was the infection rate. The influence of transovarial transmission on individual silkworms was very prominent. The transovarial transmission ratios in Baiyu andQiufeng were 28. 5% and 30. 0% respectively, and did not have remarkable diversity. 3 The transovarial transmission ratio of pebrine was observed to have diverse influence on commercial silkworm races in Zhejiang province. In the incidence of pebrine, the Japanese strains were more susceptible than the Chinese strains, and the eggs produced during spring-produced were more susceptible than autumn-produced eggs, and had remarkably difference between different egg production units and years.4. The relativity was less ( r=0.2413) between the mother moth inspection and eggs inspection of pebrine.5. The detection rate in silkworm eggs was very low.