Studies on the pathogenicity of microsporidia isolated from insect pests of mulberry and some other agricultural crops to the silkworm, Bombyx Mori L.

Abstract

Microsporidiosis of silkworm is caused by a highly virulent parasiticmicrosporidian, Nosema bombycis. In addition to Nosema bombycis, several other strains and species of microsporidia have been isolated from the infected silkworms from time to time and the disease epizootic has become increasingly complex as more number of strains and species are being identified to be infecting silkworm. Microsporidia not only infect the silkworm, Bombyx mori L., but also different insect pests of mulberry and other agricultural crops. The infected insect pests of mulberry and also the insect pests from nearby agricultural crops that are casual visitors of mulberry gardens liberate the microsporidian spores along with their scales and faecal matter on the mulberry leaf and thereby contaminate the mulberry leaf. As a result, different microsporidia gain entry to silkworm rearing throu contaminated mulberry leaf and cross infect the silkworm. Hence, the present study was undertaken with an aim to investigate the various aspects of microsporidiosis in the silkworm, Bombyx mori L caused by microsporidia released from different insect pests on the mulberry eaves. In the present study, different insect pests of mulberry and other agricultural crops ere collected from mulberry gardens and agricultural crop fields in and around newlineMysore, Karnataka. The collected insects were screened for microsporid ian nfection and microsporidian spores were isolated from infected specimens. These spores were purified and their infectivity to silkworm was confirmed following Koch s postulates. The morphological characterization of the isolated microsporidia was carried out through light microscopy and micrometry and compared with that of the standard strain, Nosema bombycis. Scanning electron microscopic studies were also carried out to study the surface texture of the spores of the isolated microsporidia in comparison to that of the spores of Nosema bombycis.