Abstract
Incidence of some diseases of the oriental tussock moth larvae at limited areas in Aichi Prefecture was surveyed. The diseased larvae were classified into four types, i.e. nuclear polyhedrosis, cytoplasmic polyhedrosis, microsporidian disease or a disease caused by virus and microsporidia simultaneously. The cytoplasmic polyhedrosis and the microsporidian disease were found in the larvae of Euproctis subflava BREMER originally. External symptoms of the larvae infected with nuclear or cytoplasmic polyhedrosis virus were similar to some other lepidopterous insects infected with these viruses respectively. Long rod-shaped particles of the nuclear polyhedrosis virus were consistently observed in ultrathin section of the infected tissues. Size of virus particles was approximately 40×400mμ. A few (1 to 4) virus rods were enclosed in a membrane, and observed in and out of the polyhedral crystal. The cytoplasmic polyhedron was hexagonal in shape, which measured 0.5 to 3.0μ. Symptoms of the larvae infected with microsporidian disease were faint movements and retardation of growth or dwarf. The microsporidia was tentatively assigned to the genus Nosema. The spore was elliptical in shape and ranged from 0.7∼0.9×1.3∼1.6μ. It appeared that the nuclear polyhedrosis mainly broke out in the last instar larva, but microsporidian disease occurred in all larval stages except young instar.
