Resistance to Viral Infection of Silkworm Larvae Reared on Artificial Diet Given Once During the 1st to 3rd Instars

Abstract

Silkworm larvae were reared on an artificial diet given once during the 1st to 3rd instars and on mulberry leaves subsequently. The rearing of the larvae was carried out 5 times from spring to late autumn in a year. Resistance to viral infection in these larvae was compared with that of larvae which were reared on an artificial diet given twice and which were exposed to a low temperature (5°C for 24 hr) and treated with oral administration of nuclear polyhedrosis virus. When the 5th instar larvae were exposed to a low temperature in each rearing season, the induction of nuclear polyhedrosis was observed in 12.25% of the larvae fed once and twice. When nuclear polyhedra were given orally to the larvae, —log LD50 (polyhedra/larvae) was estimated at 1.7-2.0 and 1.6-1.9 in the larvae fed once and twice, respectively. © 1989, JAPANESE SOCIETY OF APPLIED ENTOMOLOGY AND ZOOLOGY. All rights reserved.