Abstract
Changes in the susceptibility of each instar larva of the silkworm, Bombyx mori, to NPV after cold treatment (5°C, 24hr) were studied under an aseptic condition. Inoculum virus was nuclear polyhedrosis visus filtered through a 0.45μm millipore filter after the dissolution of nuclear polyhedra in aikali. Although newly hatched larvae were not sensitive to cold treatment, susceptibility to NPV after cold treatment increased with larval age from the 2nd to 5th instars. Infective NPV was detected in the hemolymph of the 5th instar larvae at 6hr after the peroral admimstration with nuclear polyhedra following cold treatment. (* Faculty of Textile Science, Kyoto University of Industrial Arts and Textile Fibers, Matsugasaki Kyoto 606; ** Suzhou Sericultural College, Jiangshu, China; *** Faculty of Agriculture, Nagoya University, Nagoya 464)
