Abstract
Changes in the resistance to the infection with NPV was investigated by subjecting 4th an 5th instar larvae to low temperature (5 and 10°C) and high temperature (33, 35 and 37°C) treatments for various periods of time immediately after ecdysis. Although the resistance of the 5th instar larvae to NPV was not reduced by treatments at 10 and 33°C for 24 hours, the larvae became markedly susceptible to NPV after treatments at 5, 7 and 37°C for 24 hours. The resistance of the 4th instar larvae to NPV ws reduced, when the low temperature (5°C) treatment was applied for 3 hours, whereas the resistance of the 5th instar larvae was reduced, when they were subjected to the treatment for 6 hours. The resistance of the 4th instar larvae to NPV was not reduced when they were subjected to the high temperature (37°C) treatment for 6 hours, whereas the resistance of the 5th instar larvae was reduced when they were exposed to the treatment for 3 hours.
