Abstract
Susceptibility of many insects to baculoviruses decreases with host development (Hochberg 1991), whereas the time required for infected hosts to die increases with larval age (Boucias et al. 1980; Bucher and Turnock 1983; Smits and Vlak 1988). The actual mechanism of this phenomenon, however, has not been established in many cases. The present study was undertaken to investigate the effect of larval age on the susceptibility of Spodoptera litura Fabricius to nuclear polyhedrosis virus (NPV) through oral and intrahaemocoelic routes of infection.