Effect of larval maturation on mortality induced by nuclear polyhedrosis and granulosis virus infections of Heliothis armigera

All the instars of Heliothis armigera larvae were found to be susceptible to both nuclear polyhedrosis virus (NPV) and granulosis virus (GV). An inverse relationship between mortality and larval age was found in the case of the NPV, while the GV displayed a rather erratic mortality pattern. A degree of maturation immunity against the NPV was found to exist, but the same is not true for the GV. The important role that pupation plays on the effect of a lethal infection is also discussed.