Debilitating effects of viral diseases on host Lepidoptera

While viral diseases of Lepidoptera are usually recognized for their ability to kill infected hosts, they may also reduce the fitness of individuals which survive infection. We have surveyed studies in the literature in which qualitative characteristics of individuals following treatment with virus have been evaluated. Most of these studies have involved nuclear polyhedrosis virus (NPV) and cytoplasmic polyhedrosis virus (CPV), but several have used granulosis virus (GV), entomopox virus (EPV), and small RNA viruses. Debilitating effects of viral diseases of Lepidoptera include slower development rates, lower pupal and adult weights, reduced reproductive capacity, and shorter adult longevity. These effects were observed more frequently in studies of CPV- than NPV-treated hosts. We evaluate the potential impact of debilitating effects of viral disease by comparing the net reproductive rate (R(o)) of control and treated samples of the host. Studies using CPV and NPV showed significant reductions in R(o) from debilitating effects as well as from mortality, when compared to R(o) based on mortality alone. Sublethal effects were tested for and confirmed more frequently in studies using CPVs than those using NPVs. Little evidence exists for dose-dependent sublethal effects, but in studies involving NPV later instars tended to show stronger effects. (C) 1996 Academic Press, Inc.