The underlying thesis of this paper is that nucleopolyhedroviruses (NPV), like their insect hosts, exist as populations that can be considered in an ecological context. Population dynamics and transport within and from soil are basic to ecology and, in many cases, long-term survival of NPVs. Morphology, growth characteristics, and indirect effects of the host plants generally have short-term effects on these viruses. The host insect is the most critical component of the NPV environment. NPVs are capable of abiotic and biotic transport, even over long distances with the aid of vertical transmission. NPVs have competitive and amensalistic interactions with other biotic agents. Permissive and non-permissive ecosystems are proposed to partially explain observed differences in NPV epizootics. Vertical transmission may play a role in host resistance, which in turn has co-evolved with viral virulence. Insect control with NPVs, as well as risk assessment, is heavily based on ecology; this is particularly the case for the long-term approaches: release as recycling microbial insecticides, introduction-establishment, and environmental manipulation. Their use as short-term microbial insecticides is also environmentally dependent.
Thus, in spite of their relative genetic and morphological simplicity, NPVs function as parasites in complex ecological relationships that must be fully understood in any given crop/insect/NPV system for successful microbial control.
