The Ecology and Evolution of Insect Baculoviruses

Abstract

Baculoviruses occur widely among Lepidoptera, and in some species of forest and agricultural insects, they cause epizootics in outbreak populations. Here we review recent developments in baculovirus ecology and evolution, in particular focusing on emerging areas of interest and studies relating to field populations. The expanding application of molecular techniques has started to reveal the structure of baculovirus populations and has highlighted how variable these pathogens are both genotypically and phenotypically at all levels from within individual hosts to among host populations. In addition, the detailed molecular knowledge available for baculoviruses has allowed the interpretation of gene functions across physiological and population levels in a way rarely possible in parasite-host systems and showed the diverse mechanisms that these viruses use to exploit their hosts. Analysis of the dynamic interactions between insects and baculoviruses, and their compatibility for laboratory and field experiments, has formed a basis for studies that have made a significant contribution to unraveling disease interactions in insect populations. In particular, manipulative studies on baculoviruses have been instrumental in developing an understanding of disease transmission dynamics. The results so far indicate that baculoviruses have the potential to be an excellent model for investigations of changes in virulence and resistance in fluctuating and stable host populations.

Microbial Control of Black Cutworm (Lepidoptera: Noctuidae) in Turfgrass Using Agrotis ipsilon Multiple Nucleopolyhedrovirus

“…Baculovirus epizootics occur irregularly in Þeld populations of agricultural pests, including various noctuid species (Cory and Myers 2003). Horizontal transmission depends on susceptible larvae encountering and ingesting a discrete patch of viral OBs that resulted from the death of an infected individual (Cory and Myers 2003).…”

“…Horizontal transmission depends on susceptible larvae encountering and ingesting a discrete patch of viral OBs that resulted from the death of an infected individual (Cory and Myers 2003). It depends in part on the relative density of infected to susceptible hosts.…”

“…Susceptibility to baculovirus infection typically decreases with increasing larval age (Cory and Myers 2003), a phenomenon related in part to the greater capacity of later instars to slough off virally infected midgut tissues (Keddie et al 1989, Hoover et al 2000. A one-time AgipMNPV dose that was lethal to Þrst instars resulted in only 46 and 30% mortality of third and Þfth instars in trials.…”

“…Infected larvae rupture in death, contaminating foliage with millions of occlusion bodies (OBs), the infectious form of the virus, that then are ingested by other larvae. OBs, consisting of virions embedded in a protein matrix, are relatively stable in the environment when protected from UV light (Cory and Myers 2003). Formulating OBs with optical or ßuorescent brighteners often enhances their activity (Shapiro 1995, Dougherty et al 1996.…”

“…Formulating OBs with optical or ßuorescent brighteners often enhances their activity (Shapiro 1995, Dougherty et al 1996. Baculoviruses therefore have potential to provide long-term suppression once introduced among a pest population (Moscardi 1999, Cory andMyers 2003).…”