Environmental Persistence of the Nucleopolyhedrosis Virus of the Gypsy Moth, Lymantria dispar123

Abstract

A bioassay technique was used to estimate the concentrations of infectious gypsy moth nucleopolyhedrosis virus (NPV) that occur naturaIly in leaf, bark, litter, and soil samples taken from woodland plots in Connecticut and Pennsylvania. These concentrations were then compared to those in samples taken sequentially after treatment of these plots with NPV. Results indicated that NPV is a natural component of the host's habitat, persisting in high concentrations in soil, litter, and on bark for at least one year after natural epizootics. Activity of NPV in spray deposits on foliage and bark was measurable for only 3-15 days after NPV treatment, whereas activity of NPV liberated from larval cadavers onto bark was measurable in high concentrations through May of the year foIlowing treatment. The application of NPV at the rate of 2.5 x 10 12 polyhedral inclusion bodies (PIB)/ha to an area already containing high concentrations of naturally occurring NPV did not cause an increase in the environmental NPV load. Although the application of NPV at the rate of 5 x 10 12 PIB/ha to plots containing low natural concentrations of NPV resulted in measurable increases in the NPV load in these plots, these increases were not, overaIl' significantly higher than those occurring in a control plot that was not treated with NPV.

Prevalence of baculoviruses in spruce budworm (Lepidoptera: Tortricidae) populations in New Brunswick

“…For example, in the case of the gypsy moth (Lymantria dispar (L.) (Lepidoptera: Lymantriidae)) NPV (LdMNPV), infection can occur when a larva chews its way out of an egg whose surface has been contaminated by the female moth at the time of oviposition or through later environmental contamination (Doane 1975). LdMNPV can also survive in the soil and leaf litter for years, on tree trunks for months, and on foliage for days (Podgwaite et al 1979). Early gypsy moth instars may pick up LdMNPV infections as they cross the forest floor; early gypsy moth instars acquire Entomophaga maimaiga Humber, Shimazu et Soper (Zygomycetes: Entomophthorales) infections in this manner (Weseloh and Andreadis 1992).…”

Using Simple Models to Predict Virus Epizootics in Gypsy Moth Populations

“…First, Podgwaite et al (1979) quantified populations of gypsy moth NPV particles in the field at two different times after an epizootic, just after the epizootic and a year later, both in litter and soil. These data can be used to give an estimate of the decay rate of the pathogen in the following way.…”

“…The estimate that we use is based on inclusion body survival in soil and in litter, whereas within a season inclusion bodies must survive on foliage to be transmitted. Indeed, when gypsy moth NPV is used as an insecticide it breaks down rapidly on foliage; such insecticidal preparations, however, may reduce the survival ability of inclusion bodies by removing them from the host cadaver (Podgwaite et al 1979). In fact, an estimate of the decay rate F on foliage for the closely related Douglas-fir tussock moth Orgyia pseudotsugata is very close to our estimate for gypsy moth (Dwyer 1992).…”

Estimation of nuclear polyhedrosis virus produced in field populations of the European pine sawfly, Neodiprion sertifer (Geoff.) (Hymenoptera: Diprionidae)

“…However, with increased evidence that insect viruses can persist over long periods within the environment and affect successive insect generations (Podgwaite et al 1979), studies on the virus-host relationship are being regarded as investigations involving two separate, changing and interacting populations, the virus population and the host population. Recent studies into the dynamics of nuclear polyhedrosis viruses (NPVs) of winter moth, Operophtera brumata (Wigley 1976), white-marked tussock moth, Orgyia pseudotsugata (Thompson and Scott 1969), and gypsy moth, Lymantria dispar (Podgwaite et al 1979), have established the importance of the size of the virus population to the development of successive epizootics. Unfortunately, few researchers have had the opportunity to quantify the virus population in terms of polyhedral inclusion bodies (PIBs) liberated from the cadavers of larvae which have succumbed to virus disease during a single epizootic.…”