Long-Term Persistence of the Nuclear Polyhedrosis Virus of the Douglas-Fir Tussock Moth,
Orgyia pseudotsugata
(Lepidoptera: Lymantriidae), in Forest Soil

AbstractFollowing aerial application of a Douglas-fir tussock moth, Orgyia pseudotsugata (McDunnough), nuclear polyhedrosis virus (NPV) product called Virtuss on four plots in 1982, observations were made to determine the impact of these treatments in 1983 and 1984. Treated plots as well as buffer zones between and adjoining the treated plots, and three of the four check plots established in 1982, were monitored. The NPV appeared to have spread from the treated plots to adjoining areas in 1982, effectively reducing the Douglas-fir tussock moth population. This observation suggests that a strategy of spraying alternate swaths of Douglas-fir tussock moth infested stands with this viral insecticide may effectively initiate an epizootic that would control the population at a reduced cost.A naturally occurring NPV epizootic decimated the Douglas-fir tussock moth population in the three check plots in 1983, but severe tree mortality occurred in two of these plots with 60 and 62% of sample trees dead in 1984. Light tree mortality was noted in 1984 in two of the four treated plots with 4 and 7% of sample trees killed. It is concluded that the virus treatments in 1982 were successful in preventing tree mortality.

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PEST MANAGEMENT OF DOUGLAS-FIR TUSSOCK MOTH (LEPIDOPTERA: LYMANTRIIDAE): PREVENTION OF AN OUTBREAK THROUGH EARLY TREATMENT WITH A NUCLEAR POLYHEDROSIS VIRUS BY GROUND AND AERIAL APPLICATIONS

The Canadian Entomologist ◽

10.4039/ent1161533-11 ◽

1984 ◽

Vol 116 (11) ◽

pp. 1533-1542 ◽

Cited By ~ 27

Author(s):

R. F. Shepherd ◽

I. S. Otvos ◽

R. J. Chorney ◽

J. C. Cunningham

Keyword(s):

Nuclear Polyhedrosis Virus ◽

Early Stage ◽

Control Agent ◽

Douglas Fir ◽

Tussock Moth ◽

Orgyia Pseudotsugata ◽

South Central ◽

Polyhedrosis Virus ◽

Nuclear Polyhedrosis ◽

Microscopic Diagnosis

AbstractTwo different application methods were tested using a nuclear polyhedrosis virus as a control agent at an early stage in the outbreak cycle of Douglas-fir tussock moth, Orgyia pseudotsugata (McDunnough), in south central British Columbia in 1981. The virus, which often leads to the development of an epizootic late in the outbreak cycle, was propagated in whitemarked tussock moth, Orgyia leucostigma (J. E. Smith). A helicopter fitted with a boom and nozzle was used for treating four plots (total area 19.8 ha) at a dosage of 2.2 × 1011 polyhedral inclusion bodies (PIB) in an emitted volume of 11.3 L ha−1. Five to eight weeks after spraying, microscopic examination of live larvae showed that 77 to 100% were infected. In ground-spray applications of two other plots, a modified orchard-type sprayer was used to apply 2.4 × 1010 PIB in a volume of 4.5 L per tree. Microscopic diagnosis of live larvae at 8 weeks post-spray revealed 83 and 85% infection.In autumn 1981, no egg masses could be found in the plots treated earlier that year and no larvae were found on the sample trees in 1982 or 1983. The treatment was effective over a range of initial mean larval densities of 41 to 206 m−2 of foliage. At the same time, populations in nearby untreated areas increased in 1982. Little foliage protection was obtained the year of application due to the lengthy virus incubation period, but the trees recovered quickly when populations disappeared due to the virus epizootic.

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AERIAL APPLICATION OF NUCLEAR POLYHEDROSIS VIRUS AGAINST DOUGLAS-FIR TUSSOCK MOTH, ORGYIA PSEUDOTSUGATA (McDUNNOUGH) (LEPIDOPTERA: LYMANTRIIDAE): I. IMPACT IN THE YEAR OF APPLICATION

The Canadian Entomologist ◽

10.4039/ent119697-7 ◽

1987 ◽

Vol 119 (7-8) ◽

pp. 697-706 ◽

Cited By ~ 22

Author(s):

I.S. Otvos ◽

J.C. Cunningham ◽

L.M. Friskie

Keyword(s):

Nuclear Polyhedrosis Virus ◽

Mass Density ◽

Adult Emergence ◽

Douglas Fir ◽

Egg Mass ◽

Tussock Moth ◽

Orgyia Pseudotsugata ◽

Population Reduction ◽

Polyhedrosis Virus ◽

Nuclear Polyhedrosis

AbstractFour 10-ha plots located in Kamloops Forest District, British Columbia, containing Douglas-fir trees infested with Douglas-fir tussock moth were aerially sprayed with nuclear polyhedrosis virus (Virtuss) in 1982 when most larvae were in the first instar. A dosage of 2.5 × 1011 polyhedral inclusion bodies (PIB) per hectare was applied in an emulsifiable oil tank mix to one plot and the same dosage in an aqueous tank mix containing molasses was applied to a second plot. The remaining two plots were treated with dosages of 8.3 × 1010 and 1.6 × 1010 PIB per hectare, respectively, in the oil mix. The treatments were applied with a fixed-wing aircraft fitted with boom and nozzle equipment and calibrated to deliver 9.4 L/ha. A further four plots were selected as checks.Population reduction at 6 weeks post-spray (calculated using a modified Abbott’s formula) was 65% in the plot receiving the lowest dosage and from 87 to 95% in the remaining three plots. Incidence of virus infection, determined microscopically, peaked at 5–6 weeks post-spray with 85–100% of the larvae scored as positive. Levels of naturally occurring virus remained low in the check plots. Adult emergence from the pupae collected in the treated plots ranged from 4 to 19% and from 28 to 43% in the check plots. Reduction in egg-mass density attributed to the treatments was 97% in one plot, 99% in two others, and not determined for the fourth.A virus dosage of 8.3 × 1010 PIB per hectare, which is one-third of the previously recommended dosage, is adequate, and either tank mix is acceptable.

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Replication and serial passage of a multicapsid nuclear polyhedrosis virus of Orgyia pseudotsugata (Lepidoptera: Lymantriidae) in continuous insect cell lines

Canadian Journal of Microbiology ◽

10.1139/m81-178 ◽

1981 ◽

Vol 27 (11) ◽

pp. 1133-1139 ◽

Cited By ~ 7

Author(s):

S. S. Sohi ◽

Jean Percy ◽

J. C. Cunningham ◽

B. M. Arif

Keyword(s):

Cell Lines ◽

Cell Cultures ◽

Nuclear Polyhedrosis Virus ◽

Light And Electron Microscopy ◽

Serial Passage ◽

Continuous Cell Lines ◽

Tussock Moth ◽

Orgyia Pseudotsugata ◽

Polyhedrosis Virus ◽

Nuclear Polyhedrosis

A multicapsid nuclear polyhedrosis virus (MNPV) of the Douglas-fir tussock moth, Orgyia pseudotsugata, propagated in larvae of the white-marked tussock moth, O. leucostigma, was successfully grown in two continuous cell lines developed from minced neonate larvae of O. leucostigma. Polyhedral inclusion bodies (PIBs) appeared in the nuclei of cells within 24 h after inoculation. Cytopathological changes, as revealed by light and electron microscopy, were typical of an MNPV. The virus has been passaged in the cell cultures 55 times. The level of infection during passaging has varied from 15 to 98% of the cells, and the number of PIBs per cell from 10 to 40. The PIBs from the fourth passage of the virus in cell cultures were almost as pathogenic to O. leucostigma larvae as the PIBs produced in larvae.

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