Quantitative Analysis of a Pathogen-Induced Premature Collapse of a “Leading Edge” Gypsy Moth (Lepidoptera: Lymantriidae) Population in Virginia

1999 ◽  
Vol 34 (1) ◽  
pp. 84-100 ◽  
Author(s):  
R. E. Webb ◽  
G. B. White ◽  
K. W. Thorpe ◽  
S. E. Talley
Keyword(s):  
Gypsy Moth ◽  
Lymantria Dispar ◽  
Nuclear Polyhedrosis Virus ◽  
Leading Edge ◽  
Late Season ◽  
Early Appearance ◽  
Entomophaga Maimaiga ◽  
Resting Spores ◽  
Nuclear Polyhedrosis ◽  
Second Wave

The population dynamics of a “leading edge” (= at the edge of the expanding gypsy moth invasion) gypsy moth, Lymantria dispar (L.), population was monitored for 3 years (1995–97), with emphasis on the interactions of the gypsy moth nuclear polyhedrosis virus (LdNPV) and the fungus Entomophaga maimaiga Humber, Shimazu, & Soper. Gypsy moth populations in the woodlots varied from very sparse to high (potentially defoliating) levels. LdNPV was strongly density dependent, being confirmed only from the higher populated woodlots. In contrast, the fungus was similarly active in both sparse and highly-populated woodlots. In 1995, the fungal epizootic developed late in the season, with most larvae succumbing during stadia 5–6 and producing mainly resting spores (azygospores). Estimated mortality due to fungus averaged 68% in high-density plots and 85% in low-density plots. LdNPV mortality occurred in a two-wave epizootic, although second-wave LdNPV mortality was undoubtedly reduced because of the reduction of late-season larvae due to fungus activity. Estimated mortality due to LdNPV averaged 14% in highly-populated plots and 1% in low-population plots. In 1996, high levels of fungal-induced mortality occurred earlier in the gypsy moth season than in the previous year. Most gypsy moth larvae in 1996 died in a mid-season wave of fungal-induced mortality, with necropsied cadavers containing only conidia. This resulted in relatively few larvae surviving to late instars. At this time, a second wave of fungus-induced mortality occurred, with over half of the necropsied cadavers containing resting spores. The depletion of the gypsy moth populations by the fungus in 1995 resulted in a greatly reduced first wave of LdNPV in all plots in 1996, and perhaps due to the early appearance of the fungus in 1996, LdNPV was nearly absent from late-season larvae collected from all plots. In 1997, gypsy moth populations were uniformly low, and no dead larvae were found in any of the plots.

Hydraulic Spray Application of Gypchek as a Homeowner Control Tactic Against Gypsy Moth (Lepidoptera: Lymantriidae)

1990 ◽  
Vol 25 (3) ◽  
pp. 383-393 ◽  
Author(s):  
R. E. Webb ◽  
J. D. Podgwaite ◽  
M. Shapiro ◽  
K. M. Tatman ◽  
L. W. Douglass
Keyword(s):  
Gypsy Moth ◽  
Lymantria Dispar ◽  
Inclusion Bodies ◽  
Treatment Effects ◽  
Nuclear Polyhedrosis Virus ◽  
Spray Application ◽  
Laboratory Bioassay ◽  
Early Season ◽  
Late Season ◽  
Nuclear Polyhedrosis

Gypsy moth, Lymantria dispar L., nuclear polyhedrosis virus (NPV) was applied by ground equipment at the rate of 2.5 × 1012 polyhedral inclusion bodies (PIB's) per ha to the lower half of ten trees (per plot) in homeowner-sized plots in Hardford and Baltimore Counties, MD, in 1986. A laboratory bioassay of field collected larvae indicated that a highly significant (P < 0.001) increase in early season mortality of gypsy moth larvae due to NPV occurred in the zone of spray, compared to mortality in a similar foliage zone in untreated plots. Late-season treatment effects varied greatly, in apparent response to significant (P < 0.05) area effects.

Effects of Blankophor BBH, a Virus-Enhancing Adjuvant, on Mortality of Gypsy Moth (Lepidoptera: Lymantriidae)

1999 ◽  
Vol 34 (4) ◽  
pp. 391-403 ◽  
Author(s):  
R. E. Webb ◽  
R. A. Peiffer ◽  
R. W. Fuester ◽  
M. A. Valenti ◽  
K. W. Thorpe ◽  
...  
Keyword(s):  
Gypsy Moth ◽  
Lymantria Dispar ◽  
Inclusion Bodies ◽  
Nuclear Polyhedrosis Virus ◽  
Obvious Effect ◽  
Virus Dose ◽  
Polyhedrosis Virus ◽  
Nuclear Polyhedrosis ◽  
Second Wave

We examined aspects of the gypsy moth, Lymantria dispar (L.)/nuclear polyhedrosis virus relationship, and the effects of Blankophor BBH on that relationship, that might impact the timing of virus kill in a cohort of treated larvae. We studied this relationship both for virus and enhancer applied together and separately. We found that a portion of larvae ingesting virus polyhedral inclusion bodies die later (more than 4 wk after infection) in the season, and that this can be affected by the presence of Blankophor BBH if the virus dose is above a certain level (in this study, 107 polyhedral inclusion bodies per 378 liters). Furthermore, the pattern of mortality resulting from virus ingestion was elucidated. This pattern was affected by Blankophor BBH, but only when the virus dose was above a certain higher level (in this study, 1011 inclusion bodies per 378 liters). We also found that Blankophor BBH alone had no obvious effect on the course of the disease in gypsy moth larvae that had previously ingested virus; it caused neither an increase in mortality, a decrease in time to kill, nor any obvious effect on the pattern of kill. Most larvae died between 18 and 29 d. Few larvae ingesting virus died earlier (13 to 17 d); however, about 5% of the larvae died later than 30 d after infection, which may be late enough to contribute to the second wave of mortality. A combination of Blankophor BBH at 0.5% and virus at 1011 inclusion bodies resulted in an increase in mortality and a decrease in time of kill compared with that seen for that level of virus without the enhancer, while eliminating the “tail” of mortality occurring 30 d after infection. However, a combination of Blankophor BBH at 0.5% and virus at 109 inclusion bodies still give higher mortality than expected with the virus alone, but did not decrease the time of kill or eliminate the “tail.”

Effects of nuclear polyhedrosis virus formulations on Lymantria dispar larval peritrophic membrane

1995 ◽  
Vol 53 ◽  
pp. 1010-1011
Author(s):  
K. S. Shields ◽  
J. D. Podgwaite
Keyword(s):  
Gypsy Moth ◽  
Lymantria Dispar ◽  
Wheat Germ ◽  
Nuclear Polyhedrosis Virus ◽  
Peritrophic Membrane ◽  
Lepidopteran Larvae ◽  
Occlusion Bodies ◽  
Food Particles ◽  
Polyhedrosis Virus ◽  
Nuclear Polyhedrosis

The peritrophic membrane is a continuous tube that encases the food in the midgut and hindgut of Lepidopteran larvae. It presumably protects midgut cells from abrasion by food particles, and perhaps acts as a barrier to infection. The gypsy moth, Lymantria dispar, is susceptible to a nuclear polyhedrosis virus (LdMNPV), which is transmitted per os. Once ingested, viral occlusion bodies (OB) dissolve in the alkaline midgut, liberating virions that ultimately invade susceptible cells. Recent studies have shown that selected stilbenedisulfonic acid derivatives administered in combination with LdMNPV significantly enhance viral potency, but the precise mode of action is unknown. We tested the effect of the stilbene derivative, Blankophor BBH (Burlington Chem. Co., Burlington, NC), on potency of LdMNPV in gypsy moth larvae, and determined the effects of ingested BBH/LdMNPV combinations on the surface structure of the peritrophic membrane.Newly molted second instar larvae were fed high wheat germ diet overlaid with either water, LdMNPV (102-106 OBs/ml), BBH (0.5%), or LdMNPV + BBH.

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