Gypsy Moth In North America

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Gypsy Moth Nucleopolyhedrosis Virus

Viral disease, sometimes referred to as "wilt", is naturally ocurring in virtually all gypsy moth populations. The Disease is caused by a nucleopolyhedrosis virus (NPV). This name is derived by the existence of a a matirix of polyhedral protiens that surround the viral DNA. These polyhedra are large and can be seen under a light microscope.

Infection occurrs when caterpillars eat foliage contaminated with viral oclusion bodies. This pathogen invades through the gut wall, reproducing rapidly in internal tissue causing the disintegration of internal organs and the death of the host caterpillar. Eventually, the host ruptures, distributing viral oclusion bodies into the environment which serve to infect other individuals.

Virus particles can persist in the soil. Virus can persist in low density gypsy moth populations but causes very little mortality when populations are low. However, when gypsy moth populations are high, massive propogation of virus occurrs, resulting in very high levels of host mortality. This phenomenon is called an "epizootic" and is the most common cause of the collapse of high density gypsy moth populations.

There has been considerable research that has gone on to develop the gypsy moth NPV as a biological pesticide. This material, referred to as "Gypchek" is currently used in limitted quantities for suppressing gypsy moth outbreaks.

Gypsy moth virus life cycle: viral occlusion bodies (OB) (A) dissolve in the insect's gut liberating nonoccluded virus (NOV) that enters the midgut (B) and eventually passes through to the hemocoel. There NOV enters hemocytes and other cell types and replicates (C), producing more NOV (D) and OB (E). Cells eventually rupture releasing NOV and OB into the hemocoel. The insect dies (F) 10-14 days after consuming the virus.

(photo from Reardon, Podgwaite, Zerillo. 1996. Gypcheck - The Gypsy Moth Nucleopolyhedrosis Virus Product. USDA FS FHTET-96-16.)

Virus killed gypsy moth larva.

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Last modified 10-29-03 by Sandy Liebhold .

USDA Forest Service - Northeastern Research Station