Gypsy Moth

NPV or Gypchek

NPV stands for nucleopolyhedrosis virus. It is a virus that occurs naturally wherever gypsy moth is present. Gypchek is a biological pesticide product we use that contains NPV. This insecticide only infects gypsy moth caterpillars.

When gypsy moth caterpillars ingest leaves with NPV, it stops eating and dies within a week to 14 days. Only one application of NPV is needed.

When will NPV spraying begin?

We usually begin spraying NPV in southern Wisconsin in May and move northward, finishing in early June. Planes take off at sunrise.

In urban areas during the school year, we will not spray between 7:15 and 8:30 a.m.

Why must planes spray so early in the day?

We need the high humidity and low winds of early morning to assure the spray does not evaporate or blow away. The planes continue spraying as weather conditions allow and/or when the area is finished. This may mean spraying into the late morning or afternoon, if possible.

Is NPV harmful to humans?

Numerous laboratory and field studies over the past 30 years have shown that NPV presents no known risk to humans. NPV is a powder made of gypsy moth caterpillars and virus particles. NPV is mixed with a liquid that contains starches, sugars and tree cellulose. People can stay indoors or leave the area until spray is done if they feel more comfortable.

Is NPV harmful to animals?

NPV will not harm animals, but the low-flying planes may frighten pets or livestock. It is recommended to keep animals inside, if possible.

Fast Fact sheet about NPV - 1 page PDF (You will need a PDF reader to view this document.)

For more information, call toll free 1-800-642-6684 and select option 3, or e-mail gypsymoth@wisconsin.gov.