Gypsy Moth

Gypsy Moth Trapping and Egg Mass Survey

The Wisconsin Department of Agriculture, Trade and Consumer Protection coordinates a statewide trapping program that provides a picture of where the moth is located. Trapping is not used as a method of population control. Trapping is a measuring tool.

Seasonal workers place traps at regular intervals in selected counties starting in late May. The trappers then check the traps for catches until the moths stop flying. Where gypsy moth is present, trapping can show us the extent of the population. Trapping also helps the program determine the effectiveness of spray treatments.

In October and November, we conduct egg mass surveys in areas of non-quarantine counties where we find high numbers of trap catches. Egg mass surveys help to identify areas where gypsy moths are reproducing. People in quarantine counties should contact their local suppression program coordinators to report egg masses or any gypsy moth life stage.

Finally, the trapping and egg mass survey data are analyzed to determine which areas in the western half of the state require aerial spray treatments.

Gypsy moth traps

Female gypsy moths do not fly. They use a pheromone (sex attractant) to lure male moths to them. Cardboard traps contain a pheromone strip to lure in the males, and the insides of the traps are sticky. So once the males are inside the trap, they stay there.

There are two types of traps: the delta trap and the milk carton trap—so named because it is shaped like a milk carton. A delta trap can hold up to 20 moths while the milk carton can hold up to 1,500 moths.

Trapping density

The number of traps set within an area depends on where it is located in the state. In the quarantine counties, where we know we will find gypsy moth, traps are set at one trap per 4 square miles or one trap per 9 square miles. In non-quarantine counties, trap densities are one trap per 1 square mile or one trap per 2 square miles.

Once a trap is placed according to a prescribed grid, the trap location is recorded using a handheld GPS (global positioning system) unit. GPS uses satellites to pinpoint the location of the trap. Throughout the trapping season, trappers then enter the number of moths captured into the GPS units. All the data is then downloaded and sent to program staff for analysis.

Gypsy moth trappers

Each year, DATCP hires a group of seasonal workers to set traps. A gypsy moth trapper must be able to read maps, enjoy working in the woods, be able to use a GPS unit and be able to keep detailed records. Trappers work for about 12 weeks from late May through September. Every March, a job description and application are posted on the website for downloading.

Egg mass surveyors

Once gypsy moth traps come down, a small group of trappers will become egg mass surveyors. They look for egg masses in targeted areas from mid-October to mid-November.

Trapping on private property

Trappers and egg mass surveyors are instructed to contact each resident before setting a trap on private property and to ask permission to set the trap. If the resident is unavailable, trappers are to leave an information sheet and a phone number for the homeowner to call for further information. Wisconsin law allows department staff or those authorized by the department to have access to any property to inspect, investigate or control plant pests and diseases. Chapter 94, Wisconsin Statutes.

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