Spongy Moth Traps and Egg Mass Surveys

*A new common name for Lymantria dispar, spongy moth, replaced the prior name of this insect, gypsy moth, in 2022. Thank you for your patience and understanding as we transition through the name change process.​ For more information, visit the Entomological Society of America website.

The Wisconsin Department of Agriculture, Trade and Consumer Protection (DATCP) uses traps and visual surveys to monitor the spread of spongy moth* (formerly known as gypsy moth). We use the information from trapping and egg mass surveys to decide where to spray for spongy moth to slow their spread. We set traps according to a scientific grid system, using GPS technology.


Spongy moth traps do not control populations. They only measure population levels. We set them May-June, check them June-August, and remove them August-September.

Traps contain a plastic strip​ coated with pheromone, or the scent of the female moth, and are coated inside with a sticky substance. Males fly into the traps looking for a mate and become stuck. Traps catch only male moths.  

There are two types of traps. We set delta traps in areas where we expect numbers to be low, because they hold only 20 moths. We set milk carton traps where we expect higher numbers, because they can hold up to 1,500 moths.​


  • If you see a trap, do not disturb it.
  • If you find a trap on the ground, call th​e number written on it to report it. 
  • ​Allow trappers to place traps on your property and return to check and remove them.​
Delta Trap
Milk Carton Trap

Trappers will attempt to contact you if your property is within the grid, and ask permission to set the trap. If they cannot reach you, they will set the trap and leave information so you can call if you have questions. Wisconsin law does allow DATCP to go onto private property to inspect, investigate or control plant pests and diseases. See Wisconsin Statute 94.01.

We hire seasonal workers to set, check and r​emove spongy moth traps every year. Watch this website for application information in March.

Egg Mass Survey

Egg Mass SurveysWe conduct egg mass surveys in October and November in areas where we have trapped high numbers of male moths. This tells us where spongy moth are reproducing. Our own staff and some of the seasonal trappers do this w​ork, visually inspecting trees.​
Please allow egg mass surveyors onto your property. They will attempt to contact you to ask permission, and will leave information and a contact number if they cannot reach you. Wisconsin law does allow DATCP to go onto private property to inspect, investigate, or control plant pests and diseases. See Wisconsin Statute 94.01.

(Photo:​ Spongy moth egg mass, forestryimages.org)