MADISON, WI (SPECTRUM NEWS) — After three years of decline, Gypsy Moth populations rebounded in 2020 in Wisconsin. 

Gypsy Moth are an invasive species to the United States, with no natural predator or population check. They devour leaves on trees, sometimes killing the trees, then harming forrest health and having other economic impacts on the state.

“Timber, nursery, tourism industries, those can all be negatively affected by increases in gypsy moth and damage as well,” said Michael Falk, Gypsy Moth trapping coordinator with the Wisconsin Department of Trade, Agriculture, and Consumer Protection.

From 2017 to 2019, moth populations were cut in half in Wisconsin. In 2020 the population increased 60% compared to last year.

The weather played a large role.

“From 2017 to 2019 we saw two winters that consecutively had kind of brief, but intense periods of cold that was sufficiently low enough to kill the eggs that were present for Gypsy Moth,” Falk said.

Not all of the eggs Falk said, but a substantial portion. A more mild winter allowed them to rebound this year, but at least it was rebounding from low levels.

“While the population did increase by 60%, it increased from a very low point,” Falk said.

People throughout Wisconsin can help DATCP control populations.

“I'd say overall the best thing people can do is familiarize themselves with gypsy moth in general,” Falk said.

Resources for identifying moths at different times of year are available on DATCP's website or the websites of the agency's partners. 

The Moths have a single-year life span, meaning they will hatch in the spring and lay eggs in the fall.

Right now, Moths are in egg masses and if you see one on your property you can destroy it by burning it or putting it in soapy water.

Or call DATCP's gypsy moth hotline at 800-642-MOTH or email gypsymoth@wisconsin.gov.

DATCP especially wants to know if you find one in the western third off the state, where populations are not yet established.

“The western third of the state is area that has not been heavily infested by gypsy moth yet and we are trying to keep it that way as long as possible,” Falk said.

The western border of where Gypsy Moth have established in the U.S. Runs through Wisconsin.

DATCP's primary population control efforts come when moths are mating, they spray the same pheromone the female moths use to attract males in areas where the insects are known to be.

“If the pheromone is coming from everywhere then they can't pinpoint where the female is,” Falk said.

The spray doesn't kill the moths or any other wildlife, but can cut down on reproduction of them.