Catherine W. Idzerda" />

Program highlights how to deal with gypsy moths

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Catherine W. Idzerda
Wednesday, August 6, 2008

Scientists call them lymantria dispar.

Homeowners call them gypsy moths—and a lot of other names we can't print in a family newspaper.

We can, however, tell you how to cope with the destructive pests.

At 7 p.m. Thursday, Rotary Botanical Gardens and UW Extension are hosting a session on preventing and reducing the damage from the moths.

"In the class, we're going to be covering the basics of what homeowners can do," said Mike Maddox, horticulture educator for the gardens and Extension.

Gypsy moths can seriously damage trees, but they usually don't kill the tree immediately.

"They place a lot of stress on trees," Maddox said.

Once a tree is under stress, it's easier for it to succumb to insect infestations, diseases or drought stress.

Gypsy moths start their lives as orange-yellow egg masses attached to trees, buildings, lawn furniture or any other place a mother moth finds convenient, according to Chris Williamson, UW-Madison turf and ornamental specialist.

The tiny larvas spend the winter inside the eggs. In spring, the caterpillars come out and start to feed on tree leaves.

Those caterpillars become pupa, then moths and the cycle starts all over.

It's the caterpillars that do the most damage, munching leaves like kids on a candy binge.

How do you know if you have gypsy moths?

"Oh, you'd know if you had them," Maddox said.

And here's something really creepy:

"You can hear them eating," said Anne Miller, Rock County land conservation specialist and gypsy moth coordinator.

Falling frass—that's the scientific word for poop—and the continual munching sounds like a light drizzle of rain.

Miller is in charge of tracking sightings and infestations and reporting to the Department of Natural Resources. In September, Miller and others from the land conservation department will respond to landowner reports and start surveying the county for egg masses.

"You have to have 20 contiguous acres and a minimum number of egg masses before they consider spraying," Miller said.

The fall survey will determine what areas will be sprayed the next May, when the bacterial insecticide bacillus thuringiensis kurstaki (Btk) is most effective, Miller said.

A similar form of bacillus thuringiensis is used to combat cabbage loopers in home gardens.

Pheromone flakes are sometimes used later in the season when male moths are looking for mates. The flakes confuse the males, making them unable to find the females.

Rock County Land Conservation doesn't participate in that program, Miller said.


UW Extension and Wisconsin Department of Natural Recourses specialists created a calendar showing the life cycle of the moth and how to eradicate it at different stages.

January to March: Larvae are inside the egg sacks, waiting for warmer weather. The larvae can survive inside the eggs to 20 degrees.

Scrape off the yellow-orange egg sacks into soapy water and leave them sit for two or more days. Or place them into a cup and microwave them for two minutes.

Do not scrape them off and leave the on the ground. The eggs will survive to hatch in the spring.

When temperatures are over 40 degrees, Golden Pest Spray can also be used on the egg masses, the DNR site said.

April: In late April, use a "sticky barrier band" around a tree to catch the tiniest caterpillars. Instructions on how to make a band can be found at

May: Aerial spraying is usually done in May. It's also not too late to put up a barrier band.

June and July: Place a burlap skirt around the trunk. The caterpillars move down into the grass during the day and back up to feed in the evening. They crawl into the burlap skirt and stay put. Catch the caterpillars and destroy them.

August to October: The moths emerge and lay eggs. The DNR recommends waiting until after the first frost to treat or remove eggs.

A tiny parasite insect, the ooencyrtus kuvanae, will use the egg masses for food.

November and December: Follow instructions for January to March.

Source: and

If you do have gypsy moths, talk with your neighbors to see if they've been impacted, too.

Then contact Anne Miller, Rock County land conservation specialist and gypsy moth coordinator, at (608) 754-6617, extension 118 or call the state hotline at 1-800-642-MOTH or 1-800-642-6684.


What: "Gypsy moths in Rock County," a program with Mike Maddox, UW Extension and Rotary Botanical Gardens Horticultural educator.

When: 7 p.m. Thursday Aug. 7.

Where: Rotary Botanical Gardens, 1455 Palmer Drive, Janesville.

Cost: $5.

For more information: Call (608) 752-3885 or go to

Last updated: 10:03 pm Thursday, December 13, 2012

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